ASTRONOMY AND ASTROPHYSICS

Table of contents :

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Milky Way galaxy space vehicles space tourism Big Bang g-ray bursts telescopes comets antrigravity supernova exobiology

the solar systems Sun Earth Moon Mars Saturn Titan extrasolar planets black holes

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• Wherever matter concentrates in the vast vacuum of space, chances are you will find a disk. Simple physics makes it so; all you need is a spinning sphere of matter collapsing under its own gravitational pull. As the core contracts, it rotates faster to conserve angular momentum. This spin causes the matter around the core to fall onto the equatorial plane, forming a flattened disk of gas and solids. Angular momentum creeps outward, keeping the core from breaking apart. Meanwhile, disk material moves inward along the equatorial plane, eventually either feeding the core or forming other orbiting objects around the core. That oft-repeated scenario makes disks essential building blocks of the universe. This special section covers the many different flavors of disks in space and what they can tell us about the formation of everything from giant gas planets to galaxies. The solar system got its start when a molecular cloud collapsed to form the Sun and a circumstellar disk of gas and dust. Chondritic meteorites contain primordial dust from other nearby stars, evidence that the Sun formed within a cluster of stars^ref. At the edge of the solar system, where remnants of the circumstellar disk are dispersed in the Kuiper belt. The belt is more extensive and more structured than previously thought, and its structure holds clues to planetary formation, planetary migration, possible rogue planets, and the close passage of other stars^ref. Over the past decade the search for circumstellar disks with possible planets around other stars has intensified. Planets around Sunlike stars are now considered to be ubiquitous^ref. Current models of planet formation require a disk full of gas and dust to swirl and sway around the star long enough to accrete giant gas planets. Observations of the different stages of the evolution of circumstellar disks are helping to refine these models. For decades, astrophysicists thought that disk-shaped spiral galaxies turn into featureless balls of stars when they collide with other galaxies. The spirals (which include our own Milky Way galaxy) can be surprisingly resilient^ref. Meanwhile, other astronomers are probing how disks of matter pulled from a companion star trigger the nuclear explosions that turn white dwarf stars into type Ia supernovas^ref: cosmic flares that help gauge the expansion of the universe. The most illuminating evidence for black holes is the accretion disks that surround them^ref. As a black hole accretes gas, the gas radiates and provides a thermal signature of the mass, rate of spin, and location of the event horizon of the black hole. This quick tour of disks in space highlights their simplicity and ubiquity. As modeling and observations continue to provide more details of disk complexity, their utility for resolving fundamental mysteries of space, such as planet formation and black hole jets, will grow.
• Our Milky Way galaxy looks quite different from an ordinary spiral galaxy, astronomers say, after conducting what they call the most comprehensive structural analysis ever done of the galaxy. The Milky Way is no ordinary spiral galaxy. According to a massive new survey of stars at the heart of the galaxy, the Milky Way has a definitive bar feature -- some 27,000 light years long -- that distinguishes it from ordinary spiral galaxies, as shown in this artist's rendering. The small yellow arrow points to our Sun. The survey sampled around 30 million stars to build a portrait of the galaxy's inner regions. The survey gives fine details of a long, central bar feature that astronomers say distinguishes the Milky Way from more usual spiral galaxies. This is the best evidence ever for this long central bar in our galaxy. Using NASA’s orbiting Spitzer Space Telescope, astronomers surveyed some 30 million stars in the plane of the galaxy in an effort to build a detailed portrait of the inner regions of the Milky Way. The task is like trying to describe the boundaries of a forest from a vantage point deep within the woods: this is hard to do from within the galaxy. Spitzer’s capabilities, however, helped the astronomers cut through obscuring clouds of interstellar dust by gathering infrared light, a type of light which penetrates these clouds. This provided information on tens of millions of stars at the center of the galaxy. The new survey gives the most detailed picture to date of the inner regions of the Milky Way. We’re bringing tens of millions of objects into the equation. The possibility that the Milky Way Galaxy has a long stellar bar through its center has long been considered by astronomers, and such phenomena are not unheard of in galactic taxonomy. They are clearly evident in other galaxies, and it is a structural characteristic that adds definition beyond the swirling arms of typical spiral galaxies. The new study provides estimates for the size and orientation of the bar that are far different from previous estimates. It shows a bar, consisting of relatively old and red stars, spanning the center of the galaxy roughly 27,000 light years in length. This is 7,000 light years longer than previously believed.  The analysis also suggests the bar is oriented at about a 45° angle relative to a line joining the sun and the center of the galaxy. Astronomers have debated whether a presumed central feature of the galaxy would be a bar structure or a central ellipse—or both. The new research clearly shows a bar-like structure. To date, this is the best evidence for a long bar in our galaxy. It’s hard to argue with this data. The Spitzer Space Telescope went into orbit in August, 2003. NASA’s Jet Propulsion Laboratory in Pasadena, Calif., manages the telescope (Benjamin, Astrophysical Journal Letters)
• The cold dark matter model has become the leading theoretical picture for the formation of structure in the Universe. This model, together with the theory of cosmic inflation, makes a clear prediction for the initial conditions for structure formation and predicts that structures grow hierarchically through gravitational instability. Testing this model requires that the precise measurements delivered by galaxy surveys can be compared to robust and equally precise theoretical calculations. Here we present a simulation of the growth of dark matter structure using 2,160³ particles, following them from redshift z = 127 to the present in a cube-shaped region 2.230 billion lightyears on a side. In postprocessing, we also follow the formation and evolution of the galaxies and quasars. We show that baryon-induced features in the initial conditions of the Universe are reflected in distorted form in the low-redshift galaxy distribution, an effect that can be used to constrain the nature of dark energy with future generations of observational surveys of galaxies^ref.
• gravitational lensing : warped space seems to magnify light as well as bending it, in just the way that Einstein predicted, scientists have found. The discovery of a slight brightening of 200,000 distant quasars finally confirms a theory posited by Einstein > 90 years ago. According to Einstein's picture of the Universe, mass warps the fabric of space that surrounds it. Light from a distant star travels in a straight line along this fabric, but because it is slightly bent around heavy objects such as galaxies, the star's position when viewed from Earth is shifted^ref. This effect has been confirmed many times through observation. But bending light is only part of the story. Lenses also magnify images, and astronomers have been searching for a cosmic magnification of distant objects for decades. No one had been able to reliably detect the magnification part of the lensing signal. Scranton led the project from the Apache Point Observatory in Sunspot, New Mexico, which is the base for a broader project called the Sloan Digital Sky Survey (SDSS). Their results, which show a brightening of distant objects on the order of 1%^ref. The discovery also confirms that the Universe is full of dark matter. > 80% of the mass in the Universe is thought to be dark matter, the unseen material that seems to hold galaxies together. The amount of magnification seen by the SDSS team ties in perfectly with the predictions of current dark-matter models. The quasars observed by the SDSS project are about 10 billion light years away. Quasars are amongst the brightest objects in the Universe, and are thought to be distant galaxies that have a supermassive black hole at their centre. As matter accelerates into the black hole, it sends out powerful beams of radiation that can be seen from Earth. Quasars are an ideal way to watch for cosmic magnification, because they are distant enough to have their light bent by many massive objects before they reach Earth. Light travels to us on a very bumpy road from these quasars. They also produce enough light for scientists to measure small changes in their brightness very precisely. Previous groups have been able to measure the brightening of a much smaller sampling of quasars. But those results showed a brightening that was too large to fit with either Einstein's ideas or the dark matter model. This led many to think the results were skewed by errors in the sensitive measurements. Now that seems to have been cleared up. This measurement agrees with what the rest of the Universe is telling us, and the nagging disagreement is resolved. Using a huge sample of quasars was the key to ironing out these errors. The team hopes to use cosmic magnification to study how galaxies and dark matter interact with each other.


• it's a hard life being the fastest star in the galactic suburbs. One minute you're waltzing around your companion, the next you're flung outwards by a black hole so fiercely that you're all set to be the first star to leave the Milky Way. "We have never before seen a star moving fast enough to completely escape the confines of our Galaxy," says Warren Brown, part of the team at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, who spotted the 700 km/s star. It is the swiftest star ever spotted in the outskirts of our galaxy, travelling at twice the speed needed to escape from the Milky Way. Runaway stars have been seen before, but the previous record-holder was seen travelling at a mere 490 km/s, and all of them are still confined in our Galaxy. The new speedster is called SDSS J090745.0+024507, but researchers were tempted to call it the outcast star^ref. The astronomers believe that the star once had a companion. But as the pair twirled around each other they waltzed too close to the Milky Way's central black hole and the companion was trapped there, flinging the outcast away like a stone from a slingshot. The star is rich in elements heavier than hydrogen and helium, making it characteristic of stars formed in the central regions of the Milky Way. The star is now in the outer reaches of the Galaxy, almost 200,000 light years from Earth, and is moving directly away from the Galactic Centre. The scientists believe that it has been on its present course for < 80 million years; it may be 80 million more before it clears the edge of the Galaxy and hurtles into intergalactic space. The team used initial observations from the Sloan Digital Sky Survey to spot potential high-speed candidates, and then tracked them with the Multiple Mirror Telescope, perched atop Mount Hopkins near Tucson, Arizona. Almost 20 years ago, Jack Hills, an astronomer at Los Alamos National Laboratory in New Mexico, proposed that this galactic slingshot mechanism could create 'hypervelocity' stars. There may be up to 10,000 more hypervelocity stars in our Galaxy. If dozens of these stars were tracked, astronomers could learn about the rate of star formation in the core of the Milky Way. Plotting their trajectories accurately could reveal the gravitational influence of hidden dark matter in the Galaxy
• the Universe's first stars were born a mere 700 million years after the Big Bang, far earlier than researchers previously thought. The discovery comes from images of stars in galaxies that are so far away their light has taken some 13 billion years to reach us. What's more, the images show that these early galaxies were surprisingly heavy, with as much as a quarter of the mass of galaxies that developed later, such as our Milky Way. Using NASA's Spitzer Space Telescope to collect infrared radiation from 2 of the most distant galaxies known, both found in the constellation Fornax in the southern skies, given the Universe's estimated age of 14 billion years, the team deduced that the galaxies look the way they did just a billion years after the Universe came into being. This is the first time that old stars have been seen in such a distant object : the stars in the images are already well developed. The stars are about 300 million years old in the images, meaning that they were born when the Universe was just 700 million years old. The orbiting Spitzer Space Telescope, launched in 2003, is the first telescope sensitive enough to allow an analysis of the infrared radiation from these stars. The galaxies' masses were estimted by comparing their spectra with models of spectra from galaxies with a known number of stars. Popular models of galaxy formation assume that the early Universe contained only very small galaxies, so this will cause theorists to think very hard, but such large galaxies could be the exception rather than the rule. Numerous lower-mass galaxies are predicted at the same epoch. Because large galaxies might be the only objects visible at great distances, there could be many smaller galaxies going undetected. That question may be settled by NASA's James Webb Space Telescope, which is much more sensitive and scheduled for launch in 2011.
• The birth of stars involves not only accretion but also, counter-intuitively, the expulsion of matter in the form of highly supersonic outflows. Although this phenomenon has been seen in young stars, a fundamental question is whether it also occurs among newborn brown dwarfs: these are the so-called 'failed stars', with masses between stars and planets, that never manage to reach temperatures high enough for normal hydrogen fusion to occur. Recently, evidence for accretion in young brown dwarfs has mounted, and their spectra show lines that are suggestive of outflows. Spectro-astrometric data have been reported that spatially resolve an outflow from a brown dwarf. The outflow's characteristics appear similar to, but on a smaller scale than, outflows from normal young stars. This result suggests that the outflow mechanism is universal, and perhaps relevant even to the formation of planets^ref.
• Andromeda, the nearest large galaxy, has been found to be almost 3 times wider than astronomers thought. Previous estimates had suggested that the spiral galaxy, also known as M31, was about 75,000 light years across. That is slightly smaller than our own galaxy, the Milky Way, which is 100,000 light years wide. But a project to map the movement of about 3,000 stars in Andromeda's distant outskirts has found that, surprisingly, they too are orbiting the galactic centre in the same plane as the rest of the galactic disk. Because this movement makes them members of Andromeda's stellar posse, astronomers have redrawn its perimeter to include them, boosting the galaxy's diameter to more than 220,000 light years. This will force theorists to reassess how such galaxies form. This discovery will be very hard to reconcile with computer simulations of forming galaxies. Within the boundary of a galaxy, matter orbits the galactic centre in an orderly disk. But Andromeda has an extended, clumpy halo of stars that are thought to have been left in the neighbourhood by galaxies that passed by and collided with its outer stars. Astronomers assumed that the force of these collisions would have left these stars buzzing around in random directions, and so didn't count them when measuring the galactic diameter. To check, researchers used the Keck telescopes in Hawaii to observe these stellar outsiders. Andromeda is the most remote astronomical object normally visible to the naked eye. It lies about 2 million light years from Earth. On one side of Andromeda's disk, light from the stars is redshifted: it is stretched to longer wavelengths as they move away from the Earth. But on the other side, the stars' light is blueshifted to shorter wavelengths as they move towards us. By calculating the difference between the shifts, the astronomers conclude that the outer stars are actually orbiting around the centre of the galaxy, and are therefore part of it. The clumps of outer stars left from galactic collisions should not, according to current models, get roped into Andromeda's disk. You just don't get giant rotating disks from the accretion of small galaxy fragments. Similar observations of other galaxies should be made to work out if this sort of extended disk is unique to Andromeda^ref

Web resources : Scott Chapman's Andromeda page
• Researchers have snapped a picture that catches a star in the act of capturing material from its companion. The image shows a bridge of gas streaming from a red giant, called Mira A, towards a nearby collapsed white dwarf, called Mira B. Researchers had a good idea that the white dwarf was probably sucking up material cast off from Mira A by its own stellar wind. But the visible bridge of material between them indicates that the white dwarf is also capable of snatching material straight out of the heart of Mira A. The bridge shows that there's actually matter flowing from the red giant towards the red dwarf.  Scientists at NASA's Chandra X-ray Observatory in Cambridge, Massachusetts, used information from the Hubble Space Telescope to locate this star system, which lies 420 light years from Earth. The stars sit about 6 billion km apart from each other, which is roughly twice the distance of Pluto from the Sun. The picture reveals X-ray radiation, rather than visible light. X-rays are produced by the star system as rapidly moving gas particles collide in the stream between the 2 stars^ref.
• We'll never find a star larger than about 150 times the size of our Sun, according to observations of a star cluster at the centre of our Galaxy. Astronomers have previously been unable to agree whether stars have a natural limit to their size, or what that limit might be. Theoretical estimates based on the turbulent dynamics of stars' guts have ranged from 10 to 1000 solar masses. The stars of the Arches cluster, discovered in the early 1990s, collectively have about 11,000 solar masses, making it the most massive star cluster in our Galaxy. If there were no limit to how big stars can grow, you'd expect ones up to 500 times our Sun's mass to be found in this dense cluster of stars. But no stars larger than about 130 solar masses was found. Mindful of limits to the accuracy of these observations, a reasonable upper limit to a star's mass is about 150 solar masses. This results indicates there is only a 1 in 100 million chance that stars have no upper limit to their mass. A galaxy's mass is estimated from the amount of light it produces, but this requires an assumption about the size distribution of its stars. That assumption often changes with each new theoretical treatment of the problem : at least now there is a firm number based on evidence. Although astronomers have claimed to see more massive stars, they always turn out to be a group of stars, or have huge uncertainties about their mass. A star > 150 solar masses could possibly exist briefly if 2 other stars collide. But of course this is a very violent process, and it's not going to live very long. A similar cut-of was found in a more distant star cluster, although that result was less statistically significant. Theoreticians should now focus on working out why stars have this mass limit In the late 1910s, the English astronomer Arthur Eddington suggested that growing stars might reach a point where the pressure of radiation coming from their cores was greater than the gravity keeping the outer layers held fast. At this point, stars could accumulate no more material, putting an upper limit on their mass. Alternatively, turbulence in the outer atmosphere of the largest stars could be enough to throw off material faster than fresh matter can accrete. The latest theoretical estimates from this model put the star's upper limit at around 120 to 150 solar masses, agreeing with this experimental observations^ref
• space vehicles
• Europe's reputation for rocket engineering got a boost with the successful launch of the Ariane 5 ECA at 21:03 GMT on 12 February 2005. The 50-metre high rocket is Europe's largest, able to deliver up to 10 tonnes of payload into orbit around Earth. But its maiden voyage on 11 December 2002 ended in disaster when the vehicle veered dangerously off course and self-destructed just minutes into the flight. The successful flight means that the ECA, operated by the company Arianespace of Courcouronnes, France, should begin to attract commercial customers. Each flight can carry several satellites into orbit, reducing the costs of each instrument's launch substantially. The first commercial flight is expected within the next 6 months. The ECA will replace the Ariane 5G 'generic' rocket, which is limited to carrying one satellite at a time. The ECA carries more fuel, and has had each of its engines beefed up: the main stage produces up to 20% more thrust. The rocket carried 3 different payloads on this launch. After 26 minutes of flight, the Ariane 5 ECA released a 3,600-kilogram communication satellite called XTAR-EUR into orbit. 2 other satellites built by the European Space Agency were also on board. One is called Sloshsat-FLEVO (Facility for Liquid Experimentation and Verification). This 129-kg craft is designed to help us understand how spacecraft can be destabilized by liquid fuel sloshing around inside their tanks in microgravity. The third satellite, Maqsat B2, was not deployed by the rocket. Instead, it provided an extra 3.5 tonnes of weight to prove ECA's lifting capabilities, and sent essential data about the whole flight back to mission controllers

Web resources : Kourou Spaceport
• Pioneer 10 and 11 were launched in 1972 to explore Jupiter and Saturn. After their studies there were done, they continued on towards the edge of the Solar System. But since around 1980, when they passed beyond the orbit of Uranus, the radio signals that they send back to Earth have been shifted to progressively shorter wavelengths, implying that the spacecraft are decelerating very slightly on their outward journey. It could just be some unforeseen effect generated onboard the probes themselves, by leakage of gaseous fuel from the thrusters, for example. But if it is not, then this deceleration (dubbed the Pioneer anomaly) might point to a gap in our understanding of the fundamental principles of physics. It could reveal the influence of a new force, or perhaps a new kind of matter. That would be a revolutionary finding, but even the more mundane explanation of an onboard instrumental effect would be very important because it would force space engineers to rethink their methods for very precise navigation in space. Sending a mission after the Pioneer craft would allow scientists to confirm whether the Pioneer anomaly is real, and to rule out some of the technological explanations^ref. The mission would need to have very accurate navigation, and instruments that could detect the tiny deceleration and potential causes such as leaking gas. And to get an answer in the next couple of decades would take a fast-travelling probe, one faster than the Cassini spacecraft currently orbiting Saturn. That planet is only half as far away as Uranus, but it still took Cassini 7 years to reach its destination. Instead of relying on conventional rocket fuel, the craft might use the faster propulsion systems being investigated by NASA and the European Space Agency (ESA), which involve nuclear power. The first of these craft is likely to be NASA's Jupiter Icy Moons Orbiter, scheduled to launch around 2015. But none of the currently proposed missions could probe the Pioneer anomaly as they stand, because they will not have sufficiently accurate navigation or instruments. So the researchers are arguing for a spacecraft that draws on the lessons learnt from the Pioneer missions, in which various accidents of design have made it possible to track the spacecraft's movement very closely. It could be developed in 5 years and flown early in the next decade. Adding instrumentation to missions already planned might be a more realistic option, which could cost as little as US$70 million. Both Pioneer spacecraft are now too far away for their weakening communications systems to make further contact with Earth. Pioneer 10 was last heard from in early 2003, and is now > 12 billion km away. It is heading for the giant red star Aldebaran in the Taurus constellation, but it won't get there for another 2 million years.
• scramjet (supersonic-combustion ramjet) engines, which, like a conventional jet engine, burns fuel using air sucked in from the atmosphere. In conventional engines the fuel cannot burn properly at high speeds because the oxygen whips by too quickly. Ramjets use the speed of the craft to compress air and heat it up, allowing their hydrogen fuel to burn more quickly. But scramjets only work when the craft is travelling faster than sound, making it difficult if not impossible to test in the lab : $230-million Hyper X programme
• scientists from the University of Queensland made a successful scramjet test flight in 2002 with a project called Hyshot. Their rocket did not have any wings, making it easier to control at speeds of Mach 7, but ultimately impractical for use in a vehicle. Although scramjets travel at immense speeds, they are not appropriate for most applications. The engines heat up to about 1000ºC. And craft travelling at that speed need hefty additional insulation to withstand the heat from air friction. Sonic shock waves also tend to reduce lift at high speeds, making it hard to keep the jet airborne. Put all these problems together and hypersonic flight just does not look like a good commercial prospect : we won't see passenger flight using this technology
• NASA's X-43A experimental unmanned aircraft :
• in June 2001, was blown up by flight engineers when they lost control of the craft shortly after it was released from the aeroplane
• on Sat Mar 27 2004 it flew under its own power for 10", reaching speeds > 2 km/s = Mach 7, or 7 times the speed of sound. The previous record-holder for jet-propelled flight was the US military's SR-71 Blackbird, which flew at 3.3 times the speed of sound. The X-43 A looks more like a missile than a plane, being too small to carry a passenger. The 3.6 m by 1.5 m jet was flown by remote control from the ground : an aeroplane carried the craft to an altitude of 12,000 m, from where it was lifted to 30,000 m on the back of a booster rocket. Once set free, it screamed through the atmosphere under its own power for 10". After a further 6' of gliding, it splashed into the Pacific Ocean. Rocket boosters can already travel much faster than Mach 7, but they must carry both their fuel and a source of O₂, reducing their cargo capacity and making them unlikely to be of use to a plane.
• on Nov 16 2004, it flew at nearly 10 times the speed of sound, breaking its own speed record. The unmanned X-43A aircraft reached speeds of roughly 11,000 kilometres per hour, flying under its own power for about 20 seconds. The X-43A was strapped to a Pegasus booster rocket and carried from Edwards Air Force Base, California, under the wing of a B-52B aeroplane. The plane released its cargo at an altitude of about 12 km, and the booster rocket blasted the craft up to 33.5 km. At this point the X43-A was already travelling at about Mach 9, then the booster fell away and the craft accelerated to close to Mach 10 using its own engines. It eventually travelled for > 1,000 km before splashing into the Pacific Ocean. Its flight had been delayed on Nov 15 while engineers made last minute adjustments to onboard instruments. The X-43A is little more than an engine with wings, and is 3.7 m long by 1.5 m wide. Unlike conventional jet engines, a ramjet engine uses its own speed, rather than rotating blades, to force air into its combustion chamber, where the oxygen reacts with hydrogen fuel. And in a scramjet, such as the X-43A, this combustion happens when air is forced in at supersonic speeds. This means that the engine only begins to work past Mach 4, making ground-based tests virtually impossible. Although NASA's rockets can fly faster than the X-43A, they must carry both hydrogen and oxygen, a combination that would be too risky and expensive for a commercial plane and that also reduces the craft's cargo capacity. Once ignited, rockets tend to burn continuously at full thrust, but the X-43A's engine can varying its power, allowing it to fly more like an aeroplane. Some engineers believe that scramjets could eventually allow passenger aircraft to fly around the world in just a few hours, although it would take decades of further research to achieve this. Still, in the near future scramjets might be adapted to deliver cargo into low Earth orbit. The Hyper X programme itself has been scrapped, however, since NASA's efforts were redirected to manned space flight after President George W. Bush outlined his 'Vision for Space Exploration' in January 2003. Engineers will now focus on building a replacement for the space shuttle fleet, due to be phased out in 2010
Web resources :
• Dryden Flight Research Centre (DFRC) - HyperX
• NASA's Hyper X project
• US History of Hypersonic Flight
• NASA: First Supersonic Flight
• Centre for Hypersonics
• return and rescue space systems (RRSS) : an inflatable lifeboat could one day ferry stranded astronauts back to Earth. The re-entry vehicle weighs just 130 kg and is being developed to carry cargo back from the International Space Station (ISS), but its inventors believe that it could also let astronauts bail out of the space station, or deliver robots to the surface of Mars. Inflatable spacecraft are not a new idea - NASA developed one in the 1960s - but they have never seen active duty. RRSS's craft, which has so far taken US$2 million and 6 years to develop, has been tested twice before, in 2000 and 2002. In the last test, the pod failed to detach from its rocket; the craft has been redesigned to solve this problem. The latest prototype will launch on a rocket from a Russian submarine in the Barents Sea off Murmansk. At about 200 km up (the equivalent of a low-Earth orbit) the ship will detach and inflate, then spend 200 or so falling to Earth, eventually landing, the team hopes, on Russian soil in Kamchatka. The demonstration vehicle is shaped like a shuttlecock, and is just over 3 m across. It carries pressure sensors and other equipment to monitor its descent. It will inflate using tanks of nitrogen, but RRSS hope eventually to use the same chemical reaction used in car airbags, which generates nitrogen gas from a powder. An inflatable heat shield will protect the ship and slow it down. A second, larger inflatable emerges from the rear of the craft to act as a parachute, reducing its speed to about 35 kilometres per hour before it hits the ground. The surface is made from a tough, flexible polymer coated with a paint that can withstand temperatures of around 900 °C. The exact composition of the paint is a closely guarded secret. The lifeboat could not help astronauts escape a stricken space shuttle, as the shuttle's design would prevent it launching. It may, however, be incorporated into the next generation of vehicles to replace the shuttle, and is one of several possibilities being considered by NASA.
• a metallic mutt, nicknamed Boudreaux, is officially called the Extra Vehicular Activity Robotic Assistant. It runs on 4 wheels and is about the size of a small golf cart, similar to the Mars exploration rovers Spirit and Opportunity. Tests conducted in the middle of the Utah desert in April 2004 proved that Boudreaux can follow a pair of astronauts at walking pace, carrying tools, geological samples or analysis equipment for them. It is nearly autonomous, able to plan a route for itself through rocky areas, but it also responds to voice commands, obediently trundling over to where an astronaut is working. It can even tell the astronauts where it is. With stereovision cameras to relay pictures of the astronauts back to a control centre, it will also allow mission commanders to keep a watchful eye on interplanetary explorers. Boudreaux has a dextrous arm that can pick up rock samples or dropped tools, tasks that are tricky for an astronaut wearing a bulky, inflexible space suit. On a long mission, the robotic dog would also be a lighter load for a spacecraft than a human with accompanying gear. Its tracking system currently works using a global positioning system (GPS), so the astronauts would need orbiting satellites on whatever planet they visit for the rover to work best. But as a back-up, Boudreaux can also use on-board cameras to navigate. As it could be 15 years or more before humans return to the Moon, Boudreaux will be ready to go into space before we are. The robotics team at Johnson Space Centre are better known for Robonaut, a humanoid robot designed for space walks that was unveiled in 2000.
• The Russian-built oxygen generator in the International Space Station (ISS), called Elektron, mysteriously shut down on 8 September 2004. The current crew, American Mike Fincke and Russian Gennady Padalka, have been unable to get it going again for more than a few hours at a time, despite numerous salvage attempts. NASA stresses that Fincke and Padalka are not in immediate danger. They have back-up oxygen, in the form of spare canisters and oxygen-releasing 'candles', to last another 140 days, which is long beyond their scheduled return. But the Elektron unit's failure opens up the possibility that the next crew in line, US astronaut Leroy Chiao and Russia's Salizhan Sharipov, will not get the chance to replace the current team. If that happens, the space station may never be fit to live on again. If it is not continuously inhabited, its habitability is seriously damaged. If the station was left uninhabited, space scientists could be left with their research plans in ruins. The space station was conceived as an orbiting lab that would play host to a range of scientific experiments. But because of setbacks, not least the Columbia shuttle disaster in February 2003, the station is staffed by a skeleton crew who can do little more than day-to-day maintenance. Denied its primary transport vehicle since the crash, the space station currently relies on Russia's Soyuz capsules to ferry crew and on Progress vessels to deliver cargo. Neither has the carrying capacity of the shuttle. The European Space Agency's Columbus lab module, for example, is still awaiting launch and is now in danger of never making it into space at all. But the aftermath of the shuttle disaster is not the only reason for the station's difficulties : the United States may be turning its back on the space station, even if it overcomes its current problems. President George W. Bush has famously announced that he wants to see an American on Mars, a plan that would not involve the space station. The plan seems to be to phase out the space station by 2010 or thereabouts. If the United States wants to get to Mars, it will need to start by developing a fresh programme to go to the Moon, bypassing the stranded station on the way. If the United States does give the space station the cold shoulder, its collaborators including Russia, Japan and Europe will not be impressed. They have all spent vast sums on the project, and would not appreciate being left in the lurch
• an experiment aboard the International Space Station will check the theory that imminent earthquakes can be spotted from space. Researchers hope that tracking changes in the radiation belts that blanket the globe will give them early warning of tremors hundreds of kilometres below. If successful, the work could help pave the way for a system of satellites that watch for earthquakes. Seismologists know that the rumblings that precede an earthquake cause disturbances across a wide range of frequencies that can be picked up by radio antennae. These disruptions are thought to result from the opening of tiny cracks in the rocks as they begin to deform. Monitoring these effects on the ground would require a huge, global network of antennae. Fortunately our planet has a natural version of such a net: bands of charged particles trapped in Earth's magnetic field, called Van Allen belts. These belts are best known for shielding the atmosphere from cosmic radiation. Electromagnetic disturbances may be detectable in the Van Allen belts before an earthquake occurs. The study is called Lazio-Sirad. But no one has yet been able to show that the effect can be spotted within the useful time frame of a few hours before an earthquake. The International Space Station, cruising some 370 km above Earth, grazes the lowest Van Allen belts at certain points in its orbit, providing a useful vantage point for observation. The Lazio-Sirad experiment will monitor the number and direction of charged particles in these belts for at least one week, and possibly for up to 6 months. They will then try to correlate variations in this particle flux with natural events. Slow variations are expected to be caused by solar flares, and rapid changes are expected in response to seismic activity. The project began as a fresh crew arrived at the International Space Station on 15 April 2005, including astronaut Roberto Vittori, who will oversee the experiment. If the theory proves to be true, then our planet's rumblings could one day be monitored from space. This is the hope and dream, but first we have to check that what has been hinted at is real. So far, evidence is still scarce
• NASA's space-shuttle fleet has not flown since Columbia broke up while re-entering the Earth's atmosphere on 1 February 2003, killing 7 astronauts. The Columbia Accident Investigation Board (CAIB) reported later that year that NASA's management culture was as much a cause of the accident as the piece of falling foam that struck the shuttle's wing during lift-off. NASA has restructured itself since then, while working intensively on ensuring that the remaining shuttles, Discovery, Atlantis and Endeavour, are safe to fly again. After 4 of the major facilities involved in getting the shuttles ready for space were battered by hurricanes in August and September 2004, NASA now hopes that Discovery space shuttle will set off on mission STS-114 between 12 May and 3 June 2005. Samples of moss aboard the doomed space shuttle Columbia have survived to reveal an unusual growth pattern that gives clues to the plant's evolutionary history. Samples of common roof moss (Ceratodon purpureus) grown in darkened containers on the shuttle put out wispy fronds in clockwise spirals. This spiralling has never been seen in any other plant in space. The moss experiments fell 64 kilometres to Earth, and were found scattered across a 5-mile area around Bronson, Texas, by retrieval crews during February and March 2004. Most of the samples were crushed, but 11 of the 87 recovered cultures were usable. One of the dishes was linked to a temperature recorder, which shows a spike in the experiment's temperature as Columbia exploded, followed by the daily fluctuations of temperature between night and day. Before returning to Earth, the astronauts had added chemicals that stopped the moss growing, so all its growth is known to have occurred in space alone. After an experiment flown on the Columbia shuttle in 1997 found spiral growth in 2 moss samples, Sack prepared 100 Petri dishes of moss seeds sealed inside aluminium containers for the Columbia's final mission. On Earth, plants can tell which way is up and direct their growth accordingly. In microgravity, they generally grow in random directions. You wouldn't expect to find such a distinctive pattern of growth in microgravity. Common roof moss grows towards light. But in the dark, gravity takes over and the moss grows upwards, as if it were escaping from beneath a layer of soil. Sack believes that removing both light and gravity reveals a more primitive mode of growing. Perhaps spirals are a vestigial growth pattern that became masked when moss evolved to respond to gravity^ref. The moss grows by sending out thin filaments; new growth occurs only at the tip. This means that a single cell at the end of the filament must sense gravity and direct the next cell's growth. We still don't know how plants sense gravity. Biologists believe that gravity moves structures that sit between the cells. These may open or close channels that carry signalling chemicals to stimulate growth in particular areas of the plant. Different plants have evolved their response to gravity separately. A spiral is a very efficient way of spreading over a wide area, so this could have been the moss's original way of growing, ensuring that space was filled without parts of the plant crossing over each other and blocking light from filaments beneath.




The space shuttle Discovery has finally reached the launch pad from which it will blast off once more into space. Discovery was rolled out in a painstaking 11-hour process that lasted into the small hours of Thu 7 April 2005. At 1:20 am local time it was finally locked into position on the launch pad at Kennedy Space Center in Florida, after travelling the 4.2 miles from its assembly hangar. The event marks a milestone on the long road back to orbit for the shuttle fleet. The 3 remaining shuttles have been grounded since 1 February 2003, when Columbia broke apart on re-entry.  Discovery has been fitted with digital cameras on its body and main fuel tank, as well as 88 temperature and impact sensors on each wing to spot any damage during take-off or orbit. NASA's website reports that officials found a small crack in the tank's foam insulation before Discovery was rolled out, but it was deemed too minor to require repair. The shuttle is now awaiting take-off, which is scheduled to happen between 15 May and 3 June. The 12-day trip is the 114th shuttle mission and Discovery's 31st flight. It will involve 7 astronauts, who will test new shuttle-safety equipment and deliver supplies to the International Space Station^ref. NASA has been forced to postpone the launch of the space shuttle Discovery after a routine test revealed a faulty fuel sensor.  The shuttle's seven crew-members, led by commander Eileen Collins, were already strapped into their seats, with just over 2 hours until blast off, when mission control scrubbed the launch. The earliest time Discovery could launch is 1840 GMT on Saturday 16 July 2005, but that may be optimistic. Worryingly, NASA has seen problems with these sensors before, but has been unable to identify the causes. The faulty sensor is 1 of 4 that measure the amount of liquid hydrogen inside the external fuel tank. The test involved sending an electrical signal telling the sensors, which read 'wet' when immersed in fuel, to flip to 'dry' instead. But the faulty sensor continued to read 'wet'. The sensors provide backup protection for the shuttle's engines by shutting them down in the unlikely event of the hydrogen supply running low, due to a leak for example. In a hastily convened press conference a few hours after the launch was scrubbed, mission managers said they had never tested what happened to an engine if the hydrogen dried up, but that it would probably be catastrophic. If the hydrogen runs out, the engines would be fed pure liquid oxygen. The eyes of the world are watching whether the agency is able to send its astronauts into space two and a half years after Columbia broke up on re-entering the Earth's atmosphere. But the shuttle has never flown with a faulty sensor before, and they are certainly not going to start now. A hint of the fuel gauge problem was spotted back in April. To prevent a problem with ice build-up on the tank, Discovery was rolled back into its hanger to have its fuel tank swapped for one with a heater. During tests, engineers also found that 2 of the 4 hydrogen sensors were giving intermittent readings.  To try to fix the problem, some of the electronics on Discovery were swapped with those from Atlantis, another of NASA's shuttles. But further testing showed more problems, so the electronics were swapped again, this time with spares from Endeavour. The actual cause of the problem was never identified. Discovery's external tanks have now been drained of the 2 million litres of liquid oxygen and hydrogen. The investigation into the fault will start with external circuits that connect the shuttle to the fuel tank, but to carry out more tests inside the tank itself, the craft may have to be trekked the 7 kilometres back to its hanger. The current launch window runs until 31 July. If Discovery misses the deadline, it will have to wait until 9 September, when the International Space Station will again be in the right position for docking. Timing this flight has been more difficult than scheduling previous shuttle missions, because the launch must happen during the day so that ground cameras can watch for falling debris, such as the chunk of foam that caused the Columbia accident. Earlier in the day, concerns were raised after a window cover fell off the front of Discovery's cockpit and damaged some of the craft's heat resistant tiles. But the repairs were completed in about an hour. The troublesome sensors may not be so easy to fix.
The space shuttle will not fly again until at least 4 March 2006, NASA confirmed on Aug 18, 2005 : extensive engineering work needs to be done on the external fuel tank to stop insulating foam debris falling off, the agency said. Until this is done, the shuttles will stay grounded. NASA has also changed its game plan for the next shuttle launch. Atlantis was meant to be next, taking to the skies in September 2005. But now Discovery is slated to make the second test flight, months later than planned. This will ensure that Atlantis, which is better equipped to carry up segments of the growing International Space Station, is ready to jump straight into the next available flight slot. The delay on this flight puts further pressure on the station, which is relying on the shuttles to deliver its remaining modules before the shuttle fleet retires in 2010. NASA administrator Mike Griffin would not be drawn on how many more shuttle flights could be launched before that planned retirement date. They're not trying to get a specific number of flights out of the system : instead the goal is simply to complete the space station, and retire the shuttle in an orderly fashion. The shuttle fleet was originally grounded after a chunk of foam tore a hole in the wing of Columbia when it launched on 16 January 2003, causing it to break apart when it re-entered the Earth's atmosphere. The shuttles returned to flight after two years of repair. But despite NASA spending more than $200 million trying to stop the foam from falling off, a similar chunk came loose when Discovery launched on 26 July. The foam did not damage Discovery, and the crew returned safely to Earth 14 days later. But they were lucky. The delay is necessary to truly fix the foam problem : they're starting to understand the mechanism of foam loss, but more work is needed. External tanks that have already been prepared for future flights will now have their foam dissected to check how well the insulating layer is stuck. Gerstenmaier and Griffin both emphasize that it may take several weeks of engineering work before 4 March is officially confirmed as a launch date. The blow to the shuttle programme comes just a day after members of the Return to Flight task group slammed NASA's approach to making the shuttle spaceworthy again. The group oversaw the way NASA carried out the recommendations of the Columbia Accident Investigation Board (CAIB), and presented its final report on 17 August 2005.  Although the majority view of the 26-strong panel was that NASA had done its utmost to fulfil all the recommendations, 7 dissenting voices made a scathing critique of NASA's efforts in an annexe to the report. The group included a former shuttle astronaut and a former chief engineer for the International Space Station. The minority group writes that launch dates were continually pushed back, so that engineers were never sure if they had months or years to tackle the foam problem. If they had known that the return to flight would take more than two years, they may have fundamentally redesigned the tank, rather than trying to make quick fixes. "Too often we heard the lament: 'If only we'd known we were down for 2 years we would have approached this very differently'. A culture of complacency among NASA managers has also persisted, they write: "NASA's leaders and managers must break this cycle of smugness substituting for knowledge. At the end of 2.5 years and $1.5 billion or more, it is not clear what has been accomplished. However, they agree with the group's consensus that the improvements did significantly reduce the risk to the shuttle and its crew, and that the shuttle was not unsafe to fly. Discovery, which landed at Edwards Air Force Base in California on 9 August, is due make the hop back to Florida on 19 August, piggy-backing on a modified jumbo jet. The journey has been delayed by difficulties in fitting an aerodynamic tail to the shuttle, which reduces drag during the flight.
Web resources :
• NASA Shuttle return to flight
• NASA: Human Spaceflight
• NASA's Shuttle programme
• Return to flight task group
• NASA's Return to Flight page
• space tourism / private space travel :
• the $25,000 Orteig prize, which spurred Charles Lindberg's 1927 flight across the Atlantic and which some credit with boosting the commercial aviation business.
• the $10 million Ansari X prize is a cash pot set up by space enthusiasts for the first private manned rocket to carry the weight of 3 people into space twice within 2 weeks, for which more than 20 teams are registered.
• SpaceShipOne was designed by Burt Rutan and his team at Scaled Composites, a company based in Mojave, California, and is backed by Microsoft co-founder and philanthropist Paul Allen : it lifted off from the California desert on 21 June 2004, strapped to the belly of a supporting aeroplane called White Knight. Once the pair reach an altitude of around 15 kilometres, the carrier plane will release the rocket. If everything goes smoothly, SpaceShipOne will shoot up to 100 kilometres, by firing its motor for 80 seconds and then cruising to the top of its trajectory. The pilot, who has not yet been named, will feel zero gravity for 3 minutes while glimpsing the darkness of space, the glimmer of stars and the remote California coastline. After falling back through the atmosphere, the rocket will glide back down to the runway. Buoyed by a successful test flight in May to over 64 kilometres, Rutan's team have invited the public to view this launch and are predicting roads jammed with spectators. SpaceShipOne differs from today's conventional rockets, which fire directly into space like missiles. And unlike the Space Shuttle, which is powered by hydrogen and oxygen, its custom built engine burns a mix of nitrous oxide and rubber, a cocktail that provides less power but is less flammable and therefore safer. If SpaceShipOne reaches 100 kilometres, it will achieve suborbital flight, meaning that it flies out of the atmosphere and grazes space, but does not go fast enough to enter a continuous orbit around the Earth. To reach suborbit, SpaceShipOne has to hit a top speed of about 1 kilometre per second; it would have to multiply that by 8 in order to enter orbit. SpaceShipOne's price-tag of over US$20 million is thought cheap compared to government-financed manned space flight. SpaceShipOne powered into space from the California desert early on Wed Sep 29 morning, completing the first half of bid to win the coveted Ansari X prize. On that trip, a hitch in the steering controls meant that the spacecraft barely scraped over the official 100-kilometre boundary between the Earth's atmosphere and space, reaching nearly 103 kilometres. Rutan's team says that it has since repaired the fault and tweaked the engine. Reports from Wednesday's flight said that the craft had rolled unexpectedly during its ascent, but flight controllers said that it had reached its target height. On 27 Sep entrepreneur Richard Branson announced that his Virgin group, which runs Virgin Atlantic airlines, had agreed to license the SpaceShipOne technology to build a fleet of spacecraft modelled on SpaceShipOne and, with tickets priced at more than US$200,000, to send up the first passengers as early as 2007. To scoop the $10-million trophy for commercial spaceflight, the rocket must repeat the flight, again carrying a pilot and the weight of 2 passengers above 100km, within 2 weeks : the second launch was scheduled for Monday 4 October, when it peaked at over 112 kilometres - the highest of the rocket's three trips into space. It also appeared smoother than last week's qualifying flight, in which the rocket was seen to make numerous rolls. The $10-million prize money was handed over to Burt Rutan, who led the Scaled Composites engineering team responsible for the craft, at a ceremony in St Louis, Illinois, on 6 November. Since then, the Ansari Foundation has announced that an annual X Prize Cup will be awarded for feats of sub-orbital space flight.


• da Vinci Project, based in Toronto, Canada : Wild Fire rocket launched from the world's largest helium balloon over 24 kilometres employs a powerful hybrid engine that burns a mix of nitrous oxide, or laughing gas, and a solid fuel. Wild Fire has got by with around US$350,000 and many volunteer hours
Web resources :
• X Prize Special at Nature
• Scaled Composites
• 'America's Space Prize', worth $50 million, is being offered by Bigelow Aerospace of Las Vegas, Nevada, a company established in 1999 by hotel magnate Robert Bigelow to build an orbiting inflatable space hotel. Bigelow also runs the hotel chain, Budget Suites of America. The prize will be awarded to a craft that can take a crew of at least 5 people to an altitude of 400 kilometres, and complete 2 orbits of Earth. This feat will have to be repeated within 60 days. The craft must be able to dock with Bigelow's space hotel (which he hopes to launch in 2008), and be capable of staying docked in orbit for 6 months. The deadline for these flights is 10 January 2010, allowing very little time for aerospace developers to prepare their entries. Bigelow had hoped to buy Russian Soyuz craft to service his orbiting hotel. But since the crash of the Space Shuttle Columbia on 1 February last year, NASA has relied on Soyuz to deliver supplies to the International Space Station. Bigelow believes that after the space-shuttle fleet is retired, NASA will still need to use the Russian ships as space workhorses. This has upped the going price for a Soyuz, and forced Bigelow Aerospace to look for alternative transport systems. Bigelow Aerospace is also offering hefty contracts for any craft that can begin bringing customers to the space hotel. The rules of the competition do not allow government funding for the projects, and teams from outside the United States are excluded from entering. This may be a response to fears that regulations designed to stop the export of military hardware from the United States could hamper progress in commercializing civilian space flight by restricting trade. The rules of the prize also state that no more than 20% of the craft's hardware must be expendable. Many space shots still rely on huge rocket boosters that are lost during launch, and coming up with reliable alternatives will be a significant hurdle for competitors.
• A US millionaire has booked a holiday with the Russian space agency that should put him in space in October 2005. But businessman, scientist and adventurer Gregory Olsen won't just be taking in the view; he says he plans to perform some experiments during his stay on the International Space Station (ISS). Olsen had originally planned to take his trip of a lifetime in April 2005, but Russian officials postponed it last summer after an undisclosed health problem was discovered. Olsen, who is about 60 years old, resumed training at Russia's Gagarin Cosmonaut Training Centre outside Moscow in May 2005, and has now signed a contract with the Russian agency. The space traveller could join a Soyuz craft that is taking supplies to the ISS as early as October 2005 and would return after 8 days in a different craft. Sources put the price of the trip, arranged through the specialist travel agent Space Adventures, based in Arlington, Virginia, at US$20 million. If successful, Olsen will become the world's third space tourist after fellow American Dennis Tito and South African Mark Shuttleworth. But Olsen prefers another description for himself: at a press conference in 2004 he said he would rather be called a "private researcher", in recognition of the fact that he is "going to do a lot of science up there". Olsen has a doctorate in materials science and started his career as a research scientist before founding 2 successful companies making electronic imaging equipment: EPITAXX and Sensors Unlimited, both based in Princeton. One of his experiments will be to grow semiconducting crystals of the type used in his company's infrared imaging products, which include cameras used for night-vision equipment. Although Olsen was unavailable to comment in more detail on the nature of his experiments, experts speculate one may have something to do with semiconductors made of unusual materials. The most commonly used semiconductor, found in computer chips, is silicon. But not all semiconductors are as easy to work with as silicon. Some other semiconductors are not so easy to grow into crystals and the effect of gravity can be limiting. It could be that Olsen has a semiconductor with certain advantages that is very sensitive to the effects of gravity. Growing crystals of such semiconductors in space could be useful. Olsen will also take one of his company's miniaturized infrared cameras aboard. He will use it for near-infrared astronomy, and to observe crops and the effects of pollution in the atmosphere from above. Infrared astronomy is difficult from the Earth: you don't get a perfect view of the sky because the atmosphere also emits infrared. But he expresses reservations about the true value of Olsen's contribution, pointing out that there are already at least two satellites with dedicated equipment to make infrared observations. It remains unclear what Olsen's experiments will contribute to the world of scientific knowledge, but his mission should certainly add to the burgeoning industry of space tourism. In addition to orbital trips, Space Adventures is developing a programme to take passengers on suborbital flights starting in 2007.
• Big Bang : tiny fluctuations in the density of matter after the Big Bang are definitely reflected in the distribution of galaxies in our Universe, according to 2 research groups. The findings confirm theories of how the Universe grew from being almost uniformly smooth to having dense clusters of stars and galaxies. Theorists calculated in the 1960s that galaxies must have been seeded in places where matter had slightly gathered together immediately after the Big Bang, which is thought to have created the Universe several billion years ago. These fluctuations were seen as ripples in the cosmic background microwave radiation by NASA's Cosmic Background Explorer in 1992, and NASA's Wilkinson Microwave Anisotropy Probe in 2003. But this radiation, which is often described as the afterglow of the Big Bang, originated a mere 400,000 years after the event, long before galaxies formed. 2 sky surveys have now seen evidence of the fluctuations in the separations of galaxies that existed 10 billion years after the Big Bang. This establishes a firm link between primordial instabilities in the Universe and the graininess we see in the cosmos today. The Two-Degree Field Galaxy Redshift Survey (2dFGRS), based at the Anglo-Australian Telescope in New South Wales, Australia, has spent 10 years mapping the distribution of 221,000 galaxies. In a complementary effort, the Sloan Digital Sky Survey (SDSS) at the Apache Point Observatory in Sunspot, New Mexico, has observed 46,000 galaxies in the northern hemisphere over 6 years. The researchers looked at the distance between pairs of galaxies, and found that there was a slight excess of those that were separated by 500 million light years, just as predicted. Seeing the ripples from the microwave background radiation amplified into the pattern of galaxies is evidence for a connection between the 2. The surveys have also provided the most accurate measurement of the mass in the Universe, finding that just 18% of its mass is visible stuff made of atoms and stable subatomic particles. The rest is dark matter, which may consist of more exotic, undiscovered particles that are only detectable through their gravitational influence on the surroundings. The amazing thing about these results is that they are in perfect accord with predictions of our standard cosmological model. This confirms that the shape of the universe must largely be decided by dark energy, the mysterious force that is driving the Universe's expansion at a much greater rate than expected. Preliminary results in 2001 had tentatively suggested that galaxies showed a characteristic distribution, but both surveys now see it very convincingly. Having matching evidence from the two groups is vital. Fundamental questions about the Universe are too important not to have a second opinion. The teams now hope to use the surveys as a yardstick to measure how the Universe's rate of expansion has changed over time. The influence of dark energy seems to have grown significantly over the last few billion years, so working out the separation of galaxies of very different ages could help to pin down exactly how the unidentified force works
• scientists searching for waves of gravitational energy that stretch space and time will soon be seeking the public's help in analysing their data. Researchers at the Laser Interferometer Gravitational Wave Observatory (LIGO) hope to enlist up to 1 million personal computers in their search for sources of the waves, which have long been predicted but never seen. Their distributed-computing scheme, set to launch on Feb 2005, aims to be one of the largest projects of its kind ever created. The software is already in beta testing. Albert Einstein's general theory of relativity lays out the idea that gravity distorts space and time. As a test of his theory, Einstein predicted that waves of gravity would ripple through the cosmos. Some claim such waves have been spotted indirectly, from observations of how paired stars influence each other's orbits, but nobody has seen them firsthand. Since 2000, researchers at LIGO have scanned the sky for tiny shifts of space that would prove Einstein's theory. The project is being built by the California Institute of Technology and the Massachusetts Institute of Technology on 2 sites, one in Livingston, Louisiana and the other in Hanford, Washington. It uses a system of lasers and mirrors that can detect a shift in space as small as the width of an atom. LIGO's best hope for detecting gravity waves is to spot a cosmic source that sends out regular ripples of gravitational energy. A source such as a spinning star made of neutrons would set the detectors ringing like a bell. The problem is that the detectors pick up an enormous number of unwanted vibrations. It's a needle in a haystack problem: 99.99% of the data is noise.  This kind of search is not anywhere near possible with LIGO computing facilities : the data must be analysed at many frequencies, increasing the computer power needed, so the group is enlisting the public's help. Starting in Feb 2004, anyone can download a program that will automatically analyse a small chunk of the group's data on his or her personal computer. The project, known as Einstein@home, will use the computer's idle time to search particular frequencies for a 'ringing' gravity wave source. While it's at work, the programme also displays a screensaver charting the location of the search in the night sky. Einstein@home joins a growing number of distributed-computing projects. The original, SETI@home, launched in 1999 to search for signals from extraterrestrials, has attracted > 5 million users. More recent attempts to model everything from climate change to protein folding have enlisted hundreds of thousands of home computers. Einstein@home will be among the most ambitious of such projects. LIGO is generating data sets so large, and looking for a signal so small, that it will take around a million active users to make a dent. But the more the merrier: the data set is so massive that even all the computers on the planet wouldn't be enough.

Web resources : GEO-600
• Long before the first stars ignited, ghostly blobs of dark matter were forming in our Universe. Dark matter produced just after the Big Bang formed into haloes as heavy as the Earth and as wide as the Solar System. The haloes' gravity would have pulled other matter together, which eventually formed stars and galaxies. These structures, the building blocks of all we see today, started forming only 20 million years after the Big Bang. There are now > 1 quadrillion (10¹⁵) of these haloes in our Galaxy alone, enough for the Earth to pass through 1 every 10,000 years^ref. Astronomers have a good chance of detecting flashes of g rays emitted by the haloes. The evidence for the haloes depends on unproven physics. Dark matter makes up > 80% of the Universe's mass. Although invisible, dark matter betrays its presence by its gravitational pull. For example, without dark matter to hold them together, rotating galaxies would simply fly apart. A leading candidate for dark matter is a particle called the neutralino, which has never been detected, but a branch of particle physics called supersymmetry predicts its existence, as a massive partner to a known particle called the neutrino. Supersymmetry models predict the neutralino's mass and how it can be created. The neutralino is its own antiparticle, so when 2 collide they annihilate each other in a blast of g rays. g rays are constantly being emitted from the dense central regions of the halo, so astronomers should be able to find physical evidence for the ancient congregations of neutralinos. And if you can detect these halos, you can backtrack to work out the precise conditions that generated them. Neutralino collisions would be extremely rare. Nevertheless, the HESS (High Energy Stereoscopic System) telescope in Namibia could pick up the flashes of light in the atmosphere caused when the gamma rays reach Earth. As the g rays enter the Earth's atmosphere they create a shower of photons that sensitive telescopes can observe. NASA's Gamma-ray Large Area Space Telescope, scheduled for launch in 2007, should be able to detect the g rays from space. Back on Earth, the Large Hadron Collider currently under construction at CERN, the European particle-physics laboratory near Geneva, Switzerland, will hunt for supersymmetric particles such as neutralinos when it opens in 2007.

Web resources : Theoretical Physics at the University of Zurich
• the Universe consisted of a perfect liquid in its first moments, according to results from an atom-smashing experiment. Scientists at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory on Long Island, New York, have spent 5 years searching for the quark-gluon plasma that is thought to have filled our Universe in the first microseconds of its existence. Most of them are now convinced they have found it. But, strangely, it seems to be a liquid rather than the expected hot gas. Quarks are the building blocks of protons and neutrons, and gluons carry the strong force that binds them together. It is thought that these particles took some moments to condense into ordinary matter after the intense heat of the Big Bang. To recreate this soup of unbound particles, the RHIC accelerates charged gold atoms close to the speed of light before smashing them together. Previous experiments have shown that these collisions create something the size of an atomic nucleus that reaches 2 trillion °C, about 150,000 times hotter than the centre of the Sun. This stuff was last seen in the Universe 13 billion years ago. Now experiments have revealed that this hot blob is a liquid, which lives for just 10-23 seconds. The surprising thing is that the interaction between the quarks and gluons is much stronger than people expected. The strength of this binding keeps the mixture liquefied despite its incredible temperature. The researchers worked out the liquid's structure by tracking the particles that spray out as the droplet falls apart and quarks team up to form normal matter. The resulting liquid is almost 'perfect': it has a very low viscosity and is so uniform that it looks the same from any angle. This may help to explain why the deepest parts of the Universe seem similar wherever astronomers look. If the primordial liquid had been as viscous as honey, the Universe could have turned out much more lumpy. The researchers now hope to measure the heat capacity, viscosity and even the speed of sound in the quark liquid. But the RHIC has been hit by cuts in the recent US budget, forcing it to reduce its operating time from 30 to 12 weeks in 2006. Further investigations will inevitably take years to complete^ref.
• g-ray bursts are sudden flashes of radiation in the sky, and their fleeting nature has made it tricky for astronomers to work out what causes them. Although some bursts last for minutes, some are visible for just a few milliseconds. Astronomers are now fairly sure that longer g-ray busts come from the collapse of massive stars. But the shorter bursts are more mysterious, and may be generated when 2 neutron stars collide. NASA's Swift satellite, which will track the most powerful explosions in the Universe, launched successfully on Saturday 20 November 2004, at 1716 GMT. Swift is an apt name for the satellite, because it can detect these short bursts and quickly turn its X-ray sensors to soak up the afterglow, providing scientists with clues about their origin : in a few minutes, they release as much energy as our Sun releases over the whole of its 10-billion-year lifetime. They are the biggest bangs since the big one. The scientists hope that Swift will detect about 3 g-ray bursts every week. The bursts were first seen in 1969 by a satellite used to monitor the Nuclear Test Ban Treaty, but it was not until the Italian-Dutch orbiting telescope BeppoSAX analysed the X-ray afterglow of a g-ray burst in 1997 that astronomers realized the explosions were coming from distant galaxies. In fact, many of the bursts seem to date from a time when the Universe was < 1 billion years old, allowing scientists to see further back into the early history of the cosmos than ever before. Swift will study these g-ray bursts in 3 different stages. The Burst Alert Telescope will be the first to spot the tell-tale rays, locking on to the signal and swivelling the satellite into the optimum observing position in as little as 20 seconds. Just 90 seconds after the burst, an X-ray telescope studies its afterglow, allowing Swift to pinpoint the source with greater accuracy. A third telescope then looks at the source in the ultraviolet and optical part of the electromagnetic spectrum, pinning down the position of the burst with even more precision. Within 5 minutes, the satellite transmits all this information back to Earth, where it is distributed to astronomers around the world by e-mail and text message. It will also trigger more powerful ground-based robotic telescopes to watch the optical afterglow that persists for many minutes after the initial burst. The launch had been delayed several times because of a problem with the craft's communications equipment. Engineers had found faults in a receiver that is responsible for picking up signals from mission control to make the rocket self-destruct if it veers off course. They fixed the problem on 19 November. Swift is now orbiting about 600 km above the Earth. After calibrating the instruments on the 5.5 m-long craft, it should be fully operational by the end of March 2005. Intense flashes of g-rays in far-off galaxies might be produced by a bizarre kind of star, consisting of phenomenally dense material in which the particles that make up atomic nuclei have fallen apart. 2 astrophysicists have proposed that g-ray bursts, whose origins have foxed astronomers for decades, might be the signatures of elusive 'quark stars'^ref. The quark-star hypothesis might explain some puzzling observations made by the Burst and Transient Source Experiment (BATSE) on NASA's Compton Gamma-Ray Observatory, which was launched in 1991. Lazzati noticed that several of the g-ray bursts seemed to be preceded, a few seconds or minutes earlier, by much weaker pulses of g-rays^ref. Astronomers generally believe that g-ray bursts are produced by supernovae: stars that have run low on fuel and do not emit enough energy to prevent them from collapsing under their own gravity. The collapse heats up the star and generates a 'rebound', in which the star's outer layers get blown off in a massive explosion, while the inner core collapses further into a superdense object called a neutron star. These stars are made entirely of neutrons, the electrically neutral particles in atomic nuclei. They measure just a few miles across and are so dense that a teaspoonful of neutron-star matter weighs about a billion tonnes. The g-ray bursts seem to be associated with a certain type of supernovae, called type Ic, in which the parent stars have already become quite compact. The g-ray flashes are produced as the supernovae throw out jets of material that move at almost the speed of light. But although only a few have so far been spotted, not all type-Ic supernovae generate these bursts. Why should the supernovae differ? The difference could depend on whether the explosion produces a neutron star or whether this superdense core contracts even more, bursting open the neutrons themselves to create a soup of quarks, the particles from which they are made. The surface of a quark star would act as a kind of filter that stops particles called baryons escaping from the star. Baryons are the components of nuclei: protons and neutrons. The surface of a quark star is a one-way street for baryons. This 'membrane' could account for the ultrafast jets squirted out of the supernova, because it would be permeable only to non-baryon particles, such as photons and neutrinos, which move at or very close to the speed of light, and would bar the ponderous baryons that slow the jets down. Crucially the transition from a neutron star to a quark star should take a few minutes. That is precisely the kind of delay between the weak precursor flashes reported by Lazzati, which would appear as the neutron star is formed, and the main g-ray bursts, which would come slightly later as it turns into a quark star. Paczyski says that the first step in testing their idea is to establish whether there are truly two classes of type Ic supernovae: one with bursts and one without. So far, there are only 4 observations from which to judge. NASA's Swift satellite spotted an energy burst at 4:00 GMT on 9 May 2005. The event, named GRB050509b, threw out a very short blast of g-rays : 90% of the event's total energy was released in just 30 ms. The blast is thought to come from 2 neutron stars colliding in a galaxy about 3 billion light years away. All of the evidence we have so far points towards this being a neutron star merger. Astronomers think the neutron-star pair originally formed when 2 orbiting stars exploded in supernovae. The dense remnants of these stars twirled around each other in ever-decreasing circles until they eventually collided and formed a black hole. Astronomers think there are several sources of g-ray bursts in the Universe. Blasts that last more than a few seconds are thought to come from the death of supermassive stars as they collapse in a violent supernova explosion. These are quite well understood, simply because the length of the bursts makes them easier to study. But short g-ray bursts have been very mysterious. Some astronomers argue that they are generated when highly magnetic neutron stars, called magnetars, throw out plumes of material. Swift's observation goes against this theory. GRB050509b is at least 10 times farther away than the most distant magnetar eruptions that Swift would be able to spy. It is more likely to be a neutron star collision, because that is a much brighter source. From simulations of neutron-star mergers, the timescales of the predicted g-ray burst match up pretty well with these observations. Swift was carefully designed to catch short bursts of g-rays and swing around fast enough to record the aftermath of whatever caused them. Just 56 seconds after detecting this burst, Swift got into position to look for the afterglow of X-rays and visible light. It then sent out e-mail alerts to astronomers around the world, who used ground-based telescopes to look at the area. No one has spotted anything so far, but this may be because the distant glow is too faint. This isn't the first microsecond burst that Swift has seen. It spotted one back in February 2005, but couldn't swing into place to observe its source because the Sun was in the way and would have blinded its sensors. This is the first one we've been able to follow up on. Spotting similar short g-ray bursts in the future will help astronomers to work out how common twinned neutron stars are throughout the Universe, and how many black holes neutron-star collisions account for. There are only 4 pairs of neutron stars known in our Galaxy.

The explosion of a star in our cosmic neighbourhood may not sound like good news for life on Earth. But a team of US researchers says that just such a catastrophe could have showered our planet with fertilizer that helped plants to colonize the land about 440 million years ago^ref. Scientists have speculated for at least a decade that g-ray bursts could have caused some of the mass extinctions in Earth's distant past. These explosions are thought to be either the by-product of a supernova, when an old star explodes, or the result of a collision between ultradense bodies called neutron stars. They release torrents of high-energy radiation (g-rays) focused into twin 'lighthouse' beams. All the bursts seen so far have occurred in distant galaxies, but in the past billion years at least one is likely to have occurred close enough to Earth to have had some dramatic effects on our planet. A nearby burst would have destroyed much of the ozone layer that protects the Earth's surface from the Sun's harmful ultraviolet rays, so that many species would have been fried. To make matters worse, the -rays would convert nitrogen and oxygen in the atmosphere into nitrogen dioxide, a brown, toxic gas that is released today in vehicle exhaust, causing urban smog. A 'g-ray burst smog' would have cast a shadow over the planet and could even have triggered an ice age. In 2003, Adrian Melott of the University of Kansas claimed that this might have happened at the end of the Ordovician period, about 440 million years ago. The geological record shows evidence at this point of mass extinctions and global cooling^ref. Melott has now collaborated with astrophysicists and atmospheric scientists to develop a computer model of the effects that a nearby g-ray burst might have. The initial results, which they reported earlier this year, looked like an unrelenting litany of disaster^ref. Ozone depletions of about 35% globally (and much more in some spots), tripled intensity of ultraviolet light, widespread DNA damage to surface organisms, and massive formation of nitrogen oxides and consequent acid rain. It all looked very gloomy. But the researchers have now delved into another side-effect. Nitric acid produced from nitrogen oxides might indeed shower the Earth with corrosive rain, but this would subsequently enrich the land in nitrate, which is an essential nutrient for plants. Today, farmers add nitrate to their soil in fertilizers. The geological record shows that it was precisely in the late Ordovician period that plants began to spread extensively over the land, in the crucial first step of colonization by life. So if a g-ray burst did cause widespread extinctions, it may also have boosted plants' growth. There was very little life on land at the end of the Ordovician, essentially just algae : plant life began to really take hold after this period, and we think that the nitrate deposited after a -ray burst could have aided this transition. Nitrate is always a limiting factor for plant growth, and would have been much more so then, before there were nitrogen-fixing plants on land. The 3-5 years of extra nitrate that we predict could have boosted plants trying to get a foothold on land.
Astronomers have spotted a signature of neutrinos created just seconds after the Big Bang. The find supports current models of the origins of our Universe, and may provide a glimpse of its birth. The fundamental particles called neutrinos are difficult to study, because they interact so weakly with normal matter - trillions whizz straight through your body every second. But the signature of primordial neutrinos is written in the cosmic microwave background (CMB). These microwaves are the remnants of light that shone 300,000 years after the Big Bang, when light was first free to move in a straight line without being blocked by the soupy material of the early Universe. Researchers have found that the CMB is slightly uneven, reflecting the lumpy distribution of matter in the early Universe. Wayne Hu, a cosmologist from the University of Chicago, proposed that neutrinos should affect these ripples in the CMB^ref. That is what Trotta and Melchiorri have found^ref. During the Big Bang, matter became patchily distributed. This was a result of matter's graininess on a small scale: subatomic particles either exist in a space or they do not, making the distribution of matter unpredictably lumpy. As the Universe grew, its lumps expanded too, spreading matter unevenly about the cosmos. The CMB, for example, contains ripples separated by about one degree - the same size as a full Moon seen from Earth. Trotta and Melchiorri worked on the assumption that fast-moving, energetic neutrinos in the early Universe changed the local gravity enough to smooth out some of the ripples in the CMB. The neutrinos' influence would have been minute, but potentially visible. When they looked at the CMB on a scale of about a hundredth to a thousandth of a degree, they found less variation than expected. This fits with the prediction that neutrinos have a smoothing effect. The fact that we can see this in the WMAP data was a big surprise. The find could help astrophysicists peer further back in time. The earliest we can see at the moment is to 300,000 years after the Big Bang. But neutrinos would have shaped the CMB from a few seconds after the Universe's birth. Learning about neutrinos in the early Universe and their interaction with the CMB should teach researchers about the other particles of that time. Such particles might, for example, stop neutrinos from smoothing out the CMB. The observations aren't definitive yet. It's not quite strong enough to call it a detection, but it goes in the right direction : the next set of data on the CMB, expected this year, could provide a firmer answer. In the meantime, it's reassuring that the results are consistent with theoretical predictions
Using a satellite and a global network of telescopes, astronomers have glimpsed the most distant cosmic explosion ever seen. The explosion, known as a g-ray burst, probably came from a star that died when the Universe was in its infancy. The light from the burst could give researchers insight into the first stars and the ways in which the cosmos has changed over time. g-ray bursts occur, most astronomers believe, during the death throes of giant stars. When stars die, they sometimes explode violently in a process known as a supernova. During the course of the explosion, a star can eject a plume of particles at near light speeds. These particles release an enormous amount of energy in the form of superfast g rays. The g-ray bursts are so intense that they can outshine entire galaxies. This event is pointing the way to the absolute first stars that ever formed. The challenge for astronomers is that most gamma-ray bursts last only a few seconds or minutes before fading away. To help locate them quickly, NASA launched the aptly named Swift satellite, a space-based g-ray telescope that locates a burst within seconds and e-mails its coordinates to nearly 1,000 astronomers around the world. The researchers race to direct their telescopes to the point in the sky where the burst was first spotted, and study its afterglow, which can last for hours or days. The light from this latest burst, which was spotted on 4 September 2005, came from a star that exploded when the Universe was a mere 900 million years old. That's about one-fifteenth of its present age. Astronomers watched the burst fade for several days, using telescopes in Hawaii, Chile, Colorado and other locations around the world. The burst provided a rare glimpse back through space and time. The light from the burst travelled through the clouds of dust that lie between the dying star and Earth, illuminating a narrow beam of the otherwise dark Universe. A Japanese group in Hawaii has gathered data that could help to show exactly what the early Universe looked like. The burst is also important because it happened at a time when the Universe was hugely different from its present state. If we can spot an explosion this old, we might eventually be able to peer even further back in time. This event is pointing the way to the absolute first stars that ever formed, before there were galaxies at all.
Web resources :
Gamma-ray burst map
• Swift at Leicester University
• Swift at the Italian Space Agency
• NASA's Goddard Space Flight Center in Maryland
• Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts
• dark galaxies : a galaxy that is made almost entirely of dark matter has been discovered. It's the first galaxy found to have no stars at all, but it fits well with predictions made by astrophysicists about where the Universe's missing mass should be. Dark matter betrays its presence by its gravitational pull: without dark matter to hold them together, rapidly rotating galaxies would simply fly apart. Scientists estimate that dark matter must be 5 times more abundant than normal matter in our Universe. It is likely to be made of relatively large subatomic particles that rarely interact with their surroundings, although these particles have never been identified. In fact, > 90% of our particular Galaxy's mass seems to be dark matter. The normal matter was pulled into stars, planets and dust clouds, but this doesn't seem to have happened in the dark galaxy. What's bizarre is that the galaxy hasn't converted any gas into stars at all. The dark galaxy, named VIRGOHI21, is in the Virgo cluster, a large group of galaxies about 50 million light years away. It has roughly 10% of the mass of our own Galaxy, the Milky Way, but it's not uncommonly small^ref. The team's first clue came from the behaviour of the neutral hydrogen atoms that shroud this dark region of space. The researchers detected the characteristic radio-frequency signature of these atoms using the Lovell Telescope at the Jodrell Bank Observatory near Manchester, UK. They found that the hydrogen was swirling in exactly the same way as it would swirl around a normal, brightly lit galaxy. At first, they assumed that they were simply looking at a dim, dwarf galaxy. But by watching how the hydrogen moved, the researchers were able to calculate that the mass of the galaxy is relatively large. However, normal matter packed that close should have ignited some stars. If it were an ordinary galaxy, then it should be quite bright and would be visible with a good amateur telescope. He and his colleagues used the powerful Isaac Newton Telescope on La Palma in Spain's Canary Islands, to look for any scraps of visible light from the area; they found nothing. The most likely explanation is that the galaxy is made of dark matter. The inability to find dark galaxies has been a thorn in the side of theories about how dark matter shapes our Universe, which predict that there should be even more dark galaxies than visible ones. Scientists have also speculated that haloes of dark matter might be the gravitational seeds of galaxies, attracting enough normal matter to form stars. The team now plans to use radio telescopes to hunt for more dark galaxies
• magnetars are extremely dense, small stars with magnetic fields at least a thousand trillion times stronger than the Earth's. They are a type of neutron star, the compact remnant of a collapsed sun.
• a cataclysmic 'starquake' is thought to have caused a flare of radiation that ripped past the Earth on 27 December 2004, battering instruments on satellites and lighting up our atmosphere. This is the biggest blast of g and X-rays they have ever observed in our corner of the Universe. They believe the flare came from a bizarre object just 20 km wide on the other side of the Galaxy that released more energy in 0.1 s second than the Sun emits in 100,000 years. Data from satellites and ground-based telescopes have pinpointed the origin of the burst as SGR 1806-20, a 'magnetar' around 50,000 light-years away in the constellation of Sagittarius. The flare may have been caused by a quake on the surface of SGR 1806-20. The quake would have disturbed the star's magnetic field, creating an explosion that was the brightest ever detected beyond our Solar System. It is possible that similar flares have been misinterpreted in the past. Analogous g ray bursts have been detected, but they were assumed to come from very distant objects beyond our galaxy. Fortunately for life on Earth, the nearest known magnetar is about 13,000 light years away - too far for any future burst to damage the planet. The radiation burst from a closer explosion could, for example, wipe out the ozone layer
• a source of ultra-high-energy cosmic rays has been identified for the first time. The extremely energetic particles, racing at almost the speed of light, have been traced back to a pair of colliding galaxy clusters. Cosmic rays are fast-moving particles that constantly bombard the Earth. Some come from the Sun, whereas higher-energy rays are accelerated around the remnants of supernovae. But ultra-high-energy cosmic rays are at least a thousand times more energetic still, and extremely rare. Only one particle is expected to hit each km² of Earth every century. Physicists already know that these particles are almost certainly protons whose energies are measured in exaelectronvolts (10¹⁸ eV) - the amount of energy that an electron acquires when it is accelerated by a billion billion volts. Each proton has a kinetic energy similar to that of a flying golfball, and travels at just one part in 10²² slower than the speed of light. 5 of these particles all came to Earth from a pair of galactic clusters that are crashing together roughly 450 million light years away. Only about 100 of these ultra-high-energy cosmic rays have been detected on Earth in the past decade, and until now all of them seemed to come from different parts of the sky. They travel so fast that magnetic fields in space can barely alter their paths. This means that the particles travel in a virtually straight line to Earth, allowing to plot their paths and work out where they came from. Data came from 2 separate detectors. The High Resolution Fly's Eye fluorescence detector in Dugway, Utah, searches Earth's atmosphere for streaks of light generated when the particles hit. The impacts make the atmosphere fluoresce in a line, and that line points directly at the source. The impacts also start a cascade of secondary reactions in the air, generating millions more particles that shower Earth's surface. The Akeno Giant Air Shower Array (AGASA) in Asao, Japan, has particle detectors covering an area of 100 km². If all the detectors fire at the same time, this indicates a massive event that could only have been triggered by the arrival of an ultra-high-energy cosmic ray. The 5 events that Farrar tracked were spotted between 1993 and 2003. The difference in their arrival time is due to the very slightly different paths they took to reach Earth even the tiniest deviation from a straight line can make a decade's difference over such huge distances. The paths all point to the merging galaxy clusters, a conclusion supported by observations from the Sloan Digital Sky Survey (SDSS), run from the Apache Point Observatory in New Mexico, which show that there is a clear line of sight between Earth and the clusters. The clusters are extremely rich in stars and have powerful magnetic fields that become warped when they collide. It's possible that the turbulent magnetic fields accelerate charged particles such as protons in tight spirals before flinging them towards us. Some physicists have speculated that such energetic particles could only come from the decay of exotic, heavy subatomic particles formed immediately after the Big Bang. But seeing 5 high-energy rays from the same point rules that out, because the chance of finding that many exotic decays along the same line of sight is minuscule
• telescopes :
• ground-based telescopes are usually plagued by the Earth's atmosphere, which bends starlight back and forth as the beams pass through pockets of air with different densities. The effect is similar to the apparent shimmering of a desert, caused by looking through hot air rising from the scorched sand. The calm air above part of the Antarctic makes it the best place on Earth for astronomy. Dome C is the best ground-based site to develop a new astronomical observatory. Even at high-altitude sites elsewhere on Earth, stars seem to jitter in the sky, moving by about 140 millionths of a degree. But over Dome C, the jitter was as low as 19 millionths of a degree, by far the best value ever reported. in order to compare to an optical or infrared telescope built at Dome C, a telescope built at one of the next best sites around the world would have to be two or three times as large. A Dome C telescope could even work on projects that would otherwise require a space mission, they add, and could potentially assist in the hunt for Earth-like planets beyond our solar system. Antarctica was already known to be an attractive location for a telescope because it is so far away from the interference of urban light, heat and smog, and it is also one of the least cloudy places on Earth. Telescopes have been built at increasingly high altitude to reduce the distance the starlight must travel through our turbulent atmosphere. Some telescopes are fitted with hundreds of tiny motors, which move the telescope's mirror to compensate for the jittering. But 'adaptive optics' can only reduce, and not eliminate the effect. Any proposal would require a rigorous impact assessment as in Antarctica we have the most stringent environmental protocols in the world. Anyway there is no wildlife in that part of the Antarctica to disturb, whereas a telescope built in a remote part of Chile, for example, would have a much greater effect on the environment^ref.

space telescopes : Hubble avoids the jittering problem altogether, because it orbits above our atmosphere. Hubble has provided astronomers with some of our best views of the cosmos, spotting planets around distant stars and revealing what the Universe looked like in its earliest years. Hubble has been photographing the Universe for 14 years and was designed to be serviced regularly. But as its batteries run down and its stabilizing gyroscopes fail, Hubble will lose the ability to focus on a fixed point. NASA expects that this may happen sometime in 2007. 4 successful overhauls between 1993 and 2002 were due to be followed by a fifth and final upgrade to the telescope's batteries and gyroscopes, before the Columbia shuttle crash on 1 February 2003 grounded NASA's remaining shuttles. The ailing Hubble Space Telescope should be rescued by humans rather than robots as early as possible after the shuttle is deemed safe to fly. Without prompt action, Hubble could degrade to the point where repair would be impossible, and may even be unsafe to take out of orbit. NASA expects it to take > 3 years to develop a robot mission, and the committee says that this might be too late to save Hubble anyway. It also argues that the risks that a servicing mission pose to a shuttle crew are little different from those involved in building the International Space Station. NASA plans 28 shuttle flights to complete the station by 2010. Space consultants Aerospace Corporation delivered a similar assessment report, commissioned by the space agency, earlier this week. It too found that a robotic repair mission would be more expensive and riskier than NASA had originally anticipated. The panel believes that astronauts would be better than a robot at dealing with unforeseen repairs, something that has been necessary on three of the four previous servicing missions. With proper attention, Hubble could continue operating well into the next decade. US Officials revealed on Friday 21 Jan 2005 that NASA's budget for 2006 contains no cash to save the ageing telescope. Instead, it earmarks funds to decommission the instrument. President George W. Bush will present the budget proposal on 7 February, and the US Congress will then consider it. The telescope could yet win a reprieve. Congress could insist on boosting NASA's budget to include the costs of a servicing mission, as they did in 2004. And NASA has enough flexibility in how it spends its US$16.2 billion budget for 2005 to devote some resources to a rescue mission. NASA spokeswoman Dolores Beasley said that the agency would make no official comment on the forthcoming budget until 7 February. Astronomers insist that a repaired Hubble could deliver valuable science well into the next decade. Although ground-based telescopes can now see further and more clearly into the Universe than ever before, many astronomers still rely on Hubble to glimpse the most distant stars. Hubble has been orbiting the Earth since April 1990, photographing distant stars formed in the earliest stages of the Universe. But 2 of the 6 gyroscopes that stabilize the telescope no longer work, and as more fail Hubble will lose its ability to focus on a fixed point. Its batteries also need replacing before they run down, which is expected to happen in 2007 or 2008. The debate on how to repair Hubble has lasted for > 1 year. On 8 December 2004, an influential committee of the US National Academies' National Research Council recommended that NASA launch a manned rescue mission to service Hubble as soon as possible. But outgoing NASA administrator Sean O'Keefe has always rejected a manned mission as too risky, favouring a robotic saviour instead. Each option would cost at least US$1 billion. Now it seems that Hubble's last visitor may be charged with guiding it into an orbit that brings the telescope crashing safely into the Pacific Ocean. The budget leaks, widely reported in the US media, may be an attempt by Hubble supporters in the government or NASA to put the debate firmly back in the public arena. The fuss could put pressure on politicians to save the popular mission. It's thought that President Bush wants to invest in manned space missions instead of repairing the Hubble. Hubble has been serviced by the space shuttle 4 times in the past 15 years. A fifth mission was scrapped after the shuttle Columbia crashed on 1 February 2003, putting NASA's fleet out of commission while it made safety checks. The Discovery shuttle is expected to fly in May 2005. The shuttles will devote much of their time to completing the International Space Station, but a lot of people feel that's a white elephant. The case for spending billions of dollars refurbishing the shuttle would be much stronger if it was going to be used to save Hubble. The Hubble Space Telescope will be scrapped, according to NASA officials who presented the agency's budget for 2006 on 7 February 2005. No money has been set aside for a vital servicing mission, which would replace the telescope's ageing batteries and gyros, but would cost hundreds of millions of dollars. Instead, NASA has given Hubble just US$93 million, with the lion's share earmarked for nudging it out of orbit. NASA engineers are expected to deliver a report in March on how to retrieve the telescope safely. NASA administrator Sean O'Keefe says that the budget reflects President George W. Bush's commitment to manned space exploration missions, which has shifted the agency's focus towards the Moon and Mars. Hubble's supporters are dismayed by the decision. Barbara Mikulski, Democrat senator for Maryland, will fight in the Senate this year to fund a servicing mission to Hubble by 2008. But time is running out for the telescope's supporters. Congress will have to make a decision about Hubble very soon, probably no later than the end of March. A committee of the US National Academies' National Research Council recommended on 8 December 2004 that NASA launch a manned rescue mission to Hubble as soon as possible, ruling out a robotic mission as unworkable. But outgoing NASA administrator Sean O'Keefe has always argued that the tighter safety regulations proposed by the Columbia Accident Investigation Board make a manned servicing mission too risky. NASA software engineers have developed a strategy to keep Hubble focused on the stars for a little longer. This means that 2 of the telescope's 4 remaining gyros, which keep it pointing in the right direction, could be kept as a spares. This might buy Hubble an extra year of life. NASA's purse fared better than those of many other government departments, including energy and basic defence research. The agency's $16.5-billion request was 2.4% higher than last year's final allowance. The largest portion of funding ($4.5 billion) goes to the shuttle, which is expected to return to flight in May or June 2005. The International Space Station, expected to be completed in 2010, will receive $1.9 billion. NASA hopes that the station can be used for more research on the health effects of arduous manned missions. The budget also grants $372 million (a 19% increase) to the James Webb Space Telescope, which is seen by many as Hubble's successor and is expected to launch in August 2011. But the Jupiter Icy Moons Orbiter, a craft that would have relied on nuclear propulsion, has effectively been cancelled. NASA officials now say that the orbiter is just too ambitious, and will not be realized by the proposed 2015 launch date. O'Keefe has been plagued by the quandary over Hubble, and formally resigned from NASA on 13 December 2004. He now expects to leave the agency within days; he will begin his job as chancellor of Louisiana State University, Baton Rouge, on 21 February. April 2005 marks 15 years since the Hubble Space Telescope, hailed by some commentators as the most successful astronomy mission ever, was placed in orbit. Since 25 April 1990, it has snapped 750,000 images, sending 120 gigabytes of data back to Earth each week. But now the end may well be nigh for the ailing telescope. Perhaps Hubble's most impressive achievement is to have peered into the farthest recesses of the Universe, allowing cosmologists the chance to witness the first stars in the act of formation. Images called the Hubble Ultra Deep Fields , taken using lengthy exposures of around 1 million seconds, capture light from so far away - which has travelled for so long to reach us - that the pictures show astronomers what was happening almost as far back as the Big Bang. In recent years, Hubble has also taken ultraviolet images of Saturn's striking aurorae , captured high-speed galactic collisions , and provided hundreds of posters for physics students' bedroom walls. Hubble takes images right across the visible spectrum and into the infrared and ultraviolet wavelengths on either side. The final images presented to the public are likely to have been run through a statistical computer package to iron out background blur or unwanted features, and to sharpen up the subject of the image. The photographs will also probably have had their colour, contrast or brightness tweaked. And for infrared or ultraviolet images, the frequencies of the final image will have been shifted to make them visible. Much of this processing, however, is exactly what astronomers would do when preparing the images for their own use, so they are more than just pretty pictures. It looked to be all over for Hubble when NASA announced its 2006 budget in February 2005. The plan allocated just $93 million to the telescope, most of which was earmarked for getting it safely out of orbit, leaving little for crucial maintenance. Without such repairs, Hubble's batteries are due to run out in 2007 or 2008. The hiatus in shuttle flights after the Columbia disaster has also prevented crews from getting into space to fix the telescope. But Hubble may have been handed a lifeline in the shape of new NASA chief Michael Griffin. He has pledged to revisit the idea of a manned servicing mission, which would cost an estimated $1 billion. He has ruled out the idea of a robotic mission as impractical. If the decision is taken to rescue it, astronauts will travel to Hubble to replace its battery pack, which pumps out the equivalent of 20 car batteries, and its ageing stabilizing gyros. Without such a mission, a robot is likely to be sent up to pull the schoolbus-sized telescope out of orbit and guide it to a safe splashdown in the ocean. Hubble is part of NASA's Great Observatories Program, a four-strong team of space telescopes designed to span a wide range of different wavelengths. Two other space observatories will likely out-live Hubble: the Spitzer Space Telescope, which takes infrared images, and the Chandra X-ray Observatory. The final member, the Compton Gamma-Ray Observatory, was decommissioned in 2000 after 9 years in orbit. Hubble's successor will be the James Webb Space Telescope - also designed to peer into the early Universe. Scheduled for launch in August 2011, this instrument will sit 1.5 million km from Earth, and look at light in the infrared. From its vantage point in space, Hubble has given astronomers views of the Universe they could not have got from under Earth's blanket of magnetic fields and radiation. Launched at a cost of $1.5 billion, it has now had three servicing missions, only one of which - a trip to fix a focusing defect in one of its mirrors - was unplanned. The telescope was initially seen as having a potential working lifetime of 20 years. But given its prolific output, each image has averaged a cost of just a few dollars. Even if the telescope's champions fail in their campaign to save it, Hubble can retire with the satisfaction of a job well done^ref.
• a few precious spots on the Moon may be bathed in permanent sunlight, according to planetary scientists. These bright, temperate areas might make ideal sites for a lunar base. Researchers have long suspected that mountains and crater rims at the Moon's poles might bask in constant sunshine. But without a detailed analysis of the lunar landscape, this has been a tough theory to test. A team led by Ben Bussey of the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, analysed pictures taken by the spacecraft Clementine, which circled the Moon in 1994. The researchers overlaid a series of images of the Moon's north pole taken over a lunar day - which lasts about 28 Earth days - and searched for regions that are constantly illuminated. A handful of spots on the rim of the Peary crater were lit for the entire lunar day and may be sun-baked all year round. A person standing there would see the Sun hover near the horizon but never sink below it. "It would be very surreal and very beautiful.Nowhere on Earth enjoys all-year sunlight, because the planet's axis is tilted about 23º relative to the plane of its orbit around the Sun. Each of the poles basks in 24-hour sunlight when it is leaning towards the Sun in summer - but it dwells in permanent darkness when tilting away from it in winter. The Moon, by contrast, sits more upright, being tilted at just 1.5º relative to the Earth's path around the Sun. This led scientists to believe that certain lunar peaks might remain in sunshine all year round. Bussey's team carried out their analysis of the north pole during the lunar summer, when it was tilted towards the Sun. To see whether the sites remain lit during the lunar winter, they will need snapshots of the pole during that time, or a more accurate map of the area's topography. This should be achieved by one of a series of planned lunar missions such as Chandrayaan-1, which is scheduled for launch in 2007. The perpetually sunlit spots proposed by Bussey's team could make perfect sites for building a manned lunar base. For one thing, they would benefit from bountiful solar energy. What's more, climate calculations suggest that they would hover at a relatively balmy -50 ºC. This is far more hospitable for man and machine than the Moon's equatorial regions, in which temperatures swing wildly from -180 ºC to 100 ºC. Bussey's analysis is particularly timely because of the Bush administration's goal of sending astronauts back to the Moon and on to Mars : it gives us a solid idea about one aspect of where missions should go. The lunar poles are already enticing because of suggestions that they might hold pockets of ice, and hence a supply of water. Earlier analyses by Bussey's team revealed dips in the polar landscape, such as crater bottoms, that are in permanent shadow and might harbour ice. They also analysed the lunar south pole for permanently sunlit spots - but came up empty-handed.


Web resources :
• Australian Antarctic Division
• British Antarctic Survey
• Dome C Project
• Centre for Astronomical Adaptive Optics (CAAO)
• Space Telescope Science Institute
• comets : astronomers think that many come from the Oort cloud, a field of billions of icy objects that lies up to 100,000 times farther away from the Sun than the Earth does and marks the outer boundary of our Solar System. The icy objects are sometimes driven towards the Sun by gravitational tides generated by the shifting masses of stars in our Galaxy. When this happens they become comets, orbiting the Sun every 20 to 200 years on paths that lie at an angle to the planets' orbits. Given the size of the Oort cloud, astronomers have calculated that there should be about 3,000 comets in these orbits, 400 times more than are actually observed. These things will just come out of the dark and hit you with no warning. The common explanation for this discrepancy is that the comets quickly disintegrate into smaller lumps after just 1 or 2 orbits. But a new mathematical model now suggests that, if this were true, the debris should cause many more major meteorite showers on Earth than we see, perhaps up to 30 every year. Sedna, the most distant body identified in our Solar System, could have an orbiting twin that is dark, fluffy and made of tarry carbon compounds : as Sedna may be a member of the Oort cloud, other members of the cloud could be equally dark. Once ejected, the tarry comets would simply suck up visible light, remaining cloaked in darkness. In June 2004 NASA's Stardust probe, which is bringing back samples of dust from the comet Wild 2, reported finding lots of tarry carbon compounds spraying from the comet^ref. The dark comets would present a major challenge to astronomers searching the skies for objects that might collide with the Earth. However, although they reflect almost no visible light, the dark comets should give out a tiny glow of heat, visible as infrared radiation. The infrared Spitzer Space Telescope, which has been operating from Earth orbit for just over a year, has not seen any dark comets. But this could be because it focuses on very small, distant parts of the sky. But if these objects existed in the numbers proposed by Napier, either Spitzer or near-Earth object surveys such as Spacewatch, based at the University of Arizona in Tucson, would have picked them up by now. A new space telescope might provide the answer. Earlier this month, NASA announced that it would launch an orbiting infrared telescope called the Wide-field Infrared Survey Explorer (WISE) in 2008, which will map much wider areas of the sky. Given enough time, it should be able to detect the dark comets.

What's the best way to see inside a comet? Shattering it with a chunk of metal could be the answer, if a NASA mission due to be launched next week goes to plan. The Deep Impact spacecraft is due to take off from Cape Canaveral in Florida at about 18:48 GMT on Wednesday 12 January and will meet comet Tempel 1 roughly 134 million kilometres from Earth, just beyond the orbit of Mars. It will then release a 372-kilogram copper probe into the path of the comet. On 4 July, the comet and probe will collide at about 37,000 kilometres per hour, blasting a deep hole in the comet's nucleus that should reveal what lies beneath the icy surface. The porous surface of the comet should shatter on impac, spraying detritus outwards to leave a crater that could be 10 storeys deep and > 100 m wide. The craft will take just 6 months to travel a total distance of 431 million kilometres to reach the comet.

The probe carries a camera that will relay pictures of its death dive back to the Deep Impact mother ship, which will stay at a safe distance of at least 500 km to film the crash and use an array of instruments to analyse the debris. NASA's orbiting telescopes Chandra, Hubble and Spitzer will also watch the event, and the explosion generated by the $267-million mission should even be visible to telescopes on Earth. Comets are made of material left over from the formation of the Solar System, and astronomers say that studying the interior of Tempel 1 will allow them to step back > 4 billion years in time, giving them clues about the chemicals that formed Earth and its neighbouring planets. The probe, roughly the size of a washing machine, is made of copper to avoid contaminating the spray of ejecta caused by the impact. Copper is an element that no one trying to work out the origin of the Solar System cares about. It's not characteristic of any particular process. Astronomers know very little about the internal structure of comets, so tracking the impact should reveal much about their sturdiness. They are also unsure why comets eventually lose their characteristic tails, which are normally generated by the volatile chemicals that boil away from the surface as comets approach the Sun. Breaking into Tempel 1 could reveal whether these volatiles can become trapped by changes inside a comet's core. Because they are shrouded in huge clouds of gas, the relatively tiny nuclei of comets are best seen close up. 3 previous space missions have investigated the surfaces of comets Halley, Borrelly and Wild 2. The European Space Agency launched its own comet mission on 2 March 2004, and expects the Rosetta craft to arrive at comet Churyumov-Gerasimenko in May 2014, when it will drop a lander to study chemicals on the surface in more detail. Tempel 1 makes a convenient target for a faster mission because it passes through the inner Solar System once every 5.5 years. Discovered by French astronomer Ernst Tempel in 1867, it is about 6 km wide. Deep Impact's launch has already been delayed by problems with the craft's software, and a fault with the Boeing Delta II rocket that will boost it into space. Mission scientists hope that it will launch on 12 January, but it has until 28 January to leave Earth if it is to reach Tempel 1 in time to create the biggest 4 July fireworks display ever seen.
Comets are made of a loose collection of particles, like a weak sponge held together only by its own gravity. That is the conclusion of the Deep Impact team, who this week unveiled the latest results from their probe's smashing encounter with a comet. This spells bad news for the European Space Agency's Rosetta mission, which is aiming to land a probe on comet Churyumov-Gerasimenko in 2014. The lander, named Philae, might have a very hard time staying put on such a crumbly surface. I'm doubtful about how well a landing will work on this weak stuff. You could probably dig from one side to the other with your hands, it's that weak. The good news is that the analysis of the Deep Impact mission, which shot a 370-kg copper plug into the heart of comet Tempel 1 on 4 July, is helping to reveal secrets of the early Solar System as hoped. The make-up of the comet's innards, for example, implies that the Solar System was much more turbulent than we thought. The Deep Impact team announced their results on 7 September at the American Astronomical Society's Division of Planetary Sciences meeting in Cambridge, UK. When the Deep Impact probe punched into its comet, research teams were watching from around the world. Cameras recorded a bright plume of particles spraying out after the crash at about 5 km/s. This plume stayed close to the comet for some 22 hours before dispersing, from which the researchers could work out the mass and density of the comet's ice and dirt. They say the comet is about half as dense as water and is likely to be loose all the way through, with no hard lump at its core. Perhaps the most revealing data have come from the orbiting Spitzer Space Telescope, which took infrared measurements to see what chemicals lay inside the comet. We found material that has never been seen in comets before. Comets are formed from leftovers after the formation of the Solar System > 4.5 billion years ago. Spitzer saw that the comet's guts contained tiny particles of carbonate minerals and crystalline silicates. Both suggest that the particles must have formed in a much warmer environment, closer to the Sun, before migrating to the outskirts of the primitive Solar System where they slowly coalesced into comets. This means the young Sun would have been surrounded by a turbulent mess of viscous material. As the planets formed, they would have dragged this material around, causing streams of matter to flow from close to the Sun to the outer reaches of the Solar System. I used to think that you couldn't get this kind of mixing. Clearly we will integrate the results of Deep Impact into the way we conduct the Rosetta mission. Some are not confident that they've thought of the extreme case of this loose collection of microscopic particles. The Rosetta engineering team had prepared for the worst case scenario before the craft launched in March. Before we land, Rosetta will make a series of orbits around the comet to identify the character of the surface. After identifying the safest landing site, Philae will approach the comet at little more than walking speed, to avoid bouncing off. It's more of a docking manoeuvre than a landing. Philae also carries crampons to grab on to the surface. But the comet's gravity will be very weak. So if Philae is not firmly anchored, any sudden twitch of its drilling rig could send it spinning off into space
Web resources : NASA's Comet Observatory
Web resources :
• Introduction to comets
• The Armagh Observatory
• NASA's comet page
• NASA's Near Earth Object programme
• UK's Near Earth Object information
• Spacewatch
• Comets and Meteor Showers
• Comet facts
• antigravity : Could astronauts take a leaf out of H. G. Wells's book The First Men in the Moon, and use spacecraft propelled by antigravity devices? Some see the idea as science fiction, but major space agencies take it seriously. In 2001, the European Space Agency (ESA) commissioned 2 scientists to evaluate schemes for gravity control. They have concluded that, even if such control were possible, the benefits for lifting spacecraft out of the Earth's gravitational field would probably not be worth the effort^ref. But scientists working on such propulsion schemes dispute the report. NASA ran a research programme on speculative propulsion methods, called Breakthrough Propulsion Physics, from 1996 until its funding was cut in 2003. ESA report corrects some misconceptions in the field of gravity control, but its scope is too limited to rule out future research in the area. Conventional ideas for propulsion are much more effective. Antigravity seems to violate the law of conservation of energy, which prohibits perpetual motion. Place a wheel half over such a gravity shield and the shielded segment will rise, causing the wheel to rotate forever without a power source. What's more, gravity cannot be screened out in the same way as light or sound: Einstein's general theory of relativity explains that gravity results from the way mass distorts space-time itself. But relativity is not the last word on the subject. Gravity does not fit into the standard model of particle physics and we do not understand the gravitational interaction at the quantum level. ESA commissioned the survey of gravity control partly to establish whether a quantum theory of gravity might expose loopholes in our current understanding that space technology could exploit. Orfeu Bertolami and his co-author, Martin Tajmar of the space technology company ARC Seibersdorf in Austria, looked at proposals for assisting spacecraft launch by weakening gravity. They were not impressed. Experimentally and theoretically they do not seem to meet a standard we could qualify as scientific. All the same, the researchers did feel that some ideas for modifying gravity are worth exploring. For example, as they are reaching the edge of the Solar System, NASA's Pioneer spacecraft are deviating from their expected trajectories. This has led some scientists to suggest that the current theory of gravity is incomplete. There have also been suggestions that magnetic effects in materials whose behaviour is dominated by quantum effects, such as superconductors, might induce a kind of artificial gravity. NASA scientists have studied claims by Russian physicist Eugene Podkletnov that a spinning superconductor can act as a gravity shield, reducing the weight of an object placed above it by about 2%. Independent scientists have been unable to reproduce this and similar claims. They conclude that there are currently no good grounds for taking such effects seriously. All the same, they don't rule out the possibility of gravitational anomalies in quantum materials. Other options involve the gravitational and inertial masses of objects. Gravitational mass determines the force of gravity experienced by the object; inertial mass determines how much force is needed to set it in motion. General relativity says that the 2 definitions are identical, but some theories of quantum gravity suggest that they differ. Tajmar and Bertolami looked at schemes to alter one kind of mass, leaving the other unchanged. They found that reducing the inertial mass has no effect on the amount of fuel needed to launch a spacecraft. And altering the gravitational mass alone, by gravity shielding for example, doesn't help unless the shielding is almost total.
• cosmic fallout from a supernova 100 and 200 light years away dusted the Earth about 2.8 +/- 0.3 million years ago, and may have triggered a change in climate that affected the course of human evolution. The evidence comes from an unusual form of ⁶⁰Fe that was blasted through space by a supernova before eventually settling into the rocky crust beneath the Pacific Ocean. Comets and meteorites also deliver matter to Earth, but they always come from within our Solar System. Supernovae are the only known source of interstellar debris. The very fact that a supernova can dump material on the Earth demonstrates that the Earth is not independent of its cosmic environment. When the iron-60 arrived from space, it was evenly distributed all over the Earth. But the signatures are only detectable in crust that has lain undisturbed for millions of years, such as certain parts of the Pacific Ocean floor. This particular crust was taken from an area a few hundred kilometres southeast of the Hawaiian Islands in 1980. It was collected by oceanographers who were investigating the rocks as a potential source of rare mineral ores. The explosion can't have been too close to Earth, or it would have delivered enough radiation to cause mass extinctions. Conversely, if the supernova was any further away, more of the iron-60 would have been filtered out by the thin wisps of matter drifting between the stars. This means the supernova would have been at the right distance to spray out a stream of cosmic rays that could have increased the cloud cover on Earth. There may have been 15% more cosmic rays arriving on Earth than normal for at least 100,000 years. This is not enough to actually kill anything, but was perhaps sufficient to change the Earth's climate. The increase in cloudiness would have cooled the surface, tying up water as ice at the poles and leading to a dryer climate in Africa. Climate records in rock cores match the dates of the supernova event. Some people believe this climate change in Africa was a driving force in our own evolution. The argument is that a drier climate in the continent would have forced humans to adapt, and to spread out to other, wetter areas. The team is now looking for other unusual isotopes in the crust sample, which may reveal more about the type of star that caused the supernova. But there are probably 10,000 times fewer of these atoms than of the iron-60, so they will be extremely difficult to measure^{ref1, ref2, ref3, ref4}

Web resources :
• Korschinek on 'supernova archaeology'
• Fields on 'supernova archaeology'
• International Supernovae Network (ISN)
• exobiology : branch of biology concerned with the effects of extraterrestrial environments on living organisms
• the possibility that Earth's first life came here inside space rocks - the panspermia hypothesis - was proposed in 1903 by the Swedish chemist Svante Arrhenius. But the painful landing has always been a stumbling block. In 2002 it was demonstrated that soil bacteria can survive a high-speed impact into soft gel^ref. Most of the microbes died, but enough survived to make panspermia possible, provided that the bugs don't have to travel too far: they would probably be sterilized by cosmic rays and UV radiation during a journey from another solar system. But the researchers didn't know whether the pressures generated in their experiment were comparable to those of a meteorite impact. Nor did they know how different microbial species would fare. Cells or spores of the soil bacteria Rhodococcus erythropolis or Bacillus subtilis loaded inside lumps of rock (bits of porous ceramic, between 0.1 and 2 mm across) can survive impacts at speeds > 11 km/s (during impact, the bacteria are crushed by up to 1 million times atmospheric pressure). At similar pressures to those that would be suffered inside a meteorite as it crashed, around 1 in every 10 million R. erythropolis cells and a few in every hundred thousand B. subtilis survived when they hit the gel. A gram of terrestrial soil typically contains a billion bacterial cells. The survival rate for an ice target was about 10 times higher^ref, so it's not just Earth and Mars that could have swapped life. The icy moons of Jupiter, for instance (Europa and Ganymede : the former which has a sub-surface ocean of water), could seed one another. Or a planet could re-seed itself if, as some have suggested might have happened on the early Earth, a massive impact wiped out all life.
• the freezing and thawing of ice can turn polar rocks into a haven for microorganisms. Light-loving cyanobacteria flourish underneath around 95% of opaque glacial rock structures called polygons (which are rings of large, cracked boulders surrounding smaller rocks and soil) on Cornwallis Island and Devon Island in the Canadian high Arctic : repeated freezing and thawing of polar ice creates chinks in the boulders, which let just enough light through for the microbes to survive. On Alexander Island in Antarctica, 100% of outer boulders were colonized by cyanobacteria. But in the polygon's centre, where cracks are smaller, only 5% of rocks harboured the microbes. In fact, underneath the rocks is probably the best place for the microbes to live, as water is less likely to be whipped away by the biting wind.These bacterial communities may harness just as much energy from the Sun as the Arctic desert's scrubby lichens and mosses. These microbes can fix carbon compounds that then become available for other bacteria in the soil^ref. Meteor impacts, rather than being purely destructive, could also create oases for life by heating rocks and melting ice, either on Earth or on other icy worlds in the Solar System : cyanobacteria live in the rocks of the Haughton crater (a 24-km-wide dent made by an asteroid 23 million years ago) at far higher densities than in rocks found elsewhere. Asteroid impacts create the tiny pores by vaporizing certain minerals such as feldspar, leaving silicate-rich, perforated rocks behind. An asteroid crater could become an oasis for life because besides modifying rocks it also heats them, an effect that can last thousands of years. This could benefit polar deserts or even barren, icy worlds such as Mars or Titan. An asteroid impact could melt the ice and allow life, if its building blocks are present, to flourish. And the good thing about a hole in the ground is that water drains into it. Perhaps those scouring the Solar System for life should focus on impact craters, then. It might improve our chances of knowing where to look on Mars assuming that life on Mars is like life on Earth^ref
• species may have ended up on other planets : one way is contamination following space missions originating on Earth, a notion first put forward by Joshua Lederberg in the 1960s. But a poster presented by Andrew C. Schuerger of the Kennedy Space Center in Florida and colleagues suggest that at least one common contaminant of unmanned space missions, Bacillus subtilis, would not survive in large numbers, if at all, on Mars. The data followed on a previous study of the subject^ref
• Escherichia coli follows different adaptive pathways even under the same selection agent—strong UV radiation at levels simulating Mars : some strains make use of well known nucleotide excision repair (NER) genes such as polA, while others show mutations in radA. One UV-resistant strain showed 850 times the normal mutation in dnaE and dnaQ genes after exposure. The genotypic differences are all reflected in a phenotypic resistance
• contaminating Earth with material returned from comets, the Moon, and Mars : samples will be kept strictly contained from the surface of Mars to biosafety labs on the Earth. Life on Earth has evolved in the presence of material from Mars in the form of meteorites, which were probably not heated high enough to sterilize them on their way to the Earth
• early “evidence” of life on the Moon—seasonal patterns of light and dark and changing patterns of CO₂—date back to the 1920s and 1940s.
• a laboratory weighing no more than a toaster is being developed by British scientists to search for life on other planets. The system aims to use resilient plastic casts that can selectively recognize different organic molecules to pinpoint traces of organic carbon. The team, including Mark Sims of the University of Leicester, hope to secure a place for their device on board the European Space Agency's ExoMars mission, scheduled for launch in 2009. This isn't Sims' first experience with Mars. He was previously mission manager for the ill-fated Beagle 2 project. The Beagle 2 craft, which went missing during its approach to the red planet in late December 2003, was designed to look for life by measuring the weights of carbon atoms. A large proportion of lighter atoms is thought to indicate biological processes. Now Sims and his team are working on a different system. The Specific Molecular Identification of Life Experiment (SMILE) is being designed to search for molecules thought to indicate life (biomarkers). These range from complex hydrocarbons such as those found in crude oil, to amino acids and nucleic acids related to DNA. Should Sims and his team find amino acids, they will also try to work out whether they are left or right 'handed' molecules. Researchers think that an excess of one of these versions would indicate biological processes at work. The team hopes to find such molecules using an array of patches, each a fraction of a millimetre across, which are selectively sticky for just one biomarker. These patches could be made out of plastic films with molecule-sized cavities in their surface of just the right shape to accommodate a particular biomarker. Cavities such as this can be prepared by casting a polymer around a template biomarker. Some Earth-bound biosensors work on a similar principle, but use biological patches to trap selective molecules. Sims and colleagues point out that polymers are more robust, and so more likely to survive the harsh conditions of Mars. The polymers also don't pose any risk of contaminating the experiment or the planet with earthly biological material. The trick now will be refining a device to meet the accuracy and size requirements of a Mars mission. This requires substantial development work So they aren't completely ruling out the idea of using biological patches instead. The criteria for ExoMars are tough. Researchers hoping to get a place on the craft have to design a device that will look for biomarkers but not exceed 3 kg in mass or measure more than 16x16x20 cm. Even if the team meets these standards, they will still have politics to contend with. The status of ExoMars is currently up in the air, pending a decision to be made at a conference in December on whether such programmes should continue.  But the researchers intend to press on with SMILE regardless. It may find a home on a NASA mission, or have applications closer to home. It would have uses ranging from homeland security to forensic science. The technology would be particularly valuable for bio-prospecting in extreme environments on Earth, such as deep-sea hot vents, polar ice or deep in the planet's crust^ref. Aurora
• a physical object would be a more efficient way to send a long message to the stars than a beam of radio waves : it is well known that electromagnetic radiation—radio waves—can in principle be used to communicate over interstellar distances. By contrast, sending physical artefacts has seemed extravagantly wasteful of energy, and imagining human travel between the stars even more so. The key consideration in earlier work, however, was the perceived need for haste. If extraterrestrial civilizations existed within a few tens of light years, radio could be used for 2-way communication on timescales comparable to human lifetimes (or at least the longevities of human institutions). If haste is unimportant, sending messages inscribed on some material can be strikingly more energy efficient than communicating by electromagnetic waves. Because messages require protection from cosmic radiation and small messages could be difficult to find among the material clutter near a recipient, 'inscribed matter' is most effective for long archival messages (as opposed to potentially short "we exist" announcements). The results suggest that our initial contact with extraterrestrial civilizations may be more likely to occur through physical artefacts—essentially messages in a bottle—than via electromagnetic communication^ref. A stable orbit around Jupiter, or on the Moon or even the Earth could all be potential mailboxes - all locations occupied by the alien monoliths in Arthur C. Clarke's novel 2001. To send a message to a star system 1,000 light years hence, travelling at about 1 million kilometres per hour, would reach its destination after about 1 million years. The radio waves would be sent and received by giant radio telescopes. For simple messages, a radio transmission would use the least energy. But for a transmission of 100 terabits or more, it is easier to write. A message of 100 terabits could contain all the books in the US Library of Congress five times over. Rose argues that any message worth sending would exceed this easily - perhaps being closer to the 40 million terabits contained in all the world's telephone calls in a year. An inscribed object has the advantage of remaining legible no matter how far it travels, whereas even the narrowest beam of radio waves spreads out over interstellar distances, eventually becoming undetectable. For long messages over long distances, an alien civilisation is likely to send a package. We have sent several inscribed messages into space. The 2 Voyager probes each carry a long-playing record of "The Sounds of Earth"


, and both Pioneer craft, the first manmade objects to leave our Solar System, bear plaques charting their route, along with a picture of naked humans waving a greeting.

This plaque was launched with Pioneer 10 and 11 in 1972 and 1973 respectively. It was designed to explain to 'scientifically literate' aliens when the Pioneers were launched, who launched it, and where it came from.In the top left, a molecule of hydrogen is used to define a basic unit for both length and time. The starburst of lines represents the position of 14 pulsars, and their frequency at the time of launch - since a pulsar's rotation slows over time, this should allow the aliens to work out the age of the probe. The human figures are superimposed on a silhouette of the Pioneer craft for scale. The schematic of the Solar System shows the space probe's route before it ventured into interstellar space. Originally designed for a 21-month mission, Pioneer 10 exceeded all expectations and has lasted more than 30 years. The last time Pioneer 10 contacted us in 2003 it had travelled 12.2 billion km from Earth.
A similar alien salutation could be waiting on Earth for us.
Web resources :
• Chris Rose on inscribed matter
• SETI Institute
• 2001: A Space Odyssey
• Voyager Spacecraft
• the Search for Extraterrestrial Intelligence (SETI)@home project, in which volunteers use their home computers to sift through radioastronomy data for signs of intelligent broadcasts, reported its "most interesting signal" so far on September 2004, coming from between Pisces and Aries at a frequency of 1420 megahertz : scientists believe it is most likely to be due to random noise. Senior scientist Frank Drake conducted the first ever radio search for alien intelligence back in 1960. His name is familiar from his famous equation for estimating the number of civilizations in our galaxy that are trying to communicate with us. To Drake, the equation was merely a formalized way of showing all the things we do not know (It involves multiplying together a number of factors including the fraction of habitable planets on which intelligent life evolves, and the chances of those civilizations wanting to communicate with others). He drew up the equation simply as a way of organizing the discussions about extraterrestrial intelligence that took place in 1960 at the radio observatory in Green Bank, West Virginia. This was a meeting of visionaries, including Carl Sagan, physicist Philip Morrison and biochemist Melvin Calvin. The previous year, in Nature, Morrison and his colleague Giuseppe Cocconi had proposed the idea of searching the skies for alien messages^ref, and Drake, with Sagan and others, went on to found the SETI Institute in 1984. The Drake equation has become a touchstone of SETI efforts. But, as with so many things in this area, it has been interpreted far beyond its intended use. It is regularly quoted as if it were a formal proposal, and searching for aliens were a quantifiable science. SETI's defenders point out that it costs nothing. The SETI Institute in Mountain View, California, is privately funded and the Allen Telescope Array currently under construction in California, which will carry out standard radioastronomy as well as SETI searches, is being supported by a US$13.5 million donation from Microsoft cofounder Paul G. Allen. And in terms of getting school children interested in science, searching for aliens beats even dinosaurs. The interest raised by false alarms is a problem.
• European scientists have sent a 'cyborg' to roam the Spanish countryside as part of a mission to create robots that are good at exploring planets independently. Researchers at the Centro de astrobiologia near Madrid kitted out a human with a camcorder linked to a computer system programmed to look for interesting features in the landscape. The human merely did the donkey-work of carrying the hardware while the computer did the 'thinking'. On a planetary mission, a robotic vehicle such as NASA's rovers Spirit and Opportunity, currently touring the surface of Mars, would carry the hardware. Initial field tests of this cyborg astrobiologist showed that the computer-controlled vision system could identify some of the same geological features that human geologists would have selected as being worthy of closer study. The computer selects its targets using an 'uncommon map', which is an analysis of the features in an image that least resemble the rest of the picture. Proponents of human space exploration often argue that robots are no match for trained astronauts and geologists in spotting promising study sites and responding to chance discoveries. But if the current work fulfils its promise, future robotic explorers will have a decision-making capacity similar to that of human experts. Robotic explorers would be useful, not just on Mars, but also on more remote and inclement worlds, such as Jupiter's icy moon Europa and Saturn's haze-shrouded moon Titan, which NASA's Huygens spacecraft is due to explore early next year. The Spirit and Opportunity rovers are controlled from Earth by programming them at the beginning of each martian day with all the moves they must execute before they shut down to conserve power during the night. The vehicles have some degree of autonomy, however. For instance, they might be programmed to go to a particular location, but in getting there they are free to execute spontaneous manoeuvres to avoid obstacles. Even so, this makes the rovers very single-minded. If they were to encounter an interesting site en route, or to spot a destination that looks more promising that the programmed one, they would not be able to act on their own initiative. The astrobiologist programme aims to develop a system that has this kind of flexibility and 'intelligence'. The system's mapping software, developed by the Madrid team and computer scientists at the University of Bielefeld, Germany, mimics the behaviour of real geologists scanning a new scene. They tend to pay most attention to areas that stand out as different from the rest. The hardware is all wearable by a single person, and the researchers tested it at a cliff face in Madrid's Southeast Regional Park. To find truly 'interesting' areas on the cliff face, the cyborg system has to overcome various challenges. For example, it has to be able to distinguish shadows from areas of genuinely different rock colour. It has to be able to 'remember' what it found initially interesting as it zooms in on a certain candidate site; a region that stands out at a distance might look blandly uniform close up. And it has to decide what kind of differences to look for: colour, texture or light intensity, for instance. The researchers have yet to develop an intelligent zoom facility for the camera, for example. They are encouraged, however, that on one field trip the system identified precisely the spot on the cliff face that the geologists in the team agreed was the most promising, where water had seeped out of the rock to darken its surface. Spotting a feature like this would be particularly important in the search for water on Mars. Other groups are working on similar 'robot geologists', for example at NASA's Ames Research Center in Mountain View, California. "They may be a little more advanced," he admits, but he points out that his "baby geologist" has the virtue of being unbiased: it simply looks for stand-out features rather than being preprogrammed to find, say, a specific type of mineral. The Madrid team's system is now scheduled to explore Spain's Rio Tinto area, where the highly acidic and iron-rich ground water is thought to mimic some of the extreme conditions on other planets. In collaboration with NASA, scientists at the Centre for Astrobiology are planning to drill a hole several metres deep and to send a worm-like robot to seek out interesting features in the underground rock.
• An autonomous robot has found life in one of the most lifeless places on Earth: the Atacama desert in northern Chile, thought to be a close analogue of Mars's arid surface. An expedition team from Carnegie Mellon University in Pittsburgh, Pennsylvania, found that the life detection system worked very well, and something like it may ultimately enable robots to look for life on Mars. The 4-wheeled droid, called Zoë, found colonies of bacteria and lichens in 2 different parts of the desert, which has the least amount of organic material anywhere in the world. Scientists back in Pittsburgh sent commands to guide Zoë's exploration each day, but she relied on her own cameras and internal sensors to navigate the tough terrain. As she looked for signs of life, fellow researchers in the desert followed to check her results. There is not a single example of the rover giving a false positive. The scientists' expedition to Atacama in September and October 2004 was part of NASA's astrobiology programme. They presented their results at the 36th Lunar and Planetary Science Conference in Houston, Texas. Zoë looks for life by detecting fluorescence from biological molecules such as chlorophyll. It can also spray dyes on to the ground that light up when they bind to chemicals such as the nucleic acids found in DNA, or the amino acids in proteins. The robot carries a camera on her underside to take pictures of the finds. Although fluorescence sensing is standard technology in the lab, sunlight easily disrupts the measurements. This is a problem for any martian rover that relies on solar power, as it can only explore in the daytime. So Zoë's dyes are probed with high intensity flashes of light and her camera opens only at the precise moment of fluorescence. Its fluorescent imager is the first such system to work in the daylight while in the shade of the rover. Even better, the samples do not have to be scooped into an analysis chamber, and this speeds up Zoë's experiments. "Other testing methods require considerably more sampling or are less sensitive. The rover can spot patches of just a few thousand bacteria. Atacama is a popular test area for martian life probes, because intense UV light and strong oxidants in the soil quickly break down organic molecules, just as on Mars. The signs of life that Zoë found actually lie below the detection limits of NASA's 2 Viking landers that arrived on Mars in 1976, but several teams are extending such limits. For example, Richard Mathies, a chemist at the University of California, Berkeley, has recently tested Atacama soil in the laboratory using his own team's amino-acid detection system : their 'life chip' could sense concentrations of amino acids down to 10 ppb, > 1,000 times the sensitivity of the Vikings' system^ref. Zoë has certainly proved successful, but some of the sites the robot visited have visible lichens on rocks. In the sites they visited these obvious signs of life were not present. Zoë returns to Atacama in August 2005 for her toughest assignment yet: to autonomously cover 50 km over 2 months, sampling the soil as she goes.


Web resources :
• The Joshua Lederberg Papers : Exobiology
• dmoz Open Directory Project (ODP) : Exobiology
• Crop circles
• Committee on the Origins and Evolution of Life (COEL)
Bibliography :
• Nature Insight Astrobiology in Nature Vol.409 22 February 2001
• the solar system


2 sets of astronomers have spotted a new planetoid in the outskirts of our Solar System. It is the brightest object in the region after Pluto, and it has its own small moon. It isn't too uncommon to find such objects lurking in the icy Kuiper belt, the region of space beyond Neptune that is filled with rubble left over from the formation of our planetary neighbourhood some 4.5 billion years ago. In recent years astronomers have spotted several Kuiper-belt planetoids, including ones named Quaoar and Varuna; the latest has been nicknamed Santa. Philosophical debates continue about how large such objects have to be before we call them 'planets' rather than simple lumps of rock. Provisionally named 2003 EL61, it was first seen in 2003 by Jose-Luis Ortiz, an astronomer from the Institute of Astrophysics in Andalusia (IAA), Spain, and his colleagues. They used the Sierra Nevada Observatory in Granada, Spain, and observations this month confirmed its existence. The object had also been spotted by a group at the California Institute of Technology in Pasadena, led by astronomer Mike Brown. They first saw it on 28 December 2004, hence its seasonal sobriquet. Ortiz describes it as a "very bright, slowly moving object", which is > 1,500 km across. This makes 2003 EL61 bigger than Pluto's moon Charon, as well as other known Kuiper-belt planetoids. It is so bright that Brown estimates it might be visible using an amateur telescope. Follow-up observations with Spitzer made on 22 July should deliver a precise size for the planetoid soon. Also Santa has a small moon, after more observations in January 2005 from the Keck Observatory in Hawaii. The moon orbits its planetoid once every 49 days at a distance of 50,000 km. This information allowed calculate that it makes up just 1% of the entire mass of the pair, making it much, much smaller than Charon. The mass of the planetoid itself is around 4 exatonnes (4 x 10¹⁸ tonnes): a third the weight of Pluto and about the same mass as all the water on Earth. The object spends about half of its time outside Pluto's orbit, and half its time closer to the Sun. Brown will present further details of the planetoid and its moon at the American Astronomical Society's planetary sciences meeting in Cambridge, UK, on 8 September 2005^ref. The discovery of a new addition to our Solar System has prompted astronomers to fast-track plans to decide what is and is not a planet. The rules could more than double the number of local planets - or they could demote Pluto, leaving us with only 8 in our neighbourhood. The number of planets appeared to rise to 10 on 29 July 2005, when US astronomers announced the discovery of 2003 UB313, a chunk of rock and ice that orbits near Pluto, around 15 billion km from the Sun. The body is so big it must surely qualify as a planet. A name has been submitted to the International Astronomical Union (IAU). But the IAU, which oversees the naming of stars and asteroids, has no criteria for defining planets. An IAU committee has been working on the issue for around a year and had planned to publish its results next summer. Brown's discovery has made the debate more urgent. Most planets in the Solar System are either solid, such as Mercury, Venus, Earth, and Mars, or gas giants, such as Jupiter, Saturn, Uranus and Neptune. But Pluto and 2003 UB313, both rocky worlds that lie beyond the gas giants, fall into a final and controversial group. When discovered in 1930, Pluto was thought to exist alone. Astronomers now know it lies in the Kuiper Belt, a jumble of rocky and icy objects that rings the Sun. New objects are continually discovered in the belt. And several Kuiper Belt objects are a similar size to Pluto - 2003 UB313 is thought to be larger. If Pluto is a defined as a planet, then around ten other Kuiper Belt objects should presumably also qualify. But many astronomers object to this, and argue that Kuiper Belt objects should have a separate status. Gas giants and terrestrial planets are much larger than Kuiper Belt objects, and don't exist in a ring of debris. If the committee follows this reasoning, Pluto could lose its traditional status. The orbits of the inner planets also lie in the same plane. But 2003 UB313 and some other Kuiper Belt objects are in a wildly different orbit, at nearly a 45° angle to the rest. Some experts say this wouldn't necessarily discount it as a planet. astronomers cannot control what gets called a planet. Our culture has fully embraced the idea that Pluto is a planet and scientists have for the most part not yet fully realized that the term 'planet' no longer belongs to them. Everyone should ignore the distracting debates of the scientists, and planets in our Solar System should be defined not by some attempt at forcing a scientific definition on a thousands-of-years-old cultural term, but by simply embracing culture. Pluto is a planet because culture says it is, and that means his new find is a planet too.
A recently discovered planetoid on the outskirts of our Solar System is turning so fast that it seems to have been squeezed into the shape of a cigar. And this cigar looks as if it is spinning not around its long axis, but around its middle. This is such a bizarre situation that some refuse to believe it. The object, known as 2003 EL61 and nicknamed 'Santa', is a bit smaller than Pluto, has its own moon, and spends half of its time outside Pluto's orbit, and half of its time closer to the Sun. Its existence was announced in July by two teams of astronomers. But further observations by one of the teams have now revealed the strangest characteristic of this new planetoid: it is spinning at an unprecedented speed for something of its size, giving it a 'day' of just 3.9 hours. That rotation makes it stretch. The Earth bulges similarly at the equator because of its rotation, but it has spread out evenly, like a rugby ball. Theory predicts that a very rapidly spinning body could bulge out along just one axis, and this seems to be what has happened to 2003 EL61. One possibility is that the planetoid recently collided with a massive chunk of rock, suggests Grav, speeding it up and encouraging elongation along one axis. Rabinowitz's team hopes that further observations with the Hubble Space Telescope will confirm its shape. The team has considered the possibility that the elongation might be an optical illusion, caused by having another moon orbiting extremely close to the planet that periodically blocks reflected light, but that system wouldn't be stable. Others say it might be an illusion caused by variation in surface materials on different sides of the planet. The astronomers are not yet sure what the planetoid is made of, although it seems to be a mix of water ice and rock. The surface is mostly covered with ice, which is probably cracked from the stresses of the rotation. If it is indeed the shape it looks, then it might some day snap in 2. It's very close to being unstable. If you spun a body twice as fast, it would probably turn into 2 bodies.
Astronomers say they have found a new planet in our Solar System, the first one bigger than Pluto since that object was discovered in 1930. The planet is also further away than Pluto, the furthest known planet. It’s the first object bigger than Pluto ever found in the outer solar system. The planet, temporarily named 2003UB313, was found in an ongoing survey at Palomar Observatory’s Samuel Oschin telescope. The observatory is on the Palomar Mountain near San Diego, Calif. The group has proposed a name for the new planet to the International Astornomical Union, the organization in charge of nomenclature of celestial objects. A few other planet-like Solar System objects have been discovered since Pluto was identified, but none are bigger than Pluto, and astronomers don’t agree on whether to call them planets. They’re thought to be something between planets and asteroids.  No precise definition of planet exists, actually. Scientists are debating what such a definition would be; there are a wide variety of Solar System objects, and few clear divisions between the different types.  Pluto itself, while historically considered a planet, is more correctly termed a “Kuiper Belt Object”. The Kuiper Belt is an area of the solar system outside Neptune’s orbit, and which is believed to contain asteroids, comets, and icy bodies. One possible definition of “planet” that some astronomers have discussed includes any newfound Solar System object larger than Pluto. So by this definition, the object that Smith and colleagues say they found might be considered a planet. If so, and if Pluto is also a considered planet, this makes the newfound body the 10th known planet. Currently about 97 times further from the sun than the Earth, it is also the farthest-known object in the solar system, and the third brightest Kuiper Belt Object. It will be visible with a telescope over the next six months and is currently almost directly overhead in the early-morning eastern sky, in the constellation Cetus. Brown, Trujillo and Rabinowitz said they first photographed the new planet on October 31, 2003. But it so far away that its motion was not detected until they reanalyzed the data last January. Since then, the scientists said, they have been studying the planet to better estimate its size and its motions. Scientists can infer the size of a solar system object by its brightness, just as one can infer the size of a faraway light bulb if one knows its power. The reflectance of the planet is unknown. Scientists can not yet tell how much light from the sun is reflected away, but the amount of light the planet reflects puts a lower limit on its size. Even if it reflected 100% of the light reaching it, it would still be as big as Pluto,” said Brown. “I’d say it’s probably one and a half times the size of Pluto.
Web resources :
• Solar System Tour
• GPS
• Planetary Names
• Division of Planetary Science meeting
• International Atronomical Union: Minor Planets
• Sun (1,390,000 km = 864,990 miles in diameter; mass: 1.989³⁰ kg; temperature: 5800 K (surface) and 15,600,000 K (core). It contains more than 99.8% of the total mass of the Solar System (Jupiter contains most of the rest). The Sun is, at present, about 75% hydrogen and 25% helium by mass (92.1% hydrogen and 7.8% helium by number of atoms); everything else ("metals") amounts to only 0.1%. This changes slowly over time as the Sun converts hydrogen to helium in its core. The outer layers of the Sun exhibit differential rotation: at the equator the surface rotates once every 25.4 days; near the poles it's as much as 36 days. This odd behavior is due to the fact that the Sun is not a solid body like the Earth. Similar effects are seen in the gas planets. Conditions at the Sun's core are extreme. The temperature is 15.6 million Kelvin and the pressure is 250 billion atmospheres. The core's gases are compressed to a density 150 times that of water. The Sun's energy output (3.86³³ ergs/second or 386 billion billion megawatts) is produced by nuclear fusion reactions. Each second about700,000,000 tons of hydrogen are converted to about 695,000,000 tons of helium and 5,000,000 tons (=3.86e33 ergs) of energy in the form of gamma rays. As it travels out toward the surface, the energy is continuously absorbed and re-emitted at lower and lower temperatures so that by the time it reaches the surface, it is primarily visible light. For the last 20% of the way to the surface the energy is carried more by convection than by radiation. The surface of the Sun, called the photosphere, is at a temperature of about 5800 K. Sunspots are "cool" regions, only 3800 K (they look dark only by comparison with the surrounding regions). Sunspots can be very large, as much as 50,000 km in diameter. Sunspots are caused by complicated and not very well understood interactions with the Sun's magnetic field. A small region known as the chromosphere lies above the photosphere. The highly rarefied region above the chromosphere, called the corona, extends millions of kilometers into space but is visible only during eclipses. Temperatures in the corona are over 1,000,000 K. In addition to heat and light, the Sun also emits a low density stream of charged particles (mostly electrons and protons) known as the solar wind which propagates throughout the solar system at about 450 km/sec. The solar wind and the much higher energy particles ejected by solar flares can have dramatic effects on the Earth ranging from power line surges to radio interference to the beautiful aurora borealis. The solar wind has large effects on the tails of comets and even has measurable effects on the trajectories of spacecraft. Spectacular loops and prominences are often visible on the Sun's limb. The Sun is about 4.5 billion years old. Since its birth it has used up about half of the hydrogen in its core. It will continue to radiate "peacefully" for another 5 billion years or so (although its luminosity will approximately double in that time). But eventually it will run out of hydrogen fuel. It will then be forced into radical changes which, though commonplace by stellar standards, will result in the total destruction of the Earth (and probably the creation of a planetary nebula). There are nine planets and a large number of smaller objects orbiting the Sun. (Exactly which bodies should be classified as planets and which as "smaller objects" has been the source of some controversy, but in the end it is really only a matter of definition.)
• sunspot : direct observations of their numbers are available for the past 4 centuries, but longer time series are required, for example, for the identification of a possible solar influence on climate and for testing models of the solar dynamo. The level of solar activity during the past 70 years is exceptional, and the previous period of equally high activity occurred more than 8,000 years ago. During the past 11,400 years the Sun spent only of the order of 10% of the time at a similarly high level of magnetic activity and almost all of the earlier high-activity periods were shorter than the present episode. Although the rarity of the current episode of high average sunspot numbers may indicate that the Sun has contributed to the unusual climate change during the 20th century, solar variability is unlikely to have been the dominant cause of the strong warming during the past 3 decades^ref.
• solar sails are spacecraft without engines. As the Sun's light beats down on the sheet's surface, each photon transfers a small amount of momentum to the sail, accelerating it away from the Sun. The energy involved is tiny, but over considerable time it can boost the sail to tremendous speeds because there is no friction in deep space to slow the craft down. The Institute of Space and Astronautical Science (ISAS), a division of JAXA, launched the sails in a small S-310 rocket from Uchinoura Space Center in Kagoshima, Japan, at 6:15 GMT on August 10, 2004. At 100 seconds after lift-off, the rocket reached an altitude of 122 kilometres, where it released the first sail. This successfully opened to make a clover-leaf shape about 10 metres across, which was then jettisoned to float through space. A second deployment opened the next sail like a pleated fan at an altitude of 169 kilometres. Both sails burned up as they entered the Earth's atmosphere moments later, and the rocket splashed down in the Pacific Ocean about 400 seconds after lift off. The Japanese experiment is quite similar to a Russian space sail, called Znamia, which was released from the Mir Space Station in 1993. But this week's launch tested improved ways of folding a sail, which are crucial for efficiently packing the structure into a small rocket and then deploying it in space. At only 7.5 mm thick, the sails are about 10 times thinner than a sheet of paper. JAXA had already tested their 'fan' deployment method in balloon tests last year, proving that they reign supreme in space age origami. "The Japanese are of course famous for their folding technology. Solar sail technology has proved difficult to realize because the sail must be large enough to catch the Sun's rays, while still being extremely lightweight and strong. To achieve meaningful propulsion the sail would have to measure more than 50 metres across and weigh < 100 kg. There is still a long way to go before we see a solar sail mission to the stars, because the exact force that the Sun's rays can exert on a sail remains unknown. For a proper test of solar sail technology, it must be launched at least 1,000 km from the Earth's surface. Any closer and there might be interference from gas molecules at the wispy limits of the Earth's atmosphere that could obscure the tiny forces delivered by solar photons. In April 2005, if all goes to plan, a 600 m² Mylar sail called Cosmos 1, which looks more like a windmill than a starship, will prove that a spacecraft can be propelled by sunlight alone. First, though, it will have to be launched into orbit on a converted missile from a Russian nuclear submarine in the Barents Sea. Cosmos 1 is privately funded by the Planetary Society, a US space-advocacy group based in Pasadena, California, which Friedman heads, but it was built in Moscow by the ex-Soviet aerospace company NPO Lavochkin. After the sail reaches its initial 800-km orbit and unfolds its 8 triangular vanes, ground controllers will tilt the vanes like sailors feeling for the wind. A slight boost to the spacecraft's orbit is all they need to demonstrate propulsion by light pressure. It may take a few days, but the Cosmos team won't mind waiting. Solar sails accelerate almost imperceptibly at first, as photons of light bounce off their enormous reflective surface, imparting momentum. But, unlike conventional rockets, they can accelerate continuously, and keep accelerating as long as the Sun is shining, without needing a drop of fuel. After 1 day, the velocity increase for an interplanetary sail would be a modest 160 km/hr. After 100 days, the sail would be moving at 16,000 km/hr. In 3 years it would be travelling 160,000 km/hr, 3 times faster than the Voyager spacecraft now exiting the Solar System, and fast enough to reach Pluto in < 5 years — half the time the NASA New Horizons mission will take to reach Pluto. In the 1970s, Friedman was a project manager at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, where he led the conceptual design of a US mission to Halley's Comet, using a gigantic 640,000 m² sail. The idea was shot down by NASA management as too risky. After leaving JPL, Friedman co-founded the Planetary Society with scientists Carl Sagan and Bruce Murray in 1980. While pushing the society's agenda of international space cooperation, he built solid friendships and working relationships with Russian space scientists and engineers, at a time when such relations were viewed with suspicion. Later, it made economic and technical sense for the Planetary Society to turn to Russia for help on the solar-sail project. The missile launch was a bargain; NPO Lavochkin was already working on inflatable spacecraft (the masts that hold the Cosmos 1 sail must inflate in space), and Russian interest in solar sails dates back to the visionary Konstantin Tsiolkovsky, who wrote about them as early as 1921. Right now, Friedman is trying to balance his excitement at getting this far, with more realistic expectations. The project's tiny US$4-million budget has meant cutting corners on certain materials and the number of design reviews. But the team is made of capable, experienced people who have tried to anticipate everything that could go wrong. After one technical review in Moscow, recalls Friedman, a Russian consultant gave Cosmos 1 as much as a 70% chance of succeeding. Unfortunately, the team missed its chance to test the sail's deployment on a suborbital launch in 2001, when the spacecraft failed to separate from its rocket, and both were lost at sea. Instead of repeating this short flight, Friedman and his colleagues decided to go straight to orbit for their next try. Although NASA wouldn't approach a high-risk project in this way, the agency will be cheering Cosmos from the sidelines. Placing a spacecraft in a close polar orbit around the Sun, for example, requires enormous amounts of rocket fuel to fight the inward pull of solar gravity. Solar sails would act as natural brakes, and would never run out of fuel. But there is a big gap between dreaming and doing. Most plans for solar sails have never got anywhere near the Sun. In 1992 there was talk of an international solar-sailing regatta to celebrate the 500th anniversary of Columbus's voyage to America. Groups including the Pasadena-based World Space Foundation got as far as building and testing sails on the ground, using a mix of professional and amateur labour, but their money dried up. More recently, a Texas-based group called Team Encounter announced plans to attach paying customers' messages, drawings, photographs and DNA samples to a sail and send it off into interstellar space. None of these projects has come close to launching. In terms of flight experience with solar sails, Japan is the world leader until Cosmos 1 launches. Last August the Japanese Aerospace Exploration Agency (JAXA) conducted a brief suborbital test on a sounding rocket, during which two 10-m sails unfurled from a mast to form a pinwheel shape. In May the agency will test a 20-m sail suspended from a scientific balloon at an altitude of 35 km. JAXA's ultimate goal is a hybrid propulsion system combining solar sailing with ion-drive engines. One proposed JAXA mission would combine a 50-m solar sail with an ion drive to place a probe in orbit around Jupiter's poles and fly past several asteroids. Of the many technical challenges facing solar sails, dynamics is perhaps the most vexing. No one knows exactly how stable it will be, or whether it will twist and curl on itself like a flimsy kite in a strong wind. If Cosmos 1 reaches a higher orbit and meets all its other mission objectives, it will be used for one last, futuristic experiment. University of California physicist and science fiction writer Gregory Benford, along with his brother James, president of Microwave Sciences in Lafayette, California, will aim a 450-kW microwave beam from a radio antenna in the Mojave Desert towards the sail. They hope the beam will give an extra push to the sail. Someday, that method may be used to propel gossamer sails more quickly to other planets, and perhaps even other stars. A successful Cosmos 1 mission would give a gentle push to solar-sail projects within the space agencies. The earliest NASA could fly a solar sail is 2009 on the Space Technology 9 demonstration mission, although other technologies will be competing for that flight. No one knows exactly how stable it will be, or whether it will twist and curl on itself like a flimsy kite in a strong wind. Among NASA's long-term solar-sail proposals are the Particle Acceleration Solar Orbiter, which would orbit close enough to the Sun to keep a steady gaze on active solar regions, and a Solar Polar Imager for studying the Sun's higher latitudes. NASA and the National Oceanic and Atmospheric Administration would also like to put weather stations in stable orbits between Earth and the Sun to give advance warning of sunstorms. These would need sails 3-5 times bigger than Cosmos 1. The European Space Agency is interested in solar sails too, for reasons similar to NASA's — to place an orbiter around the poles of the Sun. The agency is also studying another mission concept called Earthguard to visit near-Earth asteroids. Although no solar-sail missions have yet been approved, Van Sant is spending about $10 million a year laying the technological groundwork. This year 2 pioneers of solar-sail development, L'Garde of Tustin, California, and ABLE Engineering of Goleta, California, will test different designs for 20-m sails in a giant vacuum chamber at NASA's Plum Brook facility in Ohio. ABLE's sail is made of an extremely thin new polymer called CP-1, only 2.5 mm thick — half as thick as the aluminized Mylar on Cosmos 1. Thinner and lighter is better when it comes to solar sails, but flimsy films are also more prone to tearing. Even the reinforced sails of Cosmos 1 won't last forever: within a month of launch they will begin to degrade in the harsh sunlight. But the short flight should be long enough to demonstrate the principle of solar sailing, and if successful will open the heavens to other solar-powered craft.

Web resources :
• Planetary Society: Solar Sail
• German Aerospace Centre Solar Sail Project
• 2004 Solar Sail Technology and Applications Conference:
• solar winds : the stream of energetic particles thrown off by the Sun, responsible for comets' tails. As a comet approaches the Sun, the particles warm up its surface and push a stream of ionized material outwards, forming a distinctive tail that can be 200 million km long. Solar flares frequently burst from around sunspots, releasing extra energetic particles into the wind. But coronal mass ejections are the most impressive of the Sun's emissions. These ejections boost the solar wind to gale force, as the star's magnetic field opens up and allows huge amounts of hot plasma to escape into bubbles that are sometimes as large as the Sun itself. If these outbursts reach Earth, they can damage communication satellites and even cause power grids to fail. Although several satellites already monitor solar activity in our region of the Solar System, comets could provide useful information about the effects of coronal mass ejections farther away from the Sun. After seeing photographs of the comet Ikeya-Zhang in which its tail was disturbed, Jones and Brandt looked back over observations made by the Solar and Heliospheric Observatory (SOHO), a satellite operated jointly by NASA and the ESA. Massive eruptions from the Sun on 2 March, 9 and 10 March, and 17 April 2002 all preceded disturbances in the comet's tail by 1 or 2 days. Each tail disturbance lasted for < 1 hour. Over those 6 weeks, comet Ikeya-Zhang moved from being about 75 million kilometres away from the Sun to almost 150 million km away (the Earth is about 150 million kilometres from the Sun). From these observations, the astronomers worked out that the eruptions must have thrown out matter at up to 1,131 km/s. By comparison, the fastest known solar winds only reach about 800 km/s. Records of Halley's comet from 1910 and 1985 have patterns in its tail that could be explained in a similar way. Astronomers might use old comet photographs to reconstruct the frequency of these solar eruptions over time. The solar wind is thought to have been unchanged for 4.5 billion years. We need to know the starting composition to find out how the Solar System formed. A NASA project designed to bring back samples of the solar wind to Earth ended with a disappointing crash at 10:00 in the desert of Utah on Sep 10, 2004 at > 200 km/hr. The broken capsule spells the end for a 3-year, US$260-million experiment. Initial speculation has focused on a battery on board Genesis, which had been overheating since shortly after launch in 2001. But a similar battery performed well at these higher temperatures in the lab. Had the battery failed, it would have prevented a small explosive from freeing the craft's parachutes. Researchers will be especially keen to find the root of the problem, as NASA's Stardust mission will use a similar parachute system. The mission, which has successfully collected material from a comet's tail, is due to return to the same spot in Utah as Genesis in 2006. Should any samples be retrieved from the craft, they will be the first to be brought back from space since the Apollo missions to the Moon in the 1970s. Scientists hope such samples will give them a glimpse of what the Solar System was like when it was born. Initial inspections show that the craft split open on landing, exposing many of the detectors to contamination by Earth's air and soil. Many of the fragile wafers of gold, silicon, diamond and sapphire inside the craft were also smashed to bits. But scientists expect to be able to piece together many of the broken wafers. And it should be possible to wipe away molecules of air from the wafer surfaces, although if dirt has landed on them, they will prove harder to clean. Scientists are glad, at least, that it was not raining. It would have been very difficult, if not impossible, to rid the detectors of contamination by water. A stream of particles from the Sun, in combination with extreme weather conditions, caused an unprecedented thinning of the upper Arctic ozone layer in 2004. Scientists have been puzzled by the chemical processes that destroyed up to 60% of ozone molecules in the lower mesosphere and upper stratosphere (the atmospheric layers that lie 30 to 40 km above ground) in the first months of 2004. Reactions with chlorofluorocarbons (CFC), the compounds responsible for ozone depletion in the lower stratosphere, could not explain the decline in higher layers. Strong solar storms in October 2003 carried energetic electrons and protons into the Earth's upper atmosphere, where they boosted production of nitrogen oxides (NOx) by a factor of 4. Very strong winds inside the polar stratospheric vortex, which was exceptionally powerful last winter, then transported the excess nitrogen gases further into the atmosphere. At around 40 kilometres' height, they mixed with, and attacked, the ozone layer. Ozone is a form of oxygen that shields the Earth from dangerous UV radiation from space. Ozone holes were first detected in the 1980s above the South Pole. Soon afterwards, CFCs were phased out under the 1987 Montreal Protocol. Ozone holes do still occur regularly in the Antarctic, but at high northern latitudes they are observed only in particularly cold winters^ref. Nitrogen-oxide-rich air first began to descend in January, and led to strong ozone depletion between March and May. The effect was still present in July, but declined as the stratospheric vortex broke up later in the year. Whether the full magnitude of the anomaly can be explained by the extra injection of solar particles must still be investigated^ref. Determining the influence of solar particles on the composition of the atmosphere is crucial for understanding the links between solar activity, ozone depletion and climate. A study to determine the influence of solar-particle fluxes on the chemistry of the atmosphere based on a 14-year data series is currently under way in Germany. Such work might help explain why existing atmosphere models have not matched observed ozone losses during several cold Arctic winters over the past decade. Despite strong depletion in the upper ozone layer, a full-fledged ozone hole did not occur in the Arctic in 2004, thanks to relatively warm temperatures. But although solar activity has now calmed down, scientists expect significantly larger ozone losses in 2005, which has so far been exceptionally cold.

Web resources : Ozone depletion at EPA
• Mercury (0.387 AU from Sun)
• Venus (0.723 AU from Sun)
• Earth (1 AU from Sun; diameter : 8,000 miles)
• the most comprehensive and detailed topographic map of Earth ever made has been completed. The elevation data just released cover areas that have never been mapped in three dimensions before, and should be useful in predicting the effects of climate change and sea-level rise. The Shuttle Radar Topography Mission (SRTM) is a collaboration between NASA, the US National Geospatial-Intelligence Agency and the German and Italian space agencies. It uses radar interferometry, which combines images taken at slightly different locations to produce a single 3D image. The method works in the dark, and also penetrates clouds, so it can map the areas persistently covered by clouds that are inaccessible to satellite photography. The space shuttle Endeavour collected images of 80% of Earth's surface (from 56º S to 60º N) using radar antennas both in the shuttle's main bay and at the end of a 60-metre mast. It's probably the most significant scientific mission the shuttle programme has ever done. It has taken 4 years to process all the data obtained during the 11 days that the shuttle orbited the planet, but now all of the images are complete. The latest additions cover Australia and New Zealand, and reveal terrain previously unmapped, such as regions of South America and islands in the South Pacific. The elevation data should help disaster planners on such islands respond to storm surges and rises in sea level. Knowing exactly where rising waters will go is vital for mitigating the effects of disasters like the Indian Ocean tsunami. The images will also be helpful in studying erosion, landslides, ecological zones, and climate change. The elevation data could be used for planning and simulating military missions, determining where to construct communication towers and creating virtual topographic displays in aeroplane cockpits. And they should help to create better maps for backpackers, fire-fighters, geologists and natural resource managers

Web resources :
• Shuttle Radar Topography Mission (SRTM) - NASA site
• Shuttle Radar Topography Mission (SRTM) - USGS site
• USGS topography database
• our planet may have frozen over in the past as it drifted though giant dust clouds in space. The result of the dust-bath would have been an almost complete overcoat of ice for the world. A group of US and Russian researchers argue that interstellar dust might have accumulated in Earth's atmosphere and cooled the planet, tipping the climate towards a 'snowball Earth' event in which ice sheets keep growing until they cover almost the entire globe. But the idea does not persuade some geologists as it conflicts with the geological record. There seem to have been dramatic changes in the Earth's carbon cycle up to a million years before known snowball Earth events, which the dust-cloud hypothesis is at a loss to explain. The climate-cooling mechanism is almost inevitable, however. On at least 2 occasions in the past 2 billion years, the Solar System must have passed through clouds of dust thick enough to cause a snowball Earth^{ref1, ref2}. It is possible that 2 such ultracold episodes, 600 million and 750 million years ago, might have been triggered in this way. Snowball Earth events are much more severe than normal ice ages : they occur through a runaway process in which growing ice sheets reflect ever more sunlight back into space, resulting in further cooling and more ice. Eventually, the ice advances from the Poles virtually all the way to the Equator, trapping the planet in a deep freeze. There is strong evidence in the geological record that Earth may have iced over in this way several times during its history. Various causes have been proposed, but none is fully convincing : the dust trigger is more plausible. Our Galaxy contains many giant molecular clouds, which are huge clusters of molecules that can clump into dust grains. As the Solar System moves through the galaxy, it passes through such clouds roughly once every 100 million to 1 billion years. Dust particles reflect sunlight, but they let Earth's heat out into space. In other words, they act as the precise opposite of greenhouse gases, cooling the planet. Such a cooling effect was observed after the eruption of Mount Pinatubo in the Philippines in 1991, which scattered volcanic dust into the atmosphere. The researchers calculate that the cooling effect of a passage through a dense molecular cloud could be at least 2-3 times greater, sufficient to trigger snowball cooling. If the planet were already on the verge of an ice age, even a molecular cloud of modest density could push it over the edge a larger freeze. The snowball Earth could then persist for about 10 million years, much longer than it would take the Solar System to cross a typical molecular cloud. The ice would thaw only when enough greenhouse gases from volcanoes had built up in the atmosphere. There could be a detectable geological signature of such an event. Interstellar dust is enriched in the isotope uranium-235, relative to its natural abundance on Earth. This dust would gradually settle out of the atmosphere and find its way into sedimentary rocks laid down at the time of the snowball freeze. Some doubt that such evidence, if it were to be found, would be conclusive, and do not see how an extraterrestrial trigger for the cooling can explain the apparent timing of such events. Why would you get two of them close together (600 and 750 million years ago), and then nothing?

Web resources : American Geophysical Union (AGU)
• 'northern lights' / auroraborealis : the researchers had thought they would need statistics to pick out any effect from the radio waves that targeted the aurora borealis on 10 March 2004. In fact, the sparkles were visible to the naked eye^ref. They used a 960-kilowatt radio transmitter at the High Frequency Active Auroral Research Program (HAARP) facility near Gakona, Alaska. The transmitter is twice as powerful as the BBC's biggest radio masts in Britain. The speckles of light form in the ionosphere, the layer of charged particles that begins about 50 km above the Earth and reflects radio waves around the globe. The ionosphere is filled with electrons streaming from the Sun. Most of these are deflected around the Earth's magnetic field. But some ride along magnetic-field lines into the upper atmosphere around the poles. Variations in electric fields in the polar atmosphere accelerate the electrons, which collide with molecules of oxygen and nitrogen in the air, making them glow and forming the aurora. Scientists do not know what causes this acceleration : some argue that a steady electrical field is responsible, as if different atmospheric layers were 2 terminals of a battery. Other says that waves in the ionosphere's electric field wash the electrons back and forth, boosting their energy every time they change direction. Pedersen and Gerken's finding supports the latter idea. HAARP's radio waves make the electrons bob like boats on the sea, showing that these waves could be enough to produce aurora. Some think that it may be possible to generate the speckles of light without an aurora present
• atmospheric sprites, the mysterious lights that dance above thunderclouds, have dazzled scientists with their sheer speed. Newly captured high-speed video footage shows the strange sparks shooting across the sky at > 1,600 km/s. Sprites were first captured on video by accident in 1989, and have subsequently been studied from above by NASA's Atlantis, Columbia and Discovery space shuttles. Although quite common, little is known about them because they last for mere milliseconds, making it difficult to measure how fast they move, or even where they go. Previous videos have either been unable to resolve the sprites' features, or have operated too slowly to catch more than a single frame of bright light. The first high-speed observations of sprites reveal details of their structure. The researchers watched sprites over New Mexico in July and August 2004, using a camera that shot 1,000 frames per second, allowing them to see how the sprites evolved from millisecond to millisecond. Some sprites are made of long chains of bright beads, each as small as 10 m across, separated by dark patches. Others appear to be continuous 'streamers' that taper to a fine point just a few metres across. Scientists think that the sprites' light is produced when fast-moving electrons hit nitrogen molecules in the air. These electrons come from the Earth's ionosphere, a layer of charged particles in the upper atmosphere > 60 km above the Earth's surface. The sprites usually appear during thunderstorms. When a thundercloud loses its electrical charge to Earth through a bolt of lightning, it leaves the cloud tops with relatively few electrons This sets up an enormous voltage between the cloud and the ionosphere, accelerating electrons that subsequently crash into molecules in the air. Some of the sprite features that the team saw only lasted for one frame, says Inan, which means that some aspects of the flashes are presumably still being missed. The team is now planning observations for this July with a high-resolution camera that takes about 10,000 frames per second. At this rate, the camera would only miss the evolution of the sprite if it raced across the 2.5-km field of view at better than 30,000 km/s, 10% of the speed of light^ref.
• Moon (diameter : 2,100 miles) : Small Missions for Advanced Research in Technology (SMART-1), launched by the European Space Agency (ESA) way back on 27 September 2003 (Europe's first Moon mission), went into orbit around the Moon on 15 Nov 2004. In January 2005, the craft began the first comprehensive X-ray survey of the Moon's surface, giving scientists clues about its composition and age. The size of a domestic washing machine, SMART-1 uses an innovative propulsion system that wafts the craft along on a breath of gas. It carries solar panels that convert the Sun's light into electricity, which is used to strip electrons away from atoms of xenon. This generates charged ions that are accelerated through a magnetic field and ejected from the rear of the spacecraft, producing a gentle thrust equivalent to the weight of 2 pennies resting on the palm of your hand. This is the first time ever that a probe has used ion propulsion to escape from the Earth. Conventional spacecraft engines rely on chemical reactions to generate gas, which pushes the craft forwards as it squeezes out of the engine, in the same way as a deflating party balloon will fly across a room. But in space, mass is money. Whereas chemical engines must carry 2 fuel substances to react together (often hydrogen and oxygen), SMART-1's ion drive carries only xenon, making it lighter and cheaper. The success of SMART-1 in reaching the Moon has proved that future spacecraft could use the same engines to get to Mercury and Mars. SMART-1 still has plenty of science to do during the 2 years it will spend orbiting the Moon. Its Demonstration Compact Imaging X-ray Spectrometer (D-CIXS) will make a chemical map of the lunar surface that should reveal whether the Moon was once part of the Earth. Many scientists believe that the Moon was formed after a gigantic collision between a Mars-sized object and the Earth about 4.6 billion years ago. Comparing the ratios of different chemical elements on the Moon and Earth could confirm this theory. SMART-1 also carries a high-resolution camera that will photograph potential landing sites for future robotic or even human explorers. And it will search for ice in the craters at the Moon's south pole, which haven't seen the Sun for billions of years, using an infrared spectrometer : this ice would be a vital resource for a manned lunar base. The 110-million (US$85-million) craft weighs just 370 kg, and took many spiralling orbits around the Earth to build up enough speed to reach the Moon. Its epic 80-million-kilometre journey has taken 13 months, compared with the 4 days taken to cover 400,000 kilometres by Apollo 11 during the first Moon landing mission. It entered a wide orbit around the Moon on 15 November 2004 after a 13-month journey. The engines have pushed SMART-1 in ever-decreasing loops around the Moon to bring it to 1,000 kilometres from the surface. The Asteroid-Moon Micro-Imager Experiment (AMIE) by Space-X (a company in Neuchâtel, Switzerland), which weighs just 450 grams, started taking pictures on 29 December and could identify potential landing sites for robotic or manned landings. Measuring the shadows around the craters will help scientists to work out the height of the crater rims. The probe also carries instruments that will map the chemicals on the lunar surface. Scientists hope these will reveal more about whether, as most think, the Moon was created > 3 billion years ago during a collision between another object and the Earth. An infrared spectrometer will hunt for ice deposits in the shadowy interiors of the Moon's deeper craters. The ion drive has been switched off since 12 Jan 2005 while scientists test SMART-1's instruments and make a medium-resolution survey of the Moon. When the engine is fired up again on 9 Feb, it will bring the probe to just 300 km above the surface. 5 months of scientific investigation will begin on 28 Feb. Pictures captured by an orbiting spacecraft have revealed that the Moon is being heavily eroded. Images of the lunar surface reveal deep cracks and holes that are slowly but surely releasing gas and dust into space. If the process continues, the Moon could eventually crumble away to nothing. Researchers are not yet certain what is causing the erosion : bacteria left behind by the Apollo Moon landings of the 1960s and 1970s may be responsible. These earthly bacteria, exposed to intense UV radiation on the lunar surface, could have acquired mutations that allow them to digest Moon rock. If those guys didn't wipe their feet when they stepped off the craft then, yes, there could be bugs up there eating the rock and after 3 decades there must be tonnes of them. Tycho crater, the youngest large-impact crater on the Moon's nearside, is particularly badly affected. The erosion has already revealed a large slab of jet-black rock deep in the crater, which has unusual magnetic properties. Recriminations are already brewing over why astronomers didn't spot the problem earlier. Amateurs on the ground have reported, on an almost monthly basis, that the light reflected from the Moon shows a dimming pattern: perhaps a sign that its weathered surface was becoming less reflective. One thing on which experts agree is that the Moon's disintegration would be a disaster, as tides on Earth would effectively stop : fish and ecosystems might totally be affected too. But others are seeing a positive side : without tides, there would be no need to upgrade London's flood defences for the next 2 centuries. As it is, if you live on the River Thames flood plain, the Moon is your enemy. John Koenig, director of Moonbase Alpha, a US project to establish a habitable colony on the Moon, insists that there is absolutely nothing to worry about. The images of the Moon were captured on 1 April by the Floating Optical Orbital Lens, as part of a multinational effort to photograph the Apollo landing sites. The mission aims to prove, once and for all and at fantastic expense, that the NASA astronauts really did go there.

How do you fancy winning a cool 250,000 dollars? That's the prize on offer for the astronomical alchemist who can create breathable oxygen from moondust. The competition, unveiled this week by NASA and the Florida Space Research Institute, is an attempt to stimulate research into technologies that might help humans to colonize other worlds. Although the prize won't quite allow the winner to breathe easily for life, the organizers hope that the hefty sum will tempt some talented chemical engineers. The rules are simple. Entrants must build a device, within certain weight and power limits, that can extract at least 5 kilograms of oxygen from a sample of volcanic ash (a substitute for lunar soil) in the space of 8 hours. The first team to build and demonstrate such a gadget before 1 June 2008 will claim the cash. The challenge is called MoonROx, for Moon Regolith Oxygen (the regolith being the layer of loose rubble on a planet or moon's surface). It is the latest in NASA's Centennial Challenges series. Other prizes up for grabs include an award for designing an efficient 'space elevator' for ferrying satellites quickly into orbit. Obviously, a sustainable source of oxygen is an essential if humankind is to realize US President George W. Bush's much-publicized vision of building a manned base on the Moon. And where better to get it than from the Moon itself? The use of resources on other worlds is a key element of the vision for space exploration. This challenge will reach out to inventors who can help us to achieve the vision sooner. The successful device will need to wrestle oxygen atoms from the silica and other minerals that form the majority of volcanic and lunar rock. Heating is unlikely to work, as volcanic rocks have already been forged in the Earth's fiery mantle, so competition entrants may consider using an electric current to separate negatively charged oxygen from the positive ions to which it is bound. The idea of offering cash prizes to spur space research has proved fruitful in the past. In October 2004, the crew behind SpaceShipOne scooped a $10-million booty from the X-Prize Foundation after it became the first privately built craft to complete 2 successful journeys beyond Earth's atmosphere. NASA is keenly following suit in its devotion to prize-led research. Indeed, those with an eye for history will note that NASA arguably owes its very existence to prize competitions, albeit ones from across the pond. In 1914, Albert F. Zahm, head of the Smithsonian aeronautical laboratory, noted with alarm the difference between the vitality of Europe's prize-sponsored aviation research and the USA own apathetic efforts. His comments led to the formation of the National Advisory Committee for Aeronautics, which later became NASA.
The Moon's soil preserves gases from the ancient Earth's atmosphere, say scientists who have studied results from the Apollo missions. The discovery hints that our planet's magnetic field switched on about 3.9 billion years ago. This in turn points to when life began on Earth, as the magnetic field protects us from a hail of DNA-damaging particles from space. Although the Earth formed some 4.5 billion years ago, current theories suggest that its magnetic field only kicked in after its core cooled. But no one knows exactly when this was, and researchers have been short on evidence. Minoru Ozima, a geochemist at the University of Tokyo, Japan, and his colleagues came up with a new approach to the question after looking at the data from soil samples brought back by astronauts in the 1970s. Moon soils contain traces of volatile elements such as nitrogen and argon. Scientists have long assumed that blasts of solar wind, flowing from the Sun's upper atmosphere, drilled these atoms into the soil. But there's a problem with this theory. Moon dust contains a very different ratio of two types of nitrogen, called nitrogen-14 and nitrogen-15, compared with the solar wind, explains Ozima. The ratio also varies from one grain of lunar soil to the next. Some of the Moon's nitrogen must have come from elsewhere. Ozima's team now argues that some of the nitrogen came from the Earth before it got its magnetic shield. Energetic cosmic particles would have whacked into the atmosphere, kicking some charged nitrogen atoms into space. Some of this nitrogen, which is richer in nitrogen-15 than the solar wind, would have wound up on the Moon. This source would have been more sporadic that the flood of nitrogen in the solar wind. That could explain why the isotopes are spread so unevenly across the Moon^ref. The team used computer models to work out how much nitrogen would have flown from the pre-magnetic Earth to the Moon. Then, by calculating how long the soil must have been sucking up nitrogen to attain its current isotopic ratio, they speculate that the Earth's magnetic field must have been either very weak or non-existent before about 3.9 billion years ago. Life is thought to have begun on Earth at least 3.5 billion years ago, according to microorganism fossils found in Australia. This would mean that life probably established itself quite quickly after the magnetic shield was in place. But pinning down exactly when the magnetic field turned on is tricky. It's very difficult to date lunar soil. This makes it difficult to determine exactly when the flow of nitrogen from the Earth stopped.  To verify Ozima's idea, lunar soil samples would have to be collected from the far side of the Moon for comparison. This hemisphere has probably always faced away from the Earth and so would never have been exposed to Earthly nitrogen. The Moon is thought by some to be a chunk of the early Earth chipped off in a collision with another body, but lunar soils should carry no trace of the earthly atmosphere. Any volatile gases on the soil grains would have evaporated long ago. Marty, who discovered the unusual distribution of nitrogen isotopes in lunar soil^ref, thinks the nitrogen came from a mixture of the solar wind, the Earth, and interplanetary dust. Untangling the 3 sources will be hard. But it could be helped by results from the Genesis spacecraft, which recently brought back samples of the solar wind.
NASA will spend US$104 billion to put humans back on the Moon by 2018. The first trip will send 4 astronauts to the lunar surface for a 7-day visit. That's much more ambitious than previous Apollo missions, during which 2 astronauts spent up to 3 days on the Moon. Although President George W. Bush outlined his 'Vision for Space Exploration' on 14 January 2004 in very broad terms, this study pins down how NASA will actually make the vision work on a realistic budget. Observers were most interested in the details revealed today for the new Crew Exploration Vehicle (CEV), which will be NASA's flagship once the Shuttle fleet retires in 2010. 2 aerospace consortia are working on proposals for this craft: Lockheed Martin Corporation lead one group, and the Northrop Grumman Corporation and Boeing head the other. Both teams will now tweak their early CEV designs to fit the detailed requirements unveiled by NASA. A final design will be chosen in early 2006. The CEV will look like a larger version of the Apollo craft, with a cone-shaped command module that will carry astronauts safely back to Earth using parachutes, rather than gliding in like the shuttle. It will sport solar panels for power while it is in space, and its engines will burn a mixture of liquid methane and liquid oxygen. Previous craft have burned other liquid fuels, but experts hope that methane and oxygen might one day be harvested from other worlds or moons for refuelling. Each craft should be able to make 5-10 trips before being retired, and they should be abut ten times safer than the space shuttle system. This is because the CEV will sit on top of a modified solid rocket booster, keeping the astronauts well out of the way of any falling debris. It will also boast an 'escape tower' that should allow the crew to bail out in the event of a launch failure. The craft should be ready by 2012, and will initially ferry up to six astronauts to and from the International Space Station. An unmanned version of the CEV could also be used to deliver cargo. But getting to the Moon will be slightly more complicated. NASA plans to first haul a heavy load of a lunar lander and accompanying rocket into orbit around the Earth. This requires them to start working on new engines capable of hauling this 125 tonne load. Astronauts would then use the lighter CEV to get up to the lunar lander, and use the rocket to cart them to the Moon. Then, as in the Apollo missions, they would leave the CEV to make the descent to the surface. After their week's stay, astronauts would then return to the CEV for their journey home to Earth. The mission plan aims to leave as much equipment on the lunar surface as possible, to help build future Moon bases. It also allows access to anywhere on the Moon, unlike the Apollo missions that were restricted to equatorial regions. This means that astronauts could explore the Moon's poles, where water ice probably nestles in shadowed craters. Exploiting the Moon's natural resources is essential if NASA is to have a permanently manned base there. Once the programme is up and running, 2 Moon mission will occur each year. The marked similarities between the missions demonstrate that by and large the Apollo folk got it right. The project does not require any extra cash beyond the normal NASA budget. "This is not about taking money from the science programme for human spaceflight.
Web resources :
• Google Moon
• Swedish Space Corporation's SMART-1 mission page
• Mars (1.52 AU from Sun) : on 27 August 2003 the red planet was < 56 million kilometres from Earth, the closest it's been for 60,000 years. It was early summer in the martian southern hemisphere. Towards us is its evaporating white south polar cap of dry ice - solid CO₂ - and protruding mountain ranges. Scientists believe that the martian atmosphere must once have been thick with CO₂, a greenhouse gas that would have kept the young planet warm enough for liquid water to carve its mark so clearly on the landscape. Some of this CO₂should have been trapped in tell-tale traces of carbonate minerals such as siderite (iron carbonate) that solidified from the oceans. Geologists have seen this happening on Earth, but NASA's orbiting craft, the Mars Global Surveyor and Mars Odyssey, have found very little carbonate on the red planet's surface. The answer is that the oceans were acidic enough to stop any siderite solidifying. If Mars's oceans were richly salted with iron and sulphate ions, the seas' pH would have dropped to around 6.2; similar to some tap water, but not quite as acidic as vinegar. Earth's oceans today have a pH of about 8. As the oceans receded, any dissolved CO₂ would have been lost back into the atmosphere, and eventually stripped away from the planet by the harsh stream of solar particles bombarding the planet^ref. NASA's exploration rover Opportunity^{ref1, ref2, ref3, ref4, ref5, ref6, ref7, ref8, ref9, ref10, ref11, ref12, ref13} recently found large quantities of sulphate minerals such as jarosite on Mars. Today's martian atmosphere is at < 1/100 the pressure of Earth's atmosphere. But 4 billion years ago, volcanic eruptions would have flooded Mars with SO₂ and CO₂, to create an atmosphere with 4 times the pressure of Earth's. This atmosphere supplied a steady drizzle of acid rain, which dissolved iron, magnesium and other minerals as it trickled into the oceans, putting roughly a gram of iron in every 22 litres of seawater. The briny seas would also have contained the same concentration of sulphate that is formed by dissolving a teaspoon of Epsom salts (magnesium sulphate) in about 5 litres of water. We know from the geological history that there has been plenty of volcanism on Mars, so these concentrations are reasonable if there was also a huge CO₂ reservoir. The resulting scenario is very exciting because the cycle allows long residence times for CO₂ in the atmosphere. Basically, the lack of carbonates in the martian surface could have helped to keep Mars warm for longer. A warm planet is good news for the prospect that life once existed there. The team's martian model shares much of its chemistry with parts of the Rio Tinto, in south-west Spain. This acidic river, in which high concentrations of iron and sulphur are dissolved, teems with living creatures including bacteria, yeast and fungi. Meanwhile, Mars' proximity is giving researchers a chance to save fuel. A flotilla of small, cheap landers - Europe's Mars Express, NASA's twin Mars Exploration Rovers, and Japan's Nozomi - left Earth earlier this year to race to the red planet. In December and January they will parachute onto its surface to take samples and pictures. Similar Mars missions will continue to depart every two years over the next decade. You only need to look at the Pathfinder images of the martian surface and you can imagine walking around there. Water ice has been found metres below Mars's parched surface by orbiting satellites, hinting that life may once have existed there, or may still lurk in deep underground crevices. Future missions will search for underground water pockets using seismic radar. Infrared surface scans failed to find vast limestone deposits that might signify a dried ocean or lakebed, but did detect tiny amounts of carbonates, which hint at water. Mars is also a good laboratory for understanding the Earth's climate, with its 24-hour day and similar land surface area. The wobble of Earth's spin axis is thought to explain the timing of ice ages, but it is small and hard to measure. Mars' wobble is much more pronounced. The red planet's wider climate variations should be etched in its rock layers, as might the climatic effects of subtle changes, over hundreds of millions of years, of its elliptical orbit around the Sun. Mars orbits the Sun more slowly than Earth, lapping it every 26 months. But Mars' orbit is more elliptical, and other planets and asteroids tug both bodies slightly off their paths. So once in a while, they come unusually close together. Detailed calculations of the Solar System's gravity landscape predict a closer approach in 2287. Mars' atmosphere is almost entirely composed of toxic CO₂, and it has only 1/20 of the surface pressure on Earth. Seasons oscillate wildly - a third of the tenuous atmosphere sloshes from north to south as it condenses in winter to form white polar caps, and then vaporizes in summer. Summer dust storms rage over hundreds of kilometres. Lacking much air or any protective magnetic field, cosmic rays burn down from space, sterilizing the surface of the planet. NASA's Spirit probe has started beaming home snapshots from Mars on Jan 4, 2003 : spirit has landed in a huge crater called the Gusev Crater, which planetary scientists think might once have held a lake. A channel resembling a dry river valley leads into Gusev, and may have been carved by flowing water billions of years ago. Its sister probe, Opportunity, is now approaching Mars at the end of its seven-month flight from Cape Canaveral in Florida, and is scheduled to touch down on the opposite side of the planet on 24 January. NASA last landed a spacecraft on Mars in 1997, when the Sojourner rover of the Pathfinder mission explored the planet's surface. The current success of Spirit provides some welcome new year cheer after the suspected demise of Beagle 2, a Mars lander mission conducted by the European Space Agency (ESA). Beagle 2 was carried to Mars on board the Mars Express spacecraft, which is now orbiting the planet. Beagle 2 seems to have touched down as planned on Christmas Day, but since then it has remained silent, failing to communicate with its mother ship. Scientists are still scanning Mars in the hope of picking up Beagle 2's signature tune, but that hope is fading. Mars Express is now adjusting its orbit in preparation for scanning the martian surface from on high. Its final orbit will bring it to within 300 km of the surface, from where it will also search for signs of frozen water beneath the martian soil. Vladimir Krasnopolsky, an atmospheric scientist from the Catholic University of America in Washington DC used the Canada-France-Hawaii Telescope on top of Mauna Kea in Hawaii to detect minute traces of methane in the red planet's atmosphere; they found levels of 10 ppb. This matches other researchers' estimates, and suggests that methane is being continually released from the surface. No physical process can account for that amount of methane : the gas must come from a biological source, and assuming martian methanogenic bacteria have similar biochemistry to terrestrial ones, there could be 20 tonnes of methanogenic bacteria currently living on Mars. If they were evenly distributed around the planet in a warm layer about 100 metres thick, each bug would have roughly 10 cm³ of space to itself. But Krasnopolsky argues that the martians are probably concentrated in just a handful of oases, which would explain why NASA's Viking landers missed any signs of organic chemistry on Mars in 1975 and 1976. An organized martian hunt would be difficult as methane mixes into the atmosphere too quickly for us to follow it to a precise location. Mars Express reveals that patches of both methane and water vapour come from 3 distinct areas of Mars: Arabia Terra, Elysium Planum and Arcadia-Memnonia. These locations all have stores of ice just below the surface, which might house a common source of the 2 gases, but scientists are still unsure whether that source is biological or geological. Other researchers have found organisms living > 500 metres below the Canadian permafrost. A cracked rock called Escher is helping NASA scientists reconstruct the history of water on Mars : the crater currently being explored by the Opportunity rover may have been shaped by a second watery episode long after the wet period when the rocks first formed. The flat rock carries a network of fissures that looks like cracked mud at the bottom of a dried up riverbed. Long after the sedimentary rocks in the area had formed, water may have welled up from underground to form a small lake within the stadium-sized Endurance crater. As the surface dried out again, the rock slowly cracked apart under the weak martian Sun. Alternatively, climate changes on Mars could have melted and frozen water within the rock, which opened out the channels over thousands of years. However, the scientists cannot yet rule out the possibility that the rock was cracked during the impact that formed the crater. They plan to send the rover to look for a crust of water-soluble minerals on a nearby rock called Wopmay, which would strengthen the case for wet conditions after the crater formed. The history of this area would then become much clearer. Large sheets of sedimentary rocks formed underwater billions of years ago, before a meteorite impact dug an enormous hole in the dry surface. Later, the martian climate must have again been warm enough to see liquid water - perhaps fleetingly - in the crater. NASA mission managers are now planning Opportunity's escape route out of Endurance crater. The rover should leave within the next 2 to 4 weeks, and then trundle about 200 metres to the heat shield that was ejected from the descent module as it delivered Opportunity safely to the planet's surface. This should provide the first direct evidence about the performance of the heat shield, which will be vital information for future Mars missions. Now that the rovers have made it through the darkest days of the martian winter, their solar energy supply will increase through the coming 2005 year. Although the mission has officially been extended for another 6 months, mission scientists hope that the rugged robot geologists could last even longer. The Mars Express spacecraft has returned stunning images of mountains and valleys that show signs of past volcanic activity, and suggest that glaciers once shaped the red planet's surface. Meanwhile Beagle 2 is still making waves despite having made no contact with its handlers since separating from its mother ship on 19 December 2003. The pictures from Mars Express show the western end of the Valles Marineris canyon system, which stretches for about 4,000 kilometres close to the martian equator. In places, the main canyon is 10 km deep, > 6 times as deep as the Grand Canyon in Arizona. Mars Express's High Resolution Stereo Camera (HRSC) has now photographed this area in more detail than ever before, picking out features as small as 50 metres across. The images are showing us a lot more evidence for recent water activity, and probably recent ice deposits, than I'd previously thought. Larger features, such as U-shaped valleys punctuated by hillocks of rubble, indicate that glaciers may once have gouged their way through the canyons. The pictures also show that the canyon floors are covered in dark, layered material, which could be volcanic. Because the HRSC's stereovision provides 3D pictures, geologists can analyse these exposed rock formations to unpick how the geology of the planet has changed over time. Mars may have been volcanically active very recently, perhaps as little as a million years ago. On November 3, 2004, Colin Pillinger, the space scientist from the Open University who was the driving force behind Beagle 2, announced the team's plans for a new lander that could fly on an ESA mission in 2009 to look for life on Mars. In particular, the team proposes installing a communication system that would allow the craft to keep in touch directly with Earth during its descent through the martian atmosphere. It would also use pillow-like airbags to cushion its landing. As ESA did not ask the team to prepare its new proposal, there is no guarantee that the project, named Beagle 2: Evolution, will make it off the drawing board. A plan to keep parts of the red planet in their pristine state could see seven areas turned into 'planetary parks', regulated just like national parks here on Earth. Although scientists have found no life on Mars, many national parks on Earth are protected partly for their geological interest and natural beauty, such as the Grand Canyon and Antarctica. And if Mars has simple microbial life, there are even greater reasons for establishing planetary parks - to protect that life from human destruction. We've already crashed unmanned spacecraft there - Mars Polar Lander and possibly Beagle 2 - so there's already an environmental issue. 7 different areas contain representative features of the martian landscape. The Polar Park would protect the planet's ice cap for biological studies, while Olympus Park would encompass the Solar System's largest volcano, Olympus Mons, to prevent future mountaineers despoiling it, as has happened with Mount Everest. Others parks would cover desert areas, impressive meteorite craters and the landing sites of the Viking 1 and Mars Pathfinder spacecraft. This map of Mars highlights 6 of the proposed conservation sites – the Polar Park is not shown :


Other scientists have already proposed making the Apollo 11 landing site a world heritage site, but no one has really suggested putting this together into a single parks system. The system could work just as well on the Moon. The UN Office for Outer Space Affairs (OOSA) in Vienna, Austria, would be best placed to administer the parks. But the sole purpose of planetary protection regulations that limit the number of spores allowed on a Mars lander is to stop experiments looking for life becoming contaminated. However, establishing the parks would present an enormous challenge for international law. Many spacefaring nations such as the United States, Russia and China have not even signed up to the existing UN Outer Space Treaty, which seeks to make outer space "the province of all mankind". But if a planetary parks system were in place, it would free up the rest of the planet for exploitation and claim-staking, which might encourage these nations to sign up to the system.
The Mars rover Opportunity may have found an iron meteorite. NASA scientists believe it probably came from the core of a large asteroid, which broke up when it crashed into the red planet. Opportunity spotted the odd-looking rock on 10 January, the rover's 345th martian day on the planet. The rover had previously spent 6 months inside Endurance crater, studying the layered rock outcrops there. After carefully picking its way out of the crater, Opportunity trundled over to where its protective heat shield had landed after being ejected during the rover's descent. Mission engineers wanted to get a good look at the shield, now in 2 fragments, to see how it had stood up to the battering on the way down. And right there next to the heat shield is a little rock which they imaginatively call 'Shield Rock'. Infrared scans of the rock suggest that it is actually made of metal. They believe they've found an iron meteorite. You'd expect there to be meteorites on Mars, but the chance of actually bumping into one is incredible. Meteorites are chunks of Solar System debris that manage to reach a planet's surface without completely burning up in the atmosphere. Most originate from the break-up of asteroids. Outer parts of the asteroid usually produce stony meteorites, but iron meteorites, which also contain traces of nickel and other metals, are thought to come from the cores of larger asteroids. When such asteroids formed, the metal stayed molten long enough to accumulate at the core, separating from the less dense minerals that remained in the outer portions of the asteroid. Meteorites are prized by scientists who use them to work out the age and nature of their parent bodies, which helps to build a picture of what the solar system was like at the time when the asteroids first formed. Opportunity will use various instruments over the next few days to determine the rock's exact composition, but its investigation of the heat-shield fragment is going less well. The rover is hampered by the fact that the shield seems to have turned inside out when it crashed into Mars. The outer thermal protection layer is now relatively inaccessible, but Opportunity has been using its microscopic imager to take a close look at the debris. With luck, these observations may help to improve our ability to deliver future vehicles to the surface of other planets.
Although the HRSC is producing a continuous stream of data from the red planet, one of Mars Express's most useful tools remains firmly stowed and will not be used before March 2005. The Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS), the craft's 40-metre-long radar antenna, has the potential to detect underground stores of water a few kilometres below the martian surface. Mission scientists are worried it might damage the craft when it swings into position. They are now performing extra simulations to determine whether it is safe to deploy the instrument. The radar stowed on board the European Space Agency's Mars Express orbiter will finally be unfolded in early May 2005. The MARSIS will look for traces of water ice beneath the martian surface, and could potentially detect reservoirs up to 5 km underground. Mars Express arrived in orbit around the red planet on 25 December 2003, and MARSIS was supposed to have been deployed in April 2004. But computer simulations by the instrument's manufacturers, Astro Aerospace of Carpinteria, California, showed that when the radar's long booms swing into position they might hit other instruments or fatally destabilize the craft. MARSIS consists of a pair of 20 m hollow fibreglass cylinders, each 2.5 cm in diameter, and a 7 m boom. Wires inside the tubes will generate radio waves that penetrate planet's crust before reflecting back to a receiver onboard Mars Express. The tubes are folded into a concertina that will automatically stretch out when its container is opened. The boom system was created by NASA's Jet Propulsion Laboratory in Pasadena, California, which has been running a full assessment of the risks of unfolding MARSIS. An independent engineering review board of the ESA and industry experts finally decided on 25 Jan 2005 that the tubes posed little threat to Mars Express, and the instrument should be unfurled in the first week of May. If all goes to plan, MARSIS will probe the planet until at least 30 Nov, the proposed end date for the Mars Express mission. The MARSIS results could also direct future robotic and manned missions to the surface : if there are vast reservoirs of ice, that's the sort of place we have to look for life. MARSIS is the first experiment designed to find water several kilometres below the martian surface. But its deployment has been on hold since April 2004, about 4 months after Mars Express arrived at the red planet, because mission engineers feared that its radio antennae might hit other instruments on the craft when they swung into position. After careful computer simulations of the manoeuvre, the first of the radio booms was finally unfolded from the ESA craft on 4 May. But 3 days later, flight engineers at the European Space Operations Centre in Darmstadt, Germany, realized that one of the 13 segments had locked into position at an angle, putting a kink in the antenna. ESA has delayed unfurling a second boom until they work out exactly what has gone wrong. Until at least 2 of MARSIS's 3 booms are correctly in place, the experiment is useless. Scientists hope that MARSIS will eventually use 2 20-metre-long antennae to beam radio waves at Mars. Most will bounce off the surface, but some should penetrate several kilometres deeper, and reflect off any underground layers of liquid water or ice. Although the 2 booms alone can detect these reflected waves, a third, 7-metre-long boom is intended to pinpoint exactly where the waves are reflected from. We had lots of evidence of ancient water on Mars, and good evidence of ice, but no ability to detect buried liquid water before now. The booms have been packed, concertina fashion, since the probe left Earth in June 2003. It's too early to say whether keeping the boom folded for a year longer than expected has caused this problem, but it is the only variable we cannot simulate here on Earth. We have run a number of simulations but this particular failure case has never come up. They could open the second boom now. But if that too locks into position at an angle, it could fatally destabilize the whole craft. At the moment, the risk seems too great to try that, he adds. So if ESA engineers cannot find a way to unlock the jammed hinge, the experiment may have to be abandoned. The first MARSIS radar boom successfully locked into place on May 11. Mission engineers guessed that the problem might have been caused by prolonged storage in the deep cold of space, which may have badly affected materials in the folded antenna. So they turned the Mars Express spacecraft around on 10 May, allowing the Sun to heat up the cold side of the boom for 1 hour. This appears to have expanded the joint enough to let the antenna pop into position. The deployment of the other 2 booms should continue in a few weeks.
If life exists on the surface of Mars, it has not encountered liquid water for several billion years. It seems that the European Space Agency's orbiter, Mars Express, has found no evidence of the necessary greenhouse effect. The result comes from Mars Express's OMEGA instrument, which analyses visible and infrared light from the planet to reveal the chemical composition of the surface. Mars Express has previously taken photographs of deep channels that suggest icy glaciers moved across the planet's surface just millions of years ago. But the question is whether the past conditions on Mars allowed water to be in liquid form. Terrestrial experience tells us that all life needs water, so scientists have been eagerly hunting for clues that might suggest Mars was once warmer and wetter at some point in its history of 4.5 billion years. Early Mars could have kept warm with a blanket of CO₂ that would have absorbed and re-radiated heat lost from the surface. Such a greenhouse effect would have raised the temperature enough for water ice to melt. But everything points to the fact that Mars lost its atmosphere early on. After a global survey, Mars Express has found none of the carbonate minerals that would form under a dense CO₂ atmosphere. This makes it unlikely that the planet ever experienced significant greenhouse warming, contrary to some scientists' expectations. NASA's Mars Exploration Rovers, Spirit and Opportunity, have studied rock formations and mineral deposits that prove liquid water once flowed over the surface of Mars. But the exact timing of these aquatic events has remained elusive. Liquid water may have been common on the planet in its first billion years: but after that, if there was life, it disappeared or was blocked into niches. OMEGA, which stands for Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité (the Observatory for Mineralogy, Water, Ice, and Activity), also looked for sulphate minerals, which tend to form in water. Large deposits of sulphates at the north pole, as well around regions known as the Valles Marineris and Terra Meridian, provide the most comprehensive record yet of water-driven activity over large swaths of Mars. And the craft has finally given researchers concrete evidence that the frosty poles are dominated by water ice. Astronomers knew that Mars possessed polar ice caps, and measurements by NASA's Mars Global Surveyor craft found that the caps were a mixture of water and CO₂ ices. But it now seems that the south pole has only a thin veneer of frozen carbon dioxide that covers huge deposits of water ice
The Mars Express spacecraft, currently orbiting the red planet, has taken snapshots of what appears to be a dust-covered frozen sea. The pictures, taken by the High Resolution Stereo Camera (HRSC) on board the European Space Agency's craft, show a flat plain close to Mars's equator that is covered with irregular blocky shapes. They look just like the rafts of fragmented sea ice that lie off the coast of Antarctica. The researchers think that the camera has snapped a sea that froze about 5 million years ago, and was then covered by volcanic dust. This suggests that pockets of liquid water have existed throughout Mars's geological history. This feature, roughly 3 km across, shows a rubble field pushed out from the right of a crater. This rubble looks like the piles of sea ice that form around islands in the Arctic and Antarctic. The ice-raft features were seen about 5° north of the equator in a region called Elysium, which contains several enormous martian volcanoes. In the past, parts of Elysium have been flooded with both lava and water from deep fissures called the Cerberus Fossae. These cracks go down several kilometres to a water-rich layer. Ancient floods of water have carved channels into the rock. But no one expected that any of the water would remain frozen on the planet's surface to this day. The atmosphere of Mars is so thin that ice should simply sublime, evaporating without melting in the equatorial sunlight. But the frozen sea is insulated by a layer of volcanic dust, through which water vapour escapes only very slowly. The ocean formed from water gushing out of the Cerberus Fossae and, as it started to freeze, floating pack ice broke up into rafts. These became covered in dust from volcanic eruptions in the region. While the entire sea froze solid, the ice between the rafts, which was unprotected by dust, sublimed to leave 'ice plateaus' surrounded by bare rock. The sparse cratering of this region shows that it cannot have formed > about 5 million years ago. Another, more mundane possibility is that the blocks now visible in the plains of Elysium are not ice at all, but rock formed from solidified lava. However, they do not look anything like lava features seen elsewhere on the planet.  The 'frozen sea' is a mere 45 m deep and 800 by 900 km in area: about as big and as deep as the North Sea off Britain's coast on Earth. The MARSIS radar detector on Mars Express, which is scheduled to be deployed in April or May, is designed to search for reservoirs of water on or below the Martian surface. But sadly its resolution is slightly too low to be able to confirm whether such thin sheets are actually made of ice. The area is likely to be a priority for future studies of Mars, because if there is a deep layer of liquid water below the Cerberus Fossae, life could still exist in it. Disgorged on to the surface in the floods that created a sea, the remains of such organisms might now lie frozen in the dust-covered ice. The European Space Agency is planning to send a lander mission to Mars at the end of the decade to look for life, and this icy area would make an ideal target.
Pictures of Mars's north pole have revealed a record of the planet's climate over the past 3 million years. The climate history is written in light and dark bands exposed on the sides of ice cliffs. Scientists now say that they can read these bands in the same way as climatologists on Earth interpret cores drilled from deep-sea sediments. Pictures from the Mars Orbiter Camera on board NASA's Mars Global Surveyor craft were combined with data from the craft's Mars Orbiter Laser Altimeter to pinpoint the precise separation of these bands to a resolution of just a few metres. The climate changes recorded in the bands seem to be driven by wobbles in the planet's orbit, something that planetary scientists have suggested could make the ice at the poles wax and wane, or even disappear altogether^ref. The north pole of Mars is covered with a thick cap of water ice, > 1,000 km wide and up to 3 km deep. Spiral patterns of deep troughs cut deep into the ice, in places exposing 800-m-high vertical cliffs. A banding pattern of light and dark layers recurs roughly every 30 metres through the ice, caused by a change in the planet's orbit that happens every 51,000 years, moving it slightly closer to or further from the Sun. The darker bands contain more dust, and relate to periods when Mars's northern hemisphere was getting more sunlight than the southern hemisphere. When this happens the atmosphere in the north warms, whipping up winds that carry dust to the north pole. The increase in sunlight also melts larger amounts of the polar ice than melt in a normal summer, so the dust becomes more concentrated in the uppermost layer of ice. Matching patterns were found in 10 different troughs across about 75% of the ice cap, proving that the layering was caused by a regional change and not just a local event. The banding pattern is missing from a 100-metre section of the ice that corresponds to a period between 0.5 million and 2 million years ago. That looks like strong evidence for an 'ice age' on Mars, when frozen material from the pole crept down towards the equator, like ice ages on Earth. Unlike the shorter cycle caused by orbital wobbles, this change was probably caused by a tilt of the planet's axis, which chilled the equator by moving it away from the Sun, but relatively warmed the north pole. The much increased melting at the pole meant that the layers were disturbed enough to break up the regular 51,000-year pattern. The 30-metre pattern resumes deeper into the ice, and indicates an 'interglacial period' between 2.1 million and 2.7 million years ago. Then, even earlier, the pattern disappears again, possibly corresponding to the end of another ice age between 3 million and 4 million years ago. The research should help to explain how Mars's polar ice caps change, and how they distribute water around the rest of the planet.
Web resources : Malin Space Science Systems (MSSS)
Formaldehyde has been found in the martian atmosphere, according to a senior scientist working with the Mars Express orbiter. If correct, the discovery provides strong evidence that Mars is either extremely geologically active, or harbouring colonies of microbial life. But many experts are not yet convinced. The claim comes from Vittorio Formisano, who is in charge of the Planetary Fourier Spectrometer on the European Space Agency's orbiter. The spectrometer analyses infrared light, whose frequencies carry the fingerprints of chemicals in the atmosphere. The most likely source of formaldehyde (CH₂O) is the oxidation of methane (CH₄), which has already been identified in the martian skies. So the presence of formaldehyde itself is not too surprising. Any oxidizing atmosphere such as Mars's that contains methane should also have formaldehyde. The truly eye-opening part is the sheer quantity of formaldehyde that Formisano claims to have found: about 10 to 20 times more than there is of methane. This means that estimates of martian methane production must be revised upwards substantially, as most of the gas is oxidized as soon as it comes out of the ground. If you consider formaldehyde as oxidized methane, then Mars is producing 2.5 million tonnes of methane a year : this is simply too much to be accounted for by any known geological process, so some other source (possibly life) must be involved. However, other planetary scientists say the planet alone could still be responsible. We don't know the intricacies of martian geochemistry. Formisano presented his results to a packed session of the Mars Express Science Conference at Noordwijk in the Netherlands on 24 February 2005. The discovery of martian methane in 2004 excited scientists, who said that there were 2 likely sources of the gas: active geological processes beneath the planet's surface or a population of methane-generating microbes. Because Mars was long thought to be a dead planet, devoid of both life and geothermal activity, either prospect came as a revelation. However, a molecule of methane can typically survive for about 350 years in the atmosphere before being broken down by the Sun's ultraviolet radiation. So the possibility remained that the gas could have been delivered to the planet by a colliding comet, or by an occasional release from an underground reservoir. Formaldehyde is far more unstable, surviving for just 7.5 hours or so before breaking apart. The majority of scientists agree that methane is the most likely precursor for formaldehyde on Mars, so this means that the planet's production of methane must be an ongoing, continuous process. The measurements are right on the borderline of the instrument's ability : infrared fingerprint of the formaldehyde in Mars's skies should match a laboratory sample of the gas, and the match is just not convincing. But Formisano argues that his martian spectrum tallies in 15 key places, which should be enough to convince anyone. Although rejected by Nature, the research will soon be published in the journal Planetary and Space Science. Formisano also announced at the conference that he has found traces of hydrogen fluoride (HF) and hydrogen bromide (HBr) in the atmosphere, which are probably produced when acids break down certain minerals in the soil. Many scientists believe that Mars once had briny, acidic seas that may have been conducive to life : an acidic environment still exists. On Earth, there are certain bacteria that prefer very acid conditions. He has found higher concentrations of methane directly above an area of Mars that seems to be covered in pack ice. This raises the tantalizing possibility of a microbial colony living beneath the surface. More convincing evidence for life is needed : continuous production of heavier hydrocarbons such as propane, which cannot come from geothermal processes, would be a key finding. Better still would be a skew in the ratio of carbon isotopes in the air, as produced by organisms on Earth. NASA and the European Space Agency are both planning Mars missions for the end of the decade that will look for precisely that.
One of the best chances for solving Mars's methane mystery may have been lost. The Planetary Fourier Spectrometer (PFS) on board the Mars Express orbiter seems to be broken, perhaps for good. The instrument's failure would be a blow for scientists who want to find out how the red planet is producing the methane that has been detected in recent years. Almost all the methane on Earth comes from some sort of biological source. As a methane molecule typically survives for only a few hundred years in the martian atmosphere, something must have been spewing it out recently, scientists reason. And this has fuelled hopes for discovering life on Mars. But scientists have recorded very different methane levels with different techniques. In 2004, the PFS found that methane averaged abut 10 parts per billion in Mars's atmosphere, suggesting that more than 100 tonnes of the gas is released from the surface each year. That same year, levels of 250 ppb were spotted using a telescope in Hawaii. In August 2005 he spotted levels of 44-63 ppb from a different part of the planet. To pin down the source of the gas, these disagreements need to be sorted out. One explanation might be that methane is venting intermittently from specific points on the surface. To check, researchers hope to take simultaneous readings of exactly the same place using both orbiting and earth-based instruments. But the chance to do this may now be lost : the spectrometer has been in trouble for 2 months, and various attempts to fix it have proven fruitless. There's still a chance it could be fixed, but if it cannot be fixed then the experiment will be stopped. The instrument stopped working some time in July. It's a problem with the vibration of the spacecraft. These vibrations have shown up in PFS data for the duration of the mission, although scientists have been able to filter out the effects to generate clean results. The vibrations are affecting a pendulum inside the instrument that helps to control the way it collects light. But team members are unclear about the severity of the problem. Vittorio Formisano of the Institute of Physics and Interplanetary Science in Rome, Italy, would not confirm that it is broken. Formisano is in charge of the instrument and says he is being kept busy working on it. This isn't the first trouble that Mars Express has had. The European Space Agency's craft had difficulty opening some radar booms needed for its water detection experiment in May, although these are now working well. And there have been controversies surrounding interpretation of data from the spectrometer. In February 2005 the PFS found large quantities of formaldehyde around Mars. This implied that millions of tonnes of methane were being released by the planet each year: much, much more than thought. Most scientists now agree that these claims about formaldehyde were incorrect.  Without nailing the methane numbers, it will be hard for all scientists to agree on a source for the gas. For now, many say it is probably due to heating of water and carbon dioxide with a mineral called olivine, rather than life. If the Mars Express methane instrument fails to provide further data, the next opportunity will be NASA's Mars Science Laboratory, due to blast off in 2009. This will not only measure trace levels of methane, but also check its isotopic make-up for signs of biological activity.
• moons :
• Phobos
• Deimos
Movies of dust-filled whirlwinds on Mars have been sent back by NASA's exploration rover, Spirit. The Mars Global Surveyor orbiting probe has seen these 'dust devils' before, but Spirit's close-ups reveal much more detail about the miniature tornados. This is the best look we've ever got of the wind effects on the martian surface as they are happening. The robot is currently in the Columbia Hills overlooking Gusev Crater, the vast plain where it landed 463 days ago. In March 2005, the rover accidentally snapped a handful of blurry dust devils with its navigation camera, but the images showed little detail. So the rover team told Spirit to take several series of 21 pictures, focusing on areas where dust devils were likely to be found. The pictures were taken about 20 seconds apart, on 15 and 18 April. The dust devils are caused by convection currents set up by the temperature difference between the sun-baked surface of Gusev Crater and the chilly air above. Tracking the devils reveals which way the wind blows on Mars, and how they contribute to larger dust storms, helping scientists to build up a detailed picture of martian weather. Spirit was actually hit by a dust devil in March, which helpfully swept clean its solar panels. Although dust build-up had reduced Spirit's power output by almost half, this spring-clean boosted the solar power back up to 93% of its original capacity. The rover is now trundling over to a rocky outcrop nicknamed Methuselah, so called because the team believe it to be extremely old. They plan to study the rock in detail over the weekend^{ref1, ref2}.
The methane in Mars's atmosphere could easily be produced by mineral chemistry, rather than life. That's the claim from a pair of geologists whose calculations suggest that some experts have been too quick to assume a bacterial source for the gas. When methane was found in the red planet's atmosphere in 2004^ref, scientists immediately realized that there must be a continuous or recent supply somewhere, because the average martian methane molecule is destroyed by sunlight after spending 340 years in the atmosphere. Could this gas be a whiff of life from methane-producing bacteria, scientists wondered. One team calculated that it would take just 20 tonnes of bacteria to generate the observed concentration of methane in the atmosphere^ref. But many geologists were sceptical, pointing out that minerals such as olivine can create methane in a process known as serpentinization. It could be serpentinization, but nobody had actually worked out how much olivine it would take : the process would consume about 80,000 tonnes of olivine each year. To spit out methane at the same rate over the planet's 4.5-billion-year lifetime would require a global, 50-cm-thick layer of the mineral, spread a few km below the planet's crust. That would be just one millionth of the mass of the planet. The calculation^ref, could swing the debate. When olivine is heated under pressure, it reacts with water and carbon dioxide to create methane, leaving the mineral serpentine behind. Geologists have calculated that the necessary conditions exist a few kilometres below Mars's surface. And we know that the red planet hosts some green olivine: the mineral has been found in martian meteorites, and has been spotted by both the Mars rover Opportunity and NASA's orbiting probe, Mars Global Surveyor^ref. The extent of one particular olivine field has been revised upwards by four times after an extensive analysis of data from NASA's Mars Odyssey orbiter^ref. It is now thought to be the size of Cuba. The rock looks as though it was forced to the surface during ancient volcanic activity, so even more olivine may lie beneath the surface. A crucial test of the serpentinization theory is whether the Mars rovers find serpentine. On the other hand, the measurement of carbon isotopes in the methane, slated for a Mars mission at the end of the decade, might prove that bacteria are the source. In the meantime, some scientists continue to debate whether there actually is any methane on the planet at all, and are holding out for further measurements.
Regular meteor showers occur when a planet approaches the orbit of a periodic comet — for example, the Leonid shower is evident around 17 November every year as Earth skims past the dusty trail of comet Tempel-Tuttle. Such showers are expected to occur on Mars as well, and on 7 March last year, the panoramic camera of Spirit, the Mars Exploration Rover, revealed a curious streak across the martian sky. Here we show that the timing and orientation of this streak, and the shape of its light curve, are consistent with the existence of a regular meteor shower associated with the comet Wiseman-Skiff, which could be characterized as martian Cepheids^ref.
After a long uphill hike, there's no better reward than the view from the summit. So it is understandable that the operators behind the Mars rover Spirit had their robot pause to survey the terrain after it reached the top of Husband Hill, even if the area does look remarkably similar to the area from which the rover just came. It's one of the best pictures Spirit has taken, because it contains a little bit of everything his team has been looking for on Mars. In the distance, a dust devil dances across the plain, and ridges of windblown sand lap at the rover's wheels. Nearby, rocks crusted with mineral grains carry clues to Mars's geological history. Perhaps more surprising than the view is the simple fact that Spirit made it to the top of the highest peak in the Columbia Hills formation. Spirit has been exploring the red planet for 582 martian days, or sols, and the rover just keeps on keeping on. This epic climb has taken > 1 year, and the robot shows no signs of flagging. Although its right front wheel is a little sticky, and the grinding tool has been completely worn down by too many hard, volcanic rocks, everything seems to be working OK. Initially slated to last just 90 days each on Mars, Spirit and its twin rover Opportunity have completed more than a thousand days of work between them. The mission's homepage now logs the rovers' progress in terms of 'sols past warranty'. The mission scientists spent the first nine months of the project at the Jet Propulsion Laboratory in Pasadena, California. But as the rovers refused to die, the scientists returned to their home universities in September 2004 to continue the campaign remotely. Arvidson has telephone meetings with his colleagues every day to plan the rovers' activities. Spirit has driven about 5 km since it touched down in Gusev Crater on 4 January 2004. For much of its mission it has been overshadowed by its twin Opportunity, which has found copious evidence of minerals shaped by water on the other side of the planet. But since beginning its climb into the Columbia Hills in June 2004, Spirit has found a much wider variety of rocks. Some contain minerals that probably formed in water, although "none of it shouts out that it was formed in a lake. Spirit will spend several weeks at the summit to measure how much the Sun's rays heat the slopes of distant hills, and how this drives Mars's windy weather. We're at this hilltop observatory now, so we can make some unique measurements. The rover is getting in position to take a full colour, 360° panorama photograph on 25 August, which should pick out other peaks in the Columbia Hills, along with the valleys and plains on either side. But what the scientists are most keen to get are the close-ups of rock and soil on the far side of the hill, rather than the long views. Once Spirit has picked its way down the southern flank of the hill, it will try to reach Home Plate, an area of layered rock more than a kilometre away. No one knows how much longer the rovers will last. Although they show no signs of flagging, they could give up at any moment. Some flexible electrical cables, for example, may eventually snap. But the solar panels are doing better than predicted at providing power, in part thanks to the dust devils, which give the robots a spring clean and blow dirt off the panels. And until they do give up, the scientists will stay with them. It's like a year and a half of adrenaline, and we find something new every sol.
The gas-pressurized space suits used by astronauts for space walks and moon landings would never work on Mars. That's the consensus, at least among astrobiologists and simulation experts at the Eighth International Mars Society Convention, which took place 11-14 August in Boulder, Colorado.  A solution, they say, may lie with an old idea. The Mechanical Counter Pressure (MCP) suit aims to use elasticity to provide pressure instead. Paul Webb, a physician from Yellow Springs, Ohio originally proposed this idea in 1968, as a safer and more flexible alternative to the bulky Apollo mission suits. His idea didn't take flight until recently, however, when the US space programme began casting an eye towards the red planet. For future field work on Mars, our number one problem is a space suit that works. Astronauts need something that is light and flexible enough to allow them to scramble about and dig holes, while still protective against the harsh conditions. Webb's suit is made of a stretchy Lycra-like fabric that squeezes the body five times harder than medical support stockings. This makes it difficult to put on, admits Webb. But it is reasonably comfortable so long as the air the astronaut breathes is pressurized to match the suit's constrictiveness. Otherwise, it hurts like hell. The inner suit would have to be covered with an insulating outer shell to regulate body temperature and protect the astronaut against radiation. Unlike an air-filled suit, an MCP suit would still function properly even with a small rip, says Webb; the astronaut's skin would simply bulge slightly to fill the hole. And it weighs only 39 kg, much less than the 180 kg of a standard suit, which in Mars's one-third gravity would be like carting the weight of a person. Webb's suit has been tested in a pressure chamber at an air pressure close to martian levels, about the equivalent of 24,300 metres above Earth's sea level. A test subject managed to pedal a bicycle for an hour in these conditions. A similar MCP suit developed by James Waldie of aerospace company BAE Systems, in Melbourne, Australia, has faced trials by two recent 'crews' at the Mars Desert Research Station (MDRS) near Hanksville, Utah, a test bed for Mars fieldwork. The 'pretend astronauts' roaming the desert in their space suits reportedly found the "really tight long johns" more dexterous and cooler than the standard outfit. But experts at the Mars Society meeting were keen to get even more creative with their imagined space suits for the future. One option, described by Erik Clacey of the International Space University (ISU) in Strasbourg, France, would be to have a suit made of an algae-impregnated fabric that could produce oxygen for the astronaut on-site. The main problem there is in finding a source of nitrogen to feed the bugs. That might be supplied by urea from urine. So you might not want to share suits.
Web resources :
• Mars Exploration Rovers
• Rover science at Cornell University
• Mars Facts
• Mona Lisa Leonardo Project^ref
• Planetary Fourier Spectrometer (PFS)
• Canada France Hawaii Telescope (CFHT)
• NASA Infrared Telescope (IRT)
• Explore Mars with Marsoweb
• Lunar & Planetary Science Conference

Mars news

• Jupiter (5.2 AU from Sun)
• moons :
• Io
• Europa
• Ganymede
• Callisto
• Saturn (9.54 AU from Sun) : the icy particles of Saturn's rings rotate slowly like miniature moons, rather than spinning around wildly as scientists had once thought. Astronomers had assumed that chunks of ice and rock in the rings, ranging in size from dust grains to mountains, were bouncing around like pinballs, frequently slamming into each other. They ought to be spinning out of control. Some rings are packed so tightly that sunlight cannot break through, so collisions should be inevitable. But the Cassini probe, now in orbit around Saturn, has revealed the particles' stately motion by measuring their temperature as they orbit the planet. They find that a particle has a 'hot' side, of about -163 ºC, and a dark side a few degrees cooler. As the particle orbits the planet once every 10 hours or so, the temperature of each face drops by about 15 ºC at the farthest point from the Sun. If the particles were spinning much faster than the time they take to make a complete orbit of the planet, they would experience less of a change in temperature. The rapid rotation would give all parts of the particle an equal exposure to the Sun, like a well-cooked rotisserie chicken. This temperature profile suggests that the particles may make just one rotation for every orbit, just like most of Saturn's proper moons, and indeed our own Moon. This would mean that one face of the particle is always pointing towards the planet. It also means that the particles must warm and cool quite quickly,, something that shards of ice simply don't do. They're more like fluffy, porous snowballs than a solid ice cube. This soft surface might act as a damper on any collisions, explaining why the particles have maintained their gentle motion. Another explanation might be that the particles are charged. This would make them repel each other and reduce the number and strength of collisions. Mission scientists have had a glut of results about Saturn's rings since Cassini started to orbit the poles of the planet. The discovery comes from the first close-up views of Saturn's rings at infrared wavelengths, using the CIRS (Composite Infrared Spectrometer) instrument on board Cassini. Spilker will unveil the results at the American Astronomical Society's planetary sciences meeting in Cambridge, UK, on 4 September.
• moons :
• Mimas
• Dione
• Rhea
• Hyperion
• Iapetus
• Phoebe : it isn't native to its home planet. Instead the lump of rock was captured by Saturn's gravity from rubble left after the formation of the Solar System. Phoebe differs from its fellow moons in having much less ice and much more rock, according to data from the Cassini-Huygens probe's fly-by of the moon on 11 June 2004. This rock-to-ice ratio is similar to objects thought to be remnants of the solar nebula, the cloud of material from which the Solar System formed. Cassini also found that some of the minerals and organic molecules on Phoebe's surface are typical of objects that inhabit the Kuiper belt, a swarm of icy rocks that lies beyond Neptune. The results suggest that Phoebe, which is just over 200 km across, originally came from somewhere in the vast frozen outer reaches of the solar nebula, rather than the hotter, drier inner Solar System where the terrestrial planets formed. Getting to know Phoebe better gives astronomers a glimpse of the solar nebula that spawned the planets we see today. Astronomers already suspected that Phoebe was an interloper, because it orbits Saturn in the opposite direction to most of its fellow moons. Its orbit is also tilted at an unusually large angle to Saturn's equator^{ref1, ref2}. The origin of Phoebe is now pretty much sewn up. Moons usually form as the clouds of gas and dust around planets gel together. Those closer to the planet form in hotter conditions, and tend to be rockier, while lighter molecules such as water are pushed to the outskirts of the dusty disk where they settle as ice on the outermost moons. Depending on how much material is there, this can take as little as 100,000 years. This simple model can be upset if Kuiper-belt objects are flung towards the Sun by Neptune's gravity. Such objects hurtle around a planet like a bull in a china shop, ejecting moons from their proper orbits. There's actually a lot of exchange of material to and from the Kuiper belt. In fact, we see Kuiper-belt objects on the way towards the Sun now; they're called centaurs. > 800 of these objects have been spotted, but astronomers estimate that > 70,000 more of them lie beyond Neptune. Lunine thinks that Phoebe was caught up in this interplanetary exchange, billions of years ago. Once in a while, these things get lucky and get captured by one of the giant planets
• Enceladus has joined the small but select band of moons known to have an atmosphere. The Cassini spacecraft, currently orbiting Saturn, has found a layer of water vapour surrounding the icy moon, which is likely to be issuing from its surface or interior. The probe found that electrically charged molecules around Enceladus are wobbling Saturn's magnetic field as the moon orbits the ringed giant. The frequency of this jitter, measured by Cassini's on-board magnetometer, is characteristic of ionized water molecules spiralling through the planet's magnetic field. At just 500 kilometres across, the moon's gravity is insufficient to keep hold of the water vapour for long. This means that a strong flow of water must continually replenish the atmosphere, suggesting that Enceladus may be volcanically active or possess steamy geysers. 2 other volcanically active moons are already known in the Solar System: Io at Jupiter, and Triton at Neptune. In both cases, gases released during eruptions keep their thin atmospheres topped up. Jupiter's other large moons (Europa, Ganymede and Callisto) have tenuous atmospheres too, but Enceladus is by far the smallest moon to boast a gaseous shroud : it may extend hundreds of kilometres from the surface. Saturn's largest moon, Titan, is the only satellite in the Solar System with a truly thick atmosphere: its surface air pressure is 50% higher than Earth's. Further calculations are needed to determine Enceladus's surface pressure, but it is likely to be similar to that of Jupiter's large satellites. The magnetometer measurements were made during Cassini's last 2 fly-bys of Enceladus, on 17 February and 9 March 2005, when the probe got within 500 km of the moon. The Voyager spacecraft flew past Enceladus in 1981 at a distance of about 90,000 km without detecting an atmosphere. However, since then, scientists have begun to suspect that Enceladus could be the source of Saturn's E ring, made of tiny ice particles. A continuous rain of ice on the moon itself would also keep the surface fresh and clean, possibly explaining why Enceladus is the most reflective body in the Solar System.
• Tethys : pockmarked and ancient, largely made of water ice, and at just > 1,000 km across it is about 5 times smaller than Titan. Countless craters overlap each other, suggesting that the surface has not changed in eons. Cassini will pass within 33,000 km away of Tethys on 24 Sep 2005
• Titan : the only moon in the Solar System with a dense atmosphere, was discovered by Dutch astronomer Christiaan Huygens in 1655. At 5,150 km across it is a monster moon, bigger than the planet Mercury, with a surface temperature of around -180 °C. Ever since Dutch astronomer Gerard Kuiper confirmed in 1944 that Titan had an atmosphere, scientists have longed to explore the smoggy world. Some have speculated that its atmosphere is perhaps like the primeval Earth's, consisting mostly of nitrogen but rich in methane and other hydrocarbons. Titan has a smoggy and constantly changing surface. There are no visible craters and this implies the moon probably has a young surface that is continually refreshed. Astronomers are still unsure whether the flowing patterns on Titan's surface are caused by volcanic eruptions, shifting plates of rock, wind-blown dust or even rivers of liquid hydrocarbons. Cassini-Huygens is the largest interplanetary spacecraft ever flown, and is a joint project between NASA, the ESA and the Italian Space Agency. Dark splotches on Titan's surface, which the researchers suspect may be interconnected lakes of methane, perhaps gusted into waves. Researchers are also puzzling over a series of long, linear streaks of material stretched across the moon's equatorial surface, glimpsed by radar and a near-infrared imaging camera. Like sand ridges shaped by the wind, these might, according to one idea, be particles of material pooled in sheltered areas. A third feature looks something like flows of molten lava from a volcano. But because the moon is thought to harbour a heart of water and ice, the flows may instead be frozen remnants of once-liquid water. Data from Cassini are also strengthening the idea that Titan's surface is swathed in organic, or carbon-based, chemicals, rather than inorganic rock. These might include liquid ethane and propane or solid polymers of acetylene, all preserved at a chilly -179 ºC. Titan captivates space scientists because it is the second largest moon in the Solar System and the only one known to have an atmosphere. Its chemical make-up is thought to be similar to that on Earth long before life emerged. Cassini flew past Titan, roughly 1,200 km from its surface, on Monday 13 Dec 2004, about the same distance as its first close encounter back on 26 October. By comparing images from the 2 fly-bys, scientists have revealed how Titan's atmosphere changes over time. They see for the first time discrete cloud features at mid-latitudes, which means they see direct evidence of weather. Watching the changing weather patterns will allow the scientists to estimate wind speeds and map the overall patterns of atmospheric circulation around Titan.  Cassini also saw that Titan's atmosphere has many more layers of haze than was thought, extending several hundred km above the surface. Our best look at Titan will come when the Huygens probe dives through the atmosphere on 14 Jan 2005. Cassini's remote imaging has not yet revealed what lies on Titan's surface. If Huygens survives its crash landing on the moon, it could finally settle questions about the light and dark patches seen in the infrared measurements that can penetrate thick smog much better than visible light can. It may hit ice, squelch into a tarry soup of hydrocarbons or even splash down into oceans of liquid ethane. However, scientists are positive that Titan's surface is in constant flux, because they have seen no craters from weathering or volcanic activity. Even if it doesn't survive the landing, Huygens will measure every aspect of the atmosphere during its 2-hour hurtle to the moon's surface. It will analyse the chemical composition of the atmosphere, temperatures, wind speed, and even the size of the raindrops in Titan's clouds. Titan is the only moon in the solar system with a dense atmosphere. Some scientists have compared it to Earth's primeval atmosphere, but, with a surface at -180 °C, it is one trapped in a deep freeze. Cassini also flew past the smaller moon Dione on Tuesday 14 Dec, and discovered that wispy surface features previously thought to be streams of ice deposits are actually bright ice cliffs, possibly created by tectonic movement on the moon's surface. The 2.7-m-wide Huygens probe separated from the Cassini mothership at 02:00 GMT on Sat 25 Dec. The European Space Agency's probe has piggy-backed on Cassini for the last 7 years and is destined to dive through Titan's atmosphere, measuring every aspect of its gases and weather. If Huygens survives a bumpy landing, its instruments may also send back details of Titan's surface. The probe will lie dormant until just 4 hours before it arrives at Titan at 09:07 GMT on 14 January 2005, when 3 electronic alarm clocks will rouse it from its slumber. NASA's Cassini craft has already made 2 close passes over Titan that have revealed a little about what Huygens will find there. Huygens will splash down safely into liquid ethane, where it will be able to use its sonar to plumb the depths of the alien sea. However, it could also land in a pool of tarry hydrocarbons or even on icy rock. After its 20-day coast through space, Huygens will be travelling at about 6 km/s when it hits the top of Titan's atmosphere, which extends roughly 1,270 km above the surface. But it will be slowed to a tenth of that speed in just 2 minutes by the drag of the dense atmosphere against the craft's heat shield. Then 3 parachutes will deploy one after the other to float the probe gently down to the surface over 2.5 hours. Cameras will send back pictures during the whole descent, while instruments measure wind speeds and the chemical composition and density of the atmosphere. When it hits the surface, the impact will be roughly the same as if it had been dropped from a standing start about 2 m above the ground on Earth, which will be a nasty knock for the 319-kg craft. The projected landing area is just to the west of Xanadu, a bright area on the surface that has been highlighted by Cassini's infrared camera. If Huygens survives, it will have the chance to relay information collected with its instruments back to Cassini for a further 2 hours before its mother ship disappears over Titan's horizon and it loses contact with Earth forever. This communication window is actually longer than mission managers had originally planned. After Cassini-Huygens launched, engineers discovered that Huygens's transmitter and Cassini's receiver were accidentally tuned to slightly different radio frequencies. NASA changed Cassini's flight trajectory so that transmissions from the receding probe would be Doppler-shifted just enough to bring the frequencies back together. The new trajectory will allow longer contact between the 2. As Huygens heads for Titan, its mother ship will be gathering data on yet another saturnian moon. Cassini will fly past the 2-faced moon Iapetus on 1 January 2005, to study its curious light and dark hemispheres. The Huygens space probe will begin the most important stage of its 7-year journey when it hits Titan's atmosphere at about 9:00 GMT on Friday 14 January. Huygens has lain dormant for the past 20 days as it cruised towards Titan at about 21,000 kilometres per hour. When it flies through Titan's thick clouds the probe will determine the composition of the atmosphere, measure the wind speed and take about 750 pictures, along with a range of other scientific readings. All will be relayed to the Cassini mother ship, and then sent to Earth. But the hydrocarbon smog around Titan has concealed what lies on the surface, so if Huygens survives its trip it may also find seas of liquid ethane, thick tar or icy rock on the -180 °C moon. A trio of alarm clocks will rouse Huygens a few hours before it hits the top of the atmosphere, roughly 1,270 km from the surface. During its first 3 minutes inside the atmosphere, Huygens will use the drag on its heat shield to decelerate to about 1,800 km per hour. The shield will reach almost 2,000°C before a pilot parachute pulls it away and the main parachute slows the probe down to about 320 km per hour. The craft's front shield will fall away at a point 160 km above the surface, allowing the scientific instruments to begin taking readings. A smaller parachute deploys at 120 km from the surface, replacing the large one and giving Huygens a total of around 2.5 hours of flight through Titan's skies. Scientists hope that the clouds will clear below 70 km' altitude, giving Huygens' 3 cameras a clear view down to the surface. When the probe is just 20 km away from impact it will send all its data back to Cassini. Once Huygens falls silent, Cassini will turn its radio transmitter toward Earth to return the precious information, a trip that should take 67 minutes at light speed. By the time Huygens is 5 km above Titan's surface, it should be able to tell from which chemicals the surface is made. With 700 m to go, a searchlight will switch on to pick out small features at the landing site. If Huygens survives its crash landing, and its batteries hold out, another suite of instruments will study the chemistry of the moon itself, sending back data to Cassini until the mother ship disappears over Titan's horizon. ESA is responsible for the Huygens craft, and scientists have already gathered at the mission control centre in Darmstadt, Germany, where they expect to get the first data from Titan by about 15:30 GMT on Friday. Scientists have been celebrating throughout the weekend after the Huygens probe successfully landed on Titan, Saturn's largest moon, on 14 January. After some 20 years of planning and a 7-year journey through the Solar System, the probe penetrated Titan's thick atmosphere, and landed safely on solid ground 2 hours later, at 12:34 GMT. During its parachute flight, Huygens carried out several experiments to investigate Titan's atmosphere and surface. Photos have provided the first glimpse of the moon's surface, which is normally obscured by the atmosphere. At the beginning of the day, scientists and officials involved in the mission looked tense as they waited in the control room of the European Space Operations Centre in Darmstadt, Germany, for signs of life from the probe. Then at 10:40 GMT the news arrived. The Robert C. Byrd Green Bank Telescope of the US National Radio Astronomy Observatory in West Virginia had retrieved a carrier signal from Huygens at 10:25. This meant that the most critical phase of diving into the atmosphere had been accomplished. In a brutal braking manoeuvre, Huygens had been slowed by Titan's atmosphere from > 20,000 km/hr to a tenth of that, a process that heated the front shield to 1,600 °C. The front and back shields had then detached, and the probe was transmitting a continuous signal. The carrier signal identifies Huygens, but contains no data from the probe's instruments. So many questions remained. Would the scientific experiments be properly carried out during the 2-hour parachute descent? And what would happen to Huygens after the impact on Titan? The nervousness increased when the moment for receiving data arrived. At 16:16 GMT, the signals bearing the scientific information should have finished their 1.2-billion-km journey from Cassini to Earth. The eyes of the scientists and ESA officials were glued to the computer screens in the control room. 2 dozen television cameras and hundreds of journalists in the overcrowded press centre watched them, trying to judge from their reactions what might be happening. The moment came and went. Then, at 16:19, the tension was broken. Scientists started jumping up and down, and Claudio Solazzo, Huygens' operations manager, fell into the arms of his colleagues. Some minutes later, they arrived at the press centre to explain that Huygens' scientific instruments were working properly, and all the expected information was being retrieved. This means that all 6 experiments are getting good science. In a view from about 16 kilometres up, drainage channels can been seen, which scientists say might have been shaped by liquid methane or ethane. Another picture taken on the ground doesn't look particularly alien at all. It shows a distinctly Earth-like location, with flat ground strewn with icy blocks of about 20 centimetres across. This image was taken from an altitude of 8 km. It shows what could be the landing site, with shorelines and boundaries between raised ground and flooded plains. Scientists hope to learn about the early evolution of Earth from the experiments on Titan. The moon, which is the only one with an atmosphere in our Solar System, is about 10 times farther from the Sun than Earth is, and the amount of energy that reaches it is about a hundred times less. That means that physical and chemical processes have been happening much more slowly on Titan than on Earth, and scientists believe it may resemble a cold version of the Earth billions of years ago, before life began. The pictures show an orange world littered with small rocks made of water and hydrocarbon ice, frozen at -180 °C. During the descent Huygens also saw what seemed to be drainage channels snaking towards a dark shoreline, confirming scientists' suspicions that Titan could have seas of liquid methane and ethane. White streaks in the aerial images are likely to be ground fog made of methane. Erosion around the base of the rocks, which range from 5 to 20 cm across, may indicate that a liquid has flowed around them, just like the depressions around rocks on a damp beach. The first images came from a point about 16 km above the surface. Titan is about 1.2 billion km away from Earth, and is the first moon other than our own to be explored. It is the only moon in the Solar System with a significant atmosphere, and is thought to have a composition similar to Earth's primitive atmosphere. When it crashed into Titan, Huygens' rod-like 'penetrometer' encountered a relatively hard crust before sinking about 15 cm into the ground. This suggests that the surface has the consistency of wet sand or crème brûlée. Scientists had been concerned that the scientific instruments of Huygens might not survive the impact on Titan. But after a 2.5-hour descent, a soft landing allowed Huygens to continue sending signals for at least another 70 minutes after it reached Titan's surface, at 12:34 GMT. The moon's soil seems to be a sticky tar of hydrocarbons. Huygens' mass spectrometer detected methane, ethane, acetylene and other hydrocarbons evaporating from the probe's landing site. Huygens relayed its data to the Cassini craft passing overhead, which collected all the transmissions before turning towards Earth to beam them to NASA's Deep Space Network, a trio of powerful radio antennas based in California, Spain and Australia. In fact, a joint effort between 18 radio telescopes around the world also managed to pick up most of Huygens' faint signals directly, even though they are only as strong as a mobile-phone transmission. Although the mission has run almost flawlessly, there has been one set-back. Huygens was meant to send back its data along 2 different radio channels, but one of them failed. While most experiments were recorded on both channels, about half of the 700 expected images were lost, along with information about the winds in Titan's atmosphere. The ESA is planning a full investigation to find out why some of the probe's data were lost. The radio telescope interceptions have rescued the wind measurements, allowing scientists to reconstruct what Huygens heard as it plummeted towards the ground. Scientists have already estimated that winds were travelling about 25 kilometres per hour in Titan's atmosphere. The probe's radar measured the distance to Titan's surface as it fell - the rising sound can be turned into detailed information about the craft's trajectory. The Cassini craft will continue sending back postcards from its tour of Saturn and its moons until at least the middle of 2008. More images from Titan have confirmed scientists' expectations that a complicated cycle of weather is shaping the surface of Saturn's largest moon. It looks as if there are rivers, cliffs, lakes and clouds. The pictures show terrain that is covered with sinuous drainage channels winding around a range of hills towards a dark area that looks like an ocean. The interpretation of these pictures should be obvious to anyone who has seen an aerial view of Earth. We see the same features every time we fly over a coastline. There's no evidence yet of liquid in these rivers, they look more like Arizona's dried-up river beds. But those canyons didn't carve themselves. The surface rubble snapped by Huygens also bears the marks of flowing liquid hydrocarbons such as methane and ethane: they're very smooth, there's definitely some fluvial process that shaped them. Scientists had speculated that Titan could be a cold analogue for conditions on the primordial Earth, and these early discoveries bear that out. There's no evidence for life, but we do see all 3 phases of matter, and transport mechanisms between them: evaporation, clouds, rain and rivers. This provides the opportunity for the development of complex organic molecules. Titan's surface also seems to be remarkably fresh. Counting the number of craters on a moon and comparing it with the number of meteoroids in the area gives astronomers a way to calculate the age of a moon's surface. The younger the crust, the fewer craters are visible. One thing's for sure: Titan's not cratered. Unlike the other moons in the Solar System, Titan has a thick atmosphere, so smaller meteors may burn up before they hit the ground. This makes it more difficult to estimate the age of the surface, but it's probably less than 10 million years old. In some areas, the surface is very bright. This suggests that liquids wash dark tars from the icy surface quite regularly. This might be a sign of methane rain. Smith is now piecing together images taken in the last kilometre above the landing site, which was illuminated by a lamp on the bottom of the probe. Huygens' had quite a big bang, hitting the surface at about 3.5 metres per second, equivalent to 12.6 kilometres per hour. The probe has made a dent in Titan's surface that is a few centimetres deep. The soil seems to be made up of grains of water ice glued together by sticky hydrocarbons such as methane, giving it the consistency of putty. Huygens hit the ground just 8° from vertical, suggesting that winds were not strong enough to blow it around much. The mosaic image released today confirms this. Because Huygens' on-board camera was looking down at a slight angle, it took pictures of the ground beneath looking in all directions as the falling probe spun round. But it was not able to see directly downwards. If the probe had been drifting during its descent this wouldn't have mattered, but the dark patch in the centre of the mosaic means that the probe must have remained over the same area of ground as it fell. The parachute didn't fall on top of the probe. A group of enthusiastic amateurs managed to process raw images of Titan from the Huygens probe faster that any of the giant space agencies in charge of the mission. NASA and the ESA usually process images from space missions using sophisticated computer software before being releasing them to the public. Changing the contrast, brightness and even colouring the pictures can help to pick out key features that would otherwise go unnoticed. But with the Huygens mission (and NASA's Mars Exploration Rover Mission in 2004), the scientists involved released the raw images as soon as they came in. Once Huygens' mother ship, Cassini, had beamed information from the probe back to radio receivers on Earth on Friday 14 January, the raw images were posted on the descent-imaging team's website, based at the University of Arizona, Tucson. Computer enthusiasts pounced on the images immediately, and improved them using a range of free or commercially available software before swapping their pictures in Internet chatrooms. When Liekens tuned into the ESA press conference on the morning of Saturday 15 January, he was disappointed by the quality of their images. So he decided to host amateur compositions on his website. The site has quickly turned into a virtual gallery. Many amateurs have also taken images from the 2 Mars rovers Spirit and Opportunity, and turned them into detailed topographic maps and panoramic landscapes. But this is the first time enthusiasts have beaten the space agencies to the punch. Not all of the pictures will be scientifically reliable, something that ESA and NASA obviously have to take care over. One stunning landscape was produced by Mike Zawistowski, a freelance computer-repair expert based in Boston, Massachusetts, using Terragen, a freeware program that converts the basic brightness data in aerial pictures into a topographical map, to generate the ground-level vista shown at the top of this page. He used information from one of Huygens' aerial photos, and worked out the correct scale based on its resolution - about 20 to 40 metres per pixel. The final image was adjusted for colour. One aspect of the mission that hasn't been trumpeted quite so loudly is the fact that not all of Huygens' data actually arrived on Earth. So what happened to the rest of them? Scientists on Huygens' imaging team only got half of the pictures they had hoped for during the descent. They expected to have > 700 images from the 2.5-hour flight, and only got about 350. Data from the Doppler-shift experiment, which measured subtle changes in the wind speeds that Huygens experienced, was also lost. As it fell towards Titan, Huygens transmitted a continuous stream of information to the Cassini mother ship passing overhead, which collected all the data before turning towards Earth to send it to the waiting scientists. The Huygens transmissions were sent on 2 channels that used slightly different microwave frequencies. Most of the probe's data were duplicated on each channel, like 2 different radio stations broadcasting the same programme. That redundancy saved the mission from failure. Cassini had 2 different receivers to collect the data from Huygens, and one of them did not work. Why didn't the receiver work? The Channel A receiver was simply not turned on during the mission. Any instructions that need to be sent to the Cassini spacecraft are compiled as a series of software commands by mission scientists, and these are transmitted to the craft from the Jet Propulsion Laboratory in Pasadena, California. All commands relating to the Huygens probe were programmed by ESA. The error should have been picked up during checks. ESA is now mounting an investigation into why the mistake was not spotted. Why were the pictures not duplicated like the rest of the data? The imaging team, based at the University of Arizona, Tucson, sacrificed the redundancy of the system in an attempt to get as much data as possible from Titan. Instead of sending the same pictures twice they interleaved them across both channels, with successive images being sent to alternating receivers on Cassini. If it had worked, they would have got 700 images. And because the pictures were alternated between the 2 channels, the scientists still have a continuous pictorial record of the descent. The Doppler Wind Experiment was designed to calculate the direction and strength of Titan's winds, to find out more about the moon's weather and to precisely plot Huygens' trajectory and landing point. As the probe fell away from Cassini, its microwave transmissions were 'stretched' slightly - Cassini would have picked up a lower frequency than Huygens actually sent. This tiny Doppler effect can be related directly to the probe's motion. But the effect is so small that it can only be discerned if both transmitter and receiver operate at an extremely regular frequency. To achieve this stability, one of the two data transmitters was fitted with an ultra-stable oscillator (USO). Weight constraints prevented both transmitters from being fitted with a USO. But this made the experiment dependent on a single channel - the channel that Cassini failed to pick up. Fortunately, a network of radio telescopes on Earth picked up the signal from the ultra-stable transmitter directly. This should allow scientists to reconstruct the craft's flight path within the next two weeks, although it will require a huge amount of number crunching. Saturn's giant moon has rain and rivers very similar to those on Earth, the planetary probe Huygens has discovered. But on Titan they consist of liquid methane rather than water. Photographs of the distant world revealed that Titan's rain has shaped a system of river beds and basins, by draining from the ridges to the plains. The rivers and lakes appear to be dry at the moment, but methane rain may have fallen within the past few weeks. As the probe landed, its penetrometer pushed 15 centimetres into the ground, which has the consistency of loose sand. Its impact generated enough heat to release methane gas, which was detected by the craft's mass spectrometer. The presence of methane at the surface hints that liquid methane rain must have fallen recently. On Earth, methane is generated mainly by biological agents such as bacteria. But on lifeless Titan, it probably bubbles up from the moon's insides.  This theory is supported by the analysis of atmospheric gases during Huygens' descent. Whereas the concentration of nitrogen (the main component of Titan's atmosphere) was stable, the methane concentration increased during the final 3 minutes of the craft's journey. Mission scientists also suspect that the white haze seen in the first picture is mainly methane. The composition of Titan's solid ground has thrown up a shock: it's made of water ice rather than rock. Photographs of the landscape that show the same region from 2 different angles have highlighted a clear distinction between the bright hilltops and darker valleys. Hydrocarbon particles may have been washed from the ice by methane rains, pooling in recesses such as river basins to give the darkened effect. The mission has also found signs of volcanic activity on Titan. An analysis of the element isotopes found at the surface suggests that the volcanoes spewed out water and ammonia, rather than molten lava. NASA has mostly explored places thought to contain liquid water, either now or in the past. It has sent craft to Mars, where ancient rivers seem to have carved the surface. And it has staged fly-bys of Jupiter's icy moon Europa, thought to have a watery ocean below its frozen surface. Earth demonstrates the logic in this. Life is found just about everywhere there is water and a source of energy, and water seems a prerequisite for every form of life. This makes some scientists pessimistic about life on Titan. But does life depend on water? Or could it be that Earth life has evolved to suit its watery home? Anything we might recognize as life probably needs a liquid solvent to transport molecules and bring them together. But who says the solvent must be water? Water-free environments on other worlds might fulfil the conditions for life^ref. Liquid ammonia is rather similar to water: it dissolves molecules with electrically charged parts, including carbon-based (organic) ones. On Earth, ammonia boils at -33°C; but there are many places in the Solar System where it could exist in liquid state, such as the clouds of Jupiter. Other worlds could support exotic solvents: all of the gas giants might contain patches of dense, liquid-like hydrogen in their atmospheres, and Venus has clouds composed of droplets of sulphuric acid. But Titan looks like the best candidate for non-aqueous life. It seems to have rivers and oceans, and its sticky surface is apparently made partly from organic molecules. There are nitrogen-containing organic compounds called nitriles in its atmosphere, which, it has been suggested, could react with water ice to form a rich blend of organic ingredients for possible life forms^ref. Non-aqueous solvents such as hydrocarbons can support complex organic reactions. In fact, organic chemists usually prefer them to water, which is reactive and can interfere with delicate chemical processes. One of the puzzles about the origin of life on Earth is why the first biological molecules were not torn apart by reactions with water. Life evolving in hydrocarbon liquids would not have this problem. Because of water reactivity, the human genome survives only because it is constantly being repaired. Even on Earth, many of the chemical reactions of life take place without water, catalysed by enzymes with water-repellent pockets. And many enzymes work perfectly well in the oily, water-free environment inside cell walls. Relatively weak hydrogen bonds give terrestrial biomolecules, such as the DNA double helix, the crucial ability to stick together and then separate. But water molecules form hydrogen bonds too, so groups of molecules bound by hydrogen bonds can fall apart rather easily in water. In ethane a hypothetical form of life would be able to use hydrogen bonding more. So it's not obvious that water is special, apart from the fact that it exists in large quantities on Earth. If life is an intrinsic property of chemical reactivity, life should exist on Titan

A fly-by of the saturnian moon has revealed varied terrain, including 2 impact craters and some mysterious parallel lines. And data sent back from the European Space Agency's Huygens probe hint that a complex mix of organic molecules could be present in its ice. A previous fly-by on 26 October 2004 revealed features that seem to have been caused by volcanic flows, which were probably a frosty mixture of ammonia and water and had the consistency of basalt lava. Similar features showed up in the latest pass. In a close fly-by of Titan on 15 Feb 2005, the Cassini spacecraft, on which Huygens hitched a lift, scanned a strip of ground around the moon's equator, equivalent to about 1% of its surface : the most impressive feature is a huge impact crater, around 440 km across, named Circus Maximus. The crater has been considerably eroded over time, with roughened edges, and various hills and channels scarring its centre. Further east lies a smaller crater, just 60 km across. The crater was created when a comet or asteroid roughly 5 to 10 km wide slammed into Titan. Titan has much fewer craters than expected for its age. Volcanic flows and tectonic activity are continually reshaping the terrain. The surface is < 25% of the age of the Solar System. Elsewhere lie dark plains and channels, like the ones the Huygens probe saw on its descent to the moon's surface on 14 January. And there are some intriguing dark lines. Perfectly parallel, they have been dubbed "cat scratches", but scientists are mystified about how they formed. They could be sand dunes shaped by the wind. In a busy week for the spacecraft, Cassini made its first close fly-by of Saturn's moon Enceladus on 16 February. It snapped pictures of the icy moon's surface, which is the most reflective surface in the Solar System. The craft flew just 1,180 km away from the moon, and images reveal terrain fractured by cracks and covered in ridges. The lack of craters suggests that, like Titan, the surface of Enceladus is constantly being refreshed by a lava-like mixture of frozen chemicals. Although Huygens has confirmed the presence of large amounts of methane on Titan, they have found very little of the ethane they had expected. When methane molecules are broken down by UV radiation that has penetrated the atmosphere, 2 of the fragments generated can potentially combine to form ethane. But the relative lack of ethane suggests that the fragments may be reacting further, for example, by combining with the nitrogen in the atmosphere. The photochemistry goes further than the models suggested, to more complex things : the chemistry may resemble that of the early Earth, before life began. Huygens detected organic molecules at its landing site, but it is not yet clear how complex they are. We might find some of the precursor molecules of life frozen in the ice. Although pictures of Titan seem to show rivers, deltas and oceans, Saturn's giant moon is as dry as a bone : the moon has methane in its atmosphere, and this could come from fumes evaporating from giant lakes of hydrocarbons. They envisaged rainstorms of liquid methane and other wild weather events on the alien surface. So they eagerly anticipated pictures from the Cassini probe, a joint venture between NASA and the European Space Agency, which flew past Titan on 26 October 2004 and peered through the moon's thick smog using its Visual and Infrared Mapping Spectrometer. Surprisingly, a detailed analysis of these images has shown no significant bodies of liquid anywhere on the moon^ref. Instead there are signs of a volcano. And this could be a source for the 'river channels' that Cassini's piggybacking partner, Huygens, saw when it landed on the moon. The data do not absolutely rule out the possibility of liquid on the surface. But they do certainly exclude the possibility of giant lakes or oceans. The survey team found a 30-km-wide dome, which could be a volcano. It has a depression at the top that looks like a caldera, the collapsed top of a volcanic vent. And flow lines radiate from the dome, as if particles of ice have been scattered by an eruption. This might explain the river channels : Titan's surface is a crust of dirty ice, tens of kilometres thick, which is slowly circulating and drawing up material from deep inside the moon. Rising chunks of ice could bring trapped methane with them, which would be released as a gas when it reached the surface. The methane could then gather into hydrocarbon storm clouds that pour rain on to the surface, causing flash floods that carve the deep channels. Maybe we're just in a dryish period at the moment. The key question to answer is whether the channels were carved by an annual flood, or by a freak event millions of years ago. The absence of significant craters on Titan suggests that the surface has been swept clean relatively recently, and observations during Cassini's remaining 3 years around Saturn should provide interesting data. This false-colour mosaic of Titan was constructed using six medium-resolution (25 km per pixel) infrared images obtained during the Cassini flyby of 26 October 2004. The colours correspond to atmospheric (red) and surface (green and blue) features that are not visible to the human eye. The inset shows a high-resolution (2 km per pixel) image taken using a 2.30-µm filter near the point of Cassini's closest approach to Titan (1,200 km).

An intelligent floating robot could help to explore Titan, following flight tests that prove it can survey large areas of land completely autonomously. The aerobot is even smart enough to avoid dangerous turbulence. After the Huygens probe returned those stunning pictures of Titan's surface, there's been a lot of interest in another mission. The aerobot could spend months cruising through the moon's atmosphere, mapping the surface and collecting samples. Aerial vehicles fill the gap between orbiters and ground-based robots. Orbiting satellites can map large areas of moons or planets, but resolving small features on the surface is extremely difficult, especially if they are obscured beneath a cloudy atmosphere such as Titan's. And although rovers such as Spirit and Opportunity can see a lot more detail, they have a very limited range and rely on constant supervision from mission managers back home. The team tested the artificial intelligence of its 11-m-long airship over a dry lake bed in El Mirage, California, in 2004. The craft was able to explore areas that lay several km away from its launch site in less than an hour, working out its own route between sites of interest that had been chosen by scientists before the flight. The robot corrected its path whenever it was blown off course, and could also assess danger from air turbulence by sensing wind speeds, changing its altitude to reach calmer air when necessary. The aerobot currently relies on the Global Positioning System, or GPS, to plot its course, but a Titan explorer would not have that luxury. So the team has trained the robot to track its own position using the photographs it takes of the ground. Elfes started work on the autonomous airship in the late 1990s, while he was director of the Automation Institute in Campinas, Brazil. He hoped that the craft would be used to monitor the health of the country's rainforests. But although it could find its own way from place to place, that version of the aerobot still needed a human operator to get it out of trouble. As radio signals take about 90 minutes to travel from Earth to Titan, and can be blocked for days at a time by Saturn, developing better artificial intelligence was essential for any future mission. "You really need a system smart enough to detect danger and react to it. While his team works on the aerobot's brains, a sister project at the Jet Propulsion Lab is developing a tough helium balloon that could be flown to Titan and inflated on arrival. The craft would avoid landing, but could skim low enough to drop probes or sampling devices on the ground. This summer, aerobot's team got further funding to develop a full mission proposal, which may lead to a launch in 2012. The aerobot could do active duty on other planets with substantial atmospheres, such as Venus. But similar craft might be used on Earth much sooner. Deployed at high altitude, they would provide a cheaper alternative to telecommunication satellites, and could be particularly useful for quickly re-establishing lines of communication over disaster areas.
Web resources : US$3.3-billion Cassini-Huygens mission is the largest interplanetary spacecraft ever flown, and is a joint project between NASA, the European Space Agency (ESA) (responsible for the Huygens probe) and the Italian Space Agency
• Uranus (19.2 AU from Sun)
• moons :
• Puck
• Miranda
• Ariel
• Umbriel
• Titania
• Oberon
• Neptune (30.1 AU from Sun)
• moons :
• Triton
• Nereid
• Pluto (39.4 AU from Sun; diameter : 1,400 miles)
• moons :
• Charon
• asteroid Ida :
• moons :
• Dactyl
• Quaoar (diameter : 800-1,100 miles), a mysterious object in the outer reaches of the Solar System, contains ice crystals, suggesting that Quaoar and many similar objects could be much warmer and more geologically active than had been thought. Apart from Pluto, Quaoar is the largest known object in the Kuiper belt. This region lies beyond Neptune's orbit and is filled with icy rubble that formed during our Solar System's birth > 4.5 billion years ago. Because Kuiper-belt objects lie > 4.5 billion km from the Sun, astronomers had thought that they were unlikely ever to get warmer than about -223°C, which is just 50°C above absolute 0, the coldest temperature possible. At that temperature, the ice on Quaoar should be amorphous, but it is not at infrared observations of the rock, which show that the ice has a repeating crystalline pattern, similar to that seen in snowflakes. The crystalline pattern means that when the ice formed, Quaoar must have been warmer than -163°C. Below that temperature, water molecules stick together in random patterns to form amorphous ice. But if it is warmer than that, the molecules can jiggle around enough to fall into a regular pattern that makes for a more stable arrangement. Quaoar has a nearly circular orbit that never brings it near Neptune, so the orbit has probably been stable since the Solar System formed, ruling out the idea that Quaoar was heated by moving closer to the Sun. Another possibility is that the surface could have been warmed by the impact of tiny meteorites, but this is unlikely because ammonia is found trapped in Quaoar's ice. Because this chemical is more volatile than water, surface bombardment that heated the ice would eventually remove any ammonia that was present. So the crystalline water-ammonia mixture is more likely to have been formed inside Quaoar, warmed by the radioactive decay of elements such as uranium and thorium. Such heating could also trigger 'cryogenic volcanism'. Such volcanism involves explosions of gas and liquid that bring underground reservoirs of the ice crystals to the cold surface. But it would not be active today despite it is a progressing process. Crystalline surface ice would be unlikely to survive bombardment by the solar wind and cosmic rays for > about 10 million years. The first Kuiper-belt object was spotted in August 1992, and dozens mor have been found since. Calculations predict that there are > 70,000 objects in the belt with diameters > 100 km, providing a pool of icy objects that may supply the Solar System with short-period comets. So far, the researchers have only identified water and ammonia on Quaoar, but the object probably also contains silicate rocks and some carbon-containing materials^ref




The conditions in giant planets are extreme: heat > 1,000 ºC and pressure some 100,000 times what we are used to. Ordinary substances could behave in very strange ways inside these scalding behemoths. It has been predicted for some years that water under such conditions would act neither as a straightforward solid or liquid but exist in a 'superionic' phase, in which the oxygen atoms are essentially frozen, but the hydrogen atoms can whiz around at high speed^ref. Laurence Fried and his colleagues at Lawrence Livermore National Laboratory (LLNL) in California decided to see if they could get water to go superionic. To create the immense pressures they needed, the team used a device that smashed water between 2 diamonds. They then heated the water with an infrared laser beam. As they did so, the researchers monitored the frequency with which the water molecules vibrated, and looked out for an abrupt shifts in frequency that would signal that the water had altered its state, or 'phase'. The researchers also studied computer models of the atoms' behaviour, which suggested that the water had indeed entered a superionic phase, a strange state between solid and liquid. Tracking a group of some 60 simulated atoms took weeks, and required computing power equivalent to 1,000 laptops. The model showed that as temperature and pressure increase, the molecules break apart, settling into a non-molecular pattern that is denser than normal ice. Beyond that, it shifts to the superionic. If you brought such water into a regular room on Earth, it would explode, but inside a planet it would be hard as iron and so hot that it would glow bright yellow. If superionic water really does exist in the hearts of giant gas planets, there might be more of it in the Solar System than there is of more familiar types of water. What's more, its potentially excellent electrical conductivity might account for the huge magnetic fields of planets such as Neptune and Uranus^ref.

• extrasolar planets / exoplanets : > 130 extrasolar planets have been detected by watching how their orbit makes their parent star wobble. But none has been imaged directly, because a planet's dim glow is mostly swamped by the light of its star. This wobble is caused by the gravitational tug of the planet on the star. Because stars are much bigger than planets, the effect is tiny, and it is only in the past decade that telescopes have been sensitive enough to detect it. Even then, the wobble is detectable only for giant planets, which are those about as big as Jupiter, the bloated ball of gas in our Solar System. It is not possible at present to detect planets as small as the Earth. Jupiter is not habitable: it is too cold, and is mostly composed of dense gas. And it is unlikely that extrasolar giant planets would support life either. But astronomers generally assume that if they detect such a planet in a distant solar system, it is likely to be accompanied by other, smaller planets. And maybe some of the smaller planets in these systems are just like Earth. But the properties of almost all the known extrasolar planets are quite different from those of Jupiter. There are 110 of these extrasolar planets, at the latest count, and they are all between about a tenth and ten times as massive as Jupiter. Most of them are, however, much closer to their sun than Jupiter is to ours: they are known as 'hot Jupiters'. They also tend to have more elongated orbits than those of Jupiter and the Earth, both of which orbit the Sun on almost circular paths. Other planets were not formed by the same kind of process that produced our Solar System, so they might not have smaller, habitable companions. The planets in our Solar System were put together from small pieces. The cloud of gas and dust that surrounded our newly formed Sun agglomerated into little pebbles, which then collided and stuck together to form rocky boulders and eventually mini-planets, called planetesimals. The coalescence of planetesimals created rocky planets such as Earth and Mars, and the solid cores of giant planets such as Jupiter, which then attracted thick atmospheres of gas. But that is not the only way to make a solar system. Giant planets can condense directly out of the gaseous material around stars, collapsing under their own gravity. This process, which generates giant planets with a wide range of orbital radii and eccentricities, does not seem capable of producing the rocky planets seen in our own Solar System, which is why it has generally been ignored^ref. Although astronomers have identified more than 120 worlds orbiting other stars, none has been pictured directly and researchers are still looking for evidence to confirm that these fuzzy blobs are indeed planets. Direct observation of a planet would allow astronomers to work out the composition of its atmosphere, and perhaps even its surface. A group of astronomers working in Chile may have taken the first picture of a planet outside our Solar System orbiting a small, faint star called 2M1207 about 230 light years away^ref. The hunt for direct images of planets outside our Solar System has bagged its strongest candidate yet. Recent observations from the Hubble Space Telescope have confirmed a previous sighting made in April 2004. Astronomers say they are now 99% certain that the dim and distant blob is indeed a planet. Astronomers would love to have direct snapshots of planets because their light carries information about their chemical composition. To improve their chances, researchers look for planets using infrared light rather than visible light, because this makes planets much brighter relative to their parent star. A team of scientists from the European Southern Observatory (ESO) have been using the Yepun telescope on top of Paranal Mountain in Chile. They were the first to spot the possible planet, which is orbiting a small, faint star about 230 light years away, called 2M1207. It was still possible that the object wasn't orbiting the star at all, and was simply on its way past. But Hubble observations, made on 28 August 2004, found that the object's position had not changed over the preceding 4 months, making it much more likely that the object is an orbiting planet. The scientist who led the latest Hubble observations is keen to remove his last 1% of uncertainty. More data are needed to confirm the find : Hubble observations planned for April 2005 will give a definitive answer one way or the other. The candidate planet and its parent brown dwarf are thought to be about 6.5 million years old, and are roughly 8 billion kilometres apart, farther than the distance between the Sun and Pluto. Weighing in at 5 times the mass of Jupiter, the candidate glimmers at a temperature of around 1,500 °C. Preliminary analysis of its infrared light suggests that water and carbon monoxide are present in the atmosphere. The result comes < 2 weeks after a rival team of planet hunters admitted that their possible exoplanet discovery, announced in May 2004, was not a planet after all. Steinn Sigurdsson and John Debes of Pennsylvania State University, University Park, had used the Hubble Space Telescope to spot an object around a white dwarf about 100 light years away. But follow-up observations with the Gemini North Telescope in Mauna Kea, Hawaii, showed that they had in fact seen an unrelated background object rather than a genuine planet^ref. Astronomy is at times a science of unexpected discovery. When it is, and if we are lucky, new intellectual territories emerge to challenge our views of the cosmos. The recent indirect detections using high-precision Doppler spectroscopy of > 100 giant planets orbiting > 100 nearby stars is an example of such rare serendipity. What has been learned has shaken out preconceptions, for none of the planetary systems discovered so far is like our own. The key to unlocking a planet's chemical, structural, and evolutionary secrets, however, is the direct detection of the planet's light. Because there have been as yet no confirmed detections, a theoretical analysis of such a planet's atmosphere is necessary for guiding our search^ref. Light from planets outside our Solar System has been genuinely detected for the first time. The breakthrough marks the end of a long race between astronomers to image an alien world directly, without recourse to theoretical detective work. Although > 130 extrasolar planets, or exoplanets, have been discovered, almost all were found by detecting the way they make their parent stars wobble as they orbit. Visual identification is difficult because light from the star swamps the relatively dim glow of a planet. So astronomers have been looking for infrared light from these planets, because their emissions in this area of the spectrum tend to be much brighter than any visible shine they have. The infrared light can reveal details of the planet's temperature and chemistry, but conclusive evidence has proved elusive. Now two research groups say they have definitely spotted infrared light from two different exoplanets using NASA's orbiting Spitzer Space Telescope. In both cases, the planet's orbit seems to take it across the face of its star before disappearing behind it. With each transit and eclipse, the total amount of infrared light coming from the region rises and falls. By subtracting the constant starlight, the astronomers are left with a measure of the light from the planet itself. It's an extremely important milestone : these are the first steps along the path to identifying Earth-like planets. The 2 planets are already known, despite the fact that no one has seen them before. One of them, HD 209458b, was the first exoplanet ever found to transit its star, although astronomers didn't realize this when they first discovered it^ref. The second group, led by David Charbonneau of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, has made similar measurements of a planet called TrES-1^ref. Both planets are classed as 'hot Jupiters'. These are massive objects that take about three days to complete an orbit a few million miles from their parent stars, far closer than Jupiter is to our own Sun. "It's one of the most significant detections ever made. HD 209458b is between 850°C and 1450°C, and is likely to have water vapour in its atmosphere. Further observations and computer modelling should pin down its precise temperature, and reveal more about its atmospheric chemistry. It's an awesome experience to realize we are seeing the glow of distant worlds : TrES-1 is about 800 °C. Astronomers will now rush to test the technique on other star systems : they will be limited to similar hot Jupiters that transit their stars, but it's a step in the right direction. HD 209458b and TrES-1 are 2 of just 6 known transiting hot Jupiters. Cooler planets that lie further away from their stars take much longer to complete an orbit. Several circuits are needed to check and recheck light readings and with limited space telescope time available, Earth-like worlds that take months to complete an orbit will require long-term observations by telescopes dedicated to the task. But both NASA and the European Space Agency are planning space telescopes that will hunt specifically for Earth-like worlds. Planets orbiting other suns could be made partly of pure diamond : some 'extrasolar' planets may have condensed from gas and dust that is rich in carbon. This could produce worlds made largely of hard carbon compounds such as silicon carbide, otherwise known as the industrial abrasive carborundum. These planets might have thick crusts of almost pure carbon. Their uppermost crust would consist of graphite, but deeper down, high pressure would transform graphite into the other more glamorous form of carbon: diamond. What's more, carbon on the surfaces of these planets could form hydrocarbons, giving them soft, tarry coatings, or even lakes and seas of liquid hydrocarbons such as methane. The recent images of the surface of Saturn's moon Titan, taken by the European Space Agency's Huygens spacecraft, suggest that this world may have such 'petroleum' rivers and lakes, although the moon's solid fabric is thought to be ice, rock and iron.  Jupiter's methane-rich atmosphere is evidence that this giant planet condensed around an initial nucleus of carbon-based material. It is generally thought that the planets in our Solar System have cores of metal (iron and nickel) and rock (silicates, like the rocks on Earth). These would be the first materials to condense out as the gas and dust cloud, or nebula, that surrounded the Sun when it first formed, began to cool down. But carbon-rich material could have accumulated in a ring called the 'tar line' around the Sun, where carbon gases diffused outwards and then condensed. Carbon-rich dust grains from the outer nebula would also spiral inwards and add to this tar line. There was plenty of carbonaceous material in the early solar nebula, and some of it still roams the Solar System as rocky lumps called carbonaceous chondrites, which occasionally fall to Earth as meteorites. In contrast to gas-giant planets with carbon-rich cores surrounded by huge amounts of gas, some carbon planets might be more like Earth: solid, smaller than Jupiter, and perhaps with a thin layer of atmospheric gases such as methane or carbon monoxide^ref. 'Rain' from these atmospheres would create oceans of tar on the planetary surface. The centres of these planets would probably consist of silicon carbide or titanium carbide. But the researchers argue that a thick layer of graphite could form on top of this. And at depths of a few kilometres, this would be transformed into diamond. As carbon is the key element in terrestrial life, it is possible that life - perhaps even intelligent life - might exist on an Earth-sized carbon planet. Whatever such beings might be like, in their oil-rich world they would not go to war over such a common trifle as carbonaceous fuels.

The hunt for worlds outside our Solar System has found its smallest planet yet: it weighs in at just seven-and-a-half times the size of the Earth. Astronomers have already found more than 150 extrasolar planets, also known as exoplanets. But all of them are larger than Uranus, which has 15 times Earth's mass. The recent find is so small that it is likely to be rocky, its discoverers say, rather than a gas giant. This is the smallest extrasolar planet yet detected. It's like Earth's bigger cousin. The planet orbits the star Gliese 876, which is just 15 light years from our own Solar System and is already known to have two Jupiter-sized planets. Like most other exoplanet discoveries, the astronomers found it by detecting the way Gliese 876 wobbles as the planets orbit the star.  We had a model for the 2 planets interacting with one another, but when we looked at the difference between the two-planet model and the actual data, we found a signature that could be interpreted as a third planet. The third planet appears to whip around the star once every 46.5 hours. The discovery was possible thanks to a recent upgrade on the high-resolution spectrometer of the Keck Observatory telescopes in Hawaii. This improved its ability to measure a star's subtle movements. Although 3 other suspected rocky exoplanets have been reported, they orbit a pulsar rather than a stable sun. For the first time, we have evidence for a rocky planet around a normal star. Gliese 876 is a red dwarf: a small, cool star about one-third of the mass of our Sun. But the planet's surface temperatures probably exceeds 200 °C, the astronomers say, because the planet passes just 3 million kilometres away from the star, more than 10 times closer to it than Mercury is to the Sun. That probably scuppers life's chances on the hot rock, but proves that more habitable planets could be detectable. We keep pushing the limits of what we can detect, and we're getting closer and closer to finding Earths. The fact that you have a rocky planet inside two gas giants makes it look a lot like our own Solar System. The prospects of finding similar planetary systems are good, because stars like Gliese 876 are extremely common. They're all over the place :of the 400 or so stars within 33 light years of Earth, about 300 of them are in the same class as Gliese 876. The team now hopes to find rocky planets around other red dwarfs in our Galaxy.
Web resources :
• Extrasolar Planet Encyclopedia
• Arizona State University guide to extrasolar planets
• California and Carnegie Planet Search
• Hubble site

Planets news

• Meet the impossible planet. This world nestles inside a system containing three stars that, according to current theories, should have denied it the chance to develop. Konacki's planet is in the triple-star system known as HD 188753, which lies about 149 light years from Earth, in the Cygnus constellation. The star at the centre of the system is very much like our own Sun. Its planet, which is at least 14% larger than Jupiter, orbits the star once every 80 hours or so, at a distance of about 8 million kilometres, a twentieth of the distance between Earth and the Sun. 2 more stars, whirling tightly around each other, orbit the central sun at a distance that would put them between Saturn and Uranus in our own Solar System. Konacki identified the planet by watching the way in which the three stars' orbits are affected by its gravity, using the Keck I telescope in Hawaii.  The planet would be a very strange place to visit. With 3 suns, the sky view must be out of this world" says Konacki, who likens it to the vista seen by Luke Skywalker in Star Wars as he watches two suns set from his home planet of Tatooine^ref. And the discovery will certainly put planetary formation theories under pressure. Planets are thought to form from the dusty disks of material that surround young stars. Icy nuggets in the disk act as seeds that slowly accumulate enough dirt to build up into a planet. But many of the 161 candidate planets so far spotted outside our Solar System are 'hot Jupiters'. These are similar to our own system's giant planet but orbit extremely close to their sun. They could not have formed in the orbits they currently occupy, astronomers argue, because such regions would always have been too hot for an icy core to exist. Instead, theorists suggest that the planets must form in a colder area far from their stars, and then migrate inwards due to drag from remaining material swirling around the systems' centres. The trouble is that this could not have happened in HD 188753. The outer pair of stars would have beaten most planet-forming material into oblivion, leaving nothing in the cold region that could form an ice core. The remaining dust would not have extended much beyond the hotter region that spans a distance equal to that between the Earth and the Sun. This makes HD 188753 something of an enigma. The most likely answer is that the planet formed in its present orbit, without an icy core. Maybe nature found a way. One possibility is that the core could have formed from less volatile materials, such as tarry hydrocarbons. Hot Jupiters could be failed stars. So in HD 188753, the planet at the centre of the 3-star system could be a fourth potential star that just had insufficient matter to start fusing hydrogen into helium, leaving a gas giant close to the central sun. More of these unusual systems will be found. Most of the stars in our galaxy are in multiple systems; our own Sun is in a minority. Konacki is now continuing with his survey of 450 multiple-star systems to look for more surprising planets.
• black holes are the remains of collapsed stars. When they form they are generally up to 100 times the mass of our Sun. But scientists are increasingly sure that many galaxies contain supermassive black holes at their heart. They cannot be observed directly, as even light cannot escape from their gravitational hold. But astronomers can observe the intense radiation emitted by material as it is sucked into the void. X-rays are the brightest component of that radiation, emitted by matter passing close to the 'event horizon', the point of no return as you approach a black hole. As dust and gas is sucked into a black hole, it forms a doughnut-shaped disk that swirls around the centre before falling in. Friction heats up the ions and electrons in the disk to around 10,000 °C, generating X-rays in the process. Although most of the material is ultimately dragged into the black hole, some of it is spat out by the hole's strong magnetic field instead, creating 2 tight jets pointing in opposite directions. In these jets, electrons spiral through the magnetic field at close to the speed of light, generating X-rays in the same way that electrons moving back and forth in a radio transmitter generate radio waves. Astronomers predict that the disk should produce lower energy X-rays than the jets. Data collected by the Italian-Dutch spacecraft BeppoSAX between 1996 and 2001, repeatedly pointed at a black hole, called 3C273, in a galaxy 3 billion light years from Earth show that different parts of the X-ray signal varied in intensity over 2 separate timescales^ref
• black holes in our Galaxy, the Milky Way :
• in 2001 : Sagittarius A*, which is about 2.6 million times more massive than the Sun^ref.
• in 2004 : IRS 13E, just 1,300 times our Sun's mass, has been found orbiting about 3 light years away from its supermassive cousin at about 280 kilometres per second. A very bright area of the galactic core, previously thought by astronomers to be a single object, is the first intermediate-mass black hole found in our Galaxy. Using infrared observations from the Gemini Observatory at the summit of Mauna Kea on the Big Island of Hawaii, it was discovered that IRS 13 is in fact a rotating cluster of 7 stars, just 0.065 light years across. Adding data from the Hubble Space Telescope and the Chandra X-ray Observatory, they calculated from the movement of the 7 stars that they must be orbiting an intermediate-mass black hole^ef. The IRS 13 cluster has also been seen emitting strong X-rays, another tell-tale sign that it hides a black hole. Smaller X-ray emissions throughout our Galaxy suggest that there may be many mini-black holes closer to Earth that are just 1 or 2 times the mass of our Sun, but this has yet to be confirmed. The 7 stars could be the remnant of a massive star cluster that has been stripped down by the supermassive Galactic Centre. The observations may help to confirm the idea that supermassive black holes, believed to nestle at the heart of many galaxies, boost their mass by sucking up smaller black holes and stars from within the galaxy. It may also explain why so many massive stars are found in the area. As the extreme gravity around Sagittarius A* prevents stars forming from clouds of dust and gas, it is possible that these stars form farther out in the Galaxy before being dragged into place by intermediate black holes. Judging from their size and colour, the 7 stars are likely to be fairly short-lived, and so are likely to burn out before they spiral to their doom.
How do you weigh a supermassive black hole? Simply follow any surrounding clumps of matter as they circle towards their doom. Astronomers using this technique have come up with the most accurate mass measurement so far for one such monster, which turns out to be > 300,000 times as massive as our Sun. The black hole that Miller and his colleagues studied is in the centre of a galaxy called Markarian 766, about 170 million light years away from Earth. Such a giant is thought to form when smaller black holes suck up matter or collide with each other. Miller and his team looked at data from the European Space Agency's XMM-Newton orbiting X-ray telescope, which watched the black hole for just over a day in May 2001. The researchers saw three clumps of hot matter spiralling around the hole, each about the mass of our Sun. These took 27 hours to make one orbit of the black hole, at a distance of several hundred million km. That's around the same as the gap between our Sun and Jupiter, which takes a leisurely 12 years to cover the same ground. The orbit time means that these 'hotspots' must be travelling at about 32,000 km/s, or > 10% the speed of light. Previous measurements of supermassive black holes have looked at stars orbiting > 100 times farther away than the hotspots, and this substantially increases errors in mass measurements. Similar hotspots may exist close to other black holes. But it is unusual for orbiting telescopes to collect data from one object for such a long period of time, which is why the possibility has not been explored before. The researchers are not yet sure whether the hotspots are captured stars, or areas of intense magnetic activity within the dust cloud that surround the black hole. They now plan to watch the Markarian black hole with XMM-Newton for a total of seven days, to improve their picture of the beast. Black holes are staples of science fiction and many think astronomers have observed them indirectly. But according to a physicist at the Lawrence Livermore National Laboratory in California, these awesome breaches in space-time do not and indeed cannot exist. Over the past few years, observations of the motions of galaxies have shown that some 70% the Universe seems to be composed of a strange 'dark energy' that is driving the Universe's accelerating expansion. George Chapline thinks that the collapse of the massive stars, which was long believed to generate black holes, actually leads to the formation of stars that contain dark energy. It's a near certainty that black holes don't exist. Black holes are one of the most celebrated predictions of Einstein's general theory of relativity, which explains gravity as the warping of space-time caused by massive objects. The theory suggests that a sufficiently massive star, when it dies, will collapse under its own gravity to a single point. But Einstein didn't believe in black holes : unfortunately he couldn't articulate why. At the root of the problem is the other revolutionary theory of twentieth-century physics, which Einstein also helped to formulate: quantum mechanics. In general relativity, there is no such thing as a 'universal time' that makes clocks tick at the same rate everywhere. Instead, gravity makes clocks run at different rates in different places. But quantum mechanics, which describes physical phenomena at infinitesimally small scales, is meaningful only if time is universal; if not, its equations make no sense. This problem is particularly pressing at the boundary, or event horizon, of a black hole. To a far-off observer, time seems to stand still here. A spacecraft falling into a black hole would seem, to someone watching it from afar, to be stuck forever at the event horizon, although the astronauts in the spacecraft would feel as if they were continuing to fall. General relativity predicts that nothing happens at the event horizon. However, as long ago as 1975 quantum physicists argued that strange things do happen at an event horizon: matter governed by quantum laws becomes hypersensitive to slight disturbances. The result was quickly forgotten because it didn't agree with the prediction of general relativity. But actually, it was absolutely correct. This strange behaviour is the signature of a 'quantum phase transition' of space-time. A star doesn't simply collapse to form a black hole; instead, the space-time inside it becomes filled with dark energy and this has some intriguing gravitational effects. Outside the 'surface' of a dark-energy star, it behaves much like a black hole, producing a strong gravitational tug. But inside, the 'negative' gravity of dark energy may cause matter to bounce back out again. If the dark-energy star is big enough, any electrons bounced out will have been converted to positrons, which then annihilate other electrons in a burst of high-energy radiation. This could explain the radiation observed from the centre of our galaxy, previously interpreted as the signature of a huge black hole. The Universe could be filled with 'primordial' dark-energy stars. These are formed not by stellar collapse but by fluctuations of space-time itself, like blobs of liquid condensing spontaneously out of a cooling gas. These could be stuff that has the same gravitational effect as normal matter, but cannot be seen: the elusive substance known as dark matter^ref.
Some British astronomers say they have found a population of missing black holes, eating their hearts out behind shrouds of dust. An image of an obscured quasar that astronomers said they created using data combined from various sources. The object has been named AMS08. The finding solves some headaches for astronomers. This is because until now, other information suggested the existence of more growing black holes than astronomers could find. The findings suggest most black hole growth takes place in dusty galaxies. Black holes, objects so compact that not even light can escape their powerful gravity, grow by sucking up material around them. Growing black holes, known as quasars, are some of the brightest objects in the universe. They are seen by the light emitted as gas and dust spiral into the hole. Quasars lie at the centers of galaxies. It’s thought that they can consume the equivalent mass of 10-1,000 stars in a year. Astronomers believe dusty rings surround all quasars, hiding them from our view in about half of cases. Even with this taken into account, though, there seemed to be many quasars missing. Their existence was suggested by the so-called cosmic x-ray background, a constant flood of X-rays from space believed to come primarily from quasars. The astronomers found some of the missing quasars by using telescopes that examine the sky in infrared light, which allows astronomers to peer through dust clouds : this is because infrared light is less prone than visible light is to reflect off the dust and scatter away from our line of sight. Using data from NASA’s Spitzer Space Telescope, the researchers found a new group of obscured quasars. They were probably hidden behind the dust of their host galaxies themselves, rather than just the dust ring that surrounds the hole more closely. The presence of lots of dust in a galaxy indicates that stars are still forming there. Dust could also feed the black hole. The study suggests most black holes grow in short, efficient bursts at the heart of growing galaxies. Throughout cosmic history most black holes grow in the heart of dusty active galaxies, with stars still forming. The astronomers found 21 examples of these lost quasars in a relatively small patch of sky. This group is large enough to account for the X-ray background, but now it seems there are more obscured than unobscured quasars, which will be the next puzzle for the researchers to solve^ref.

Black holes news

the Universe will last for at least the next 24 billion years. A team who previously predicted that the Universe might end as soon as 11 billion years from now^ref. But the team's latest research into dark energy, calculates the Universe will last for at least the next 24 billion years^ref. The team's new calculation relies on recent observations from the Hubble Space Telescope^ref, which has found several supernovae that are moving away from us faster than any others seen before, implying that the Universe is expanding faster than we thought. Astrophysicists were puzzled when they first noticed in 1998 that the Universe's expansion was accelerating. What could possibly counteract the gravity that drags massive galaxies together? Theoreticians suggested that some unseen force, dubbed 'dark energy', could be counteracting the pull of gravity. Many models describe dark energy as a negative pressure on the Universe: unlike a gas, the pressure of dark energy actually increases as it expands. Unfortunately, dark energy has never been directly seen. In Linde's model, which relies on calculations made by Yun Wang, a cosmologist from the University of Oklahoma, dark energy has 2 sources :
• a hypothetical form of energy produced by the seething mass of particles that spontaneously appear and disappear in a vacuum
• a type of force field that is intrinsic to the fabric of the Universe and continually drives its expansion.
Physicists are still divided about the fate of the Universe. Some say it will keep expanding forever, whereas others believe that at some point in the future it will begin to contract and ultimately collapse in a big crunch. But infinite expansion is just a cosmic illusion : the duration of that expansion will ultimately be finite, so that the Universe will end in collapse. Only more observations will deliver progress on the problem, because astronomers are still unsure about how much the Universe's expansion has speeded up over time. The Supernova/Acceleration Probe (SNAP) could provide much needed data to study the light from hundreds of supernovae to track the rate of cosmic bloat, but the project is currently on hold.
• The head of NASA's exploration programme has resigned: the first casualty of a cull of senior managers set in motion by Michael Griffin, NASA's new administrator. Craig Steidle, a retired rear-admiral, was appointed to the post by former NASA boss Sean O'Keefe in January 2004. In an e-mail sent to his staff on 8 June, Steidle wrote: "Yesterday, I was offered a reassignment to another job within NASA ... which I declined. Declining the reassignment means I will be leaving NASA at the end of the month." The e-mail was leaked on the website NASAwatch.com, run by former NASA employee Keith Cowing, who says that > 50 senior managers are also being offered reassignments or resignation. Certainly most if not all of top management in human spaceflight are going. Griffin will probably replace managers with people with more hands-on experience of spaceflight operations, whom he knows through his previous career as a NASA engineer. Griffin will bring back technical leadership as well as looking after the budget : he wants a similar set-up to the Apollo days. Chesson is optimistic about the opportunity to revitalize NASA with fresh blood. Chesson learned of Steidle's resignation during a telephone conference with him on 8 June. He says that Steidle claims many other senior managers will be leaving, including Fred Gregory, the deputy administrator; Bill Readdy, who runs the Shuttle programme; Al Diaz, who heads NASA's science division; and Michael Kostelnik, who helps to manage the International Space Station programme. The timing of the purge is prompted by federal regulations, which stipulate that a new agency head must wait for 120 days before involuntary job changes can be enforced, but that employees can be told of changes after 60 days. NASA spokesman Robert Mirelson could not confirm how many people would be affected by the shake-up, but said that "these things will come out in ones and twos over the next few weeks." He added that no decision has been made about Steidle's replacement. The round of reassignments is not unprecedented. When Daniel Goldin took over at NASA in 1992, he instituted sweeping management reforms, cut bureaucracy and pushed a 'faster, better, cheaper' approach. As Steidle's e-mail said, "When a new organization gets a new leader, it is usually customary for that leader to bring in his or her own management team." Since Griffin was appointed on 13 April, he and Steidle have clashed over Griffin's plans to speed up the development of a new Crew Exploration Vehicle, due to replace the ageing shuttle fleet. Some critics had questioned Steidle's management style, which organized the exploration programme into 'spirals' that few employees understood. "It was producing nothing," says Chesson. "The system had become an aim in itself."  Cowing expects dissent among NASA's middle managers. After watching their bosses being fired, he says many might fear that they too are for the chop: "They'll be seeing Banquo's ghost in the building every day."
• 2 days of tense negotiations over Europe's spending on space have ended happily for the European Space Agency (ESA). After meeting in Berlin on 5 and 6 December, ministers from ESA's 17 member states agreed to provide 95% of the funding requested by the space agency. The agency's director-general, Jean-Jacques Dordain, describes the result as "fantastic". ESA had asked for a total of 8.8 billion (US$10.3 billion) to cover its running costs until the end of 2010 and to begin new programmes, including sending a rover to Mars and launching Earth-observation satellites. It got almost everything it wanted, with some programmes receiving more money than requested. The only disappointment was that the meeting failed to decide whether ESA should embark on a project with Russia's space agency to build a reusable, 6-man space plane. ESA wanted about 50 million to carry out a preliminary, two-year study of how ESA could be involved in building Clipper, the vehicle that Russia is proposing as a replacement for its Soyuz craft. Even without that money, the matter will continue to be discussed. We need 2 transportation systems in the world. NASA has not invited ESA to collaborate on the Crew Exploration Vehicle, the successor to its space shuttle, and this is the reason why we were proposing to be a partner on the Clipper project. Contributions to running the International Space Station and its science projects have fallen slightly short of the requested 0.8 billion. However, the amount pledged shows that Europeans are still committed to the project. I shall be able to send a very important signal to the international partners and in particular to the USA. ESA will now push for its Columbus science module, ready and waiting in Germany, to be launched on the earliest possible shuttle and connected to the space station. The budget decisions boost ESA's science programme, which will get the full 2.1 billion it requested. This translates to a budget that will go up by 2.5% a year over the next five years. And it is enough to allay fears that flagship missions would be cancelled in the face of budget shortfalls. It will also lay the foundations of the 'Cosmic vision', a roadmap for future science missions stretching to 2025 that was presented to ministers at the meeting. It gives the scientists in Europe a lot of opportunities. The science funding comes as a relief to ESA officials. In the past, the scientific programme has suffered because all member states must contribute an amount determined by their national output, or GDP. Any budget increase requires a unanimous decision by the nations. Among the optional programmes, to which member states can choose not to contribute, there was strong support for plans to land a rover on Mars. Slated for launch in 2011, ExoMars secured more money than was asked for: the mission might now be enhanced by adding more instruments or a companion orbiter. The Global Monitoring for Environment and Security programme, which aims to launch satellites and coordinate Earth observation across Europe, also received extra cash. This fuels hopes that CryoSat, the ice-watching satellite lost on launch in Oct 2005, will be resurrected for a second attempt. The 2-day meeting actually wrapped up early, because the delegates reached agreement more quickly than expected. At a time when a lot of people have doubts about Europe's capacity to act together, this was historic
• Texas astronomers have pinned down the exact date and time that a famous Ansel Adams photograph was taken. Using astronomical clues such as the position of the Moon and the length of shadows in the snap, a group from Texas State University has worked out that Adams shot Autumn Moon, the High Sierra from Glacier Point at 19:03 (2:03 GMT) on 15 September 1948. In a travelling exhibition, currently in California, the photograph is dated to 1944. Although Adams took detailed notes on the exposures for his works, he was often frustratingly vague about when and where the shots were taken. But Adams's love of sky phenomena, particularly the Moon, sometimes provides enough clues for a little astronomical sleuthing. The Moon with its rapidly changing phases and position is really a big cosmic clock. When you've got a picture with a Moon in it, you can do these calculations. In 1991, di Cicco pinpointed the time and place of Adams's iconic Moonrise, Hernandez, New Mexico. Inspired by that work, in 1994 Olson's team tackled Moon and Half Dome, taken in Yosemite National Park in California, and then moved on to Autumn Moon. The Moon is clearly on its way to becoming full in the picture. And its position above the mountain peaks helps to narrow down when the shot could have been taken. Less obviously, a close look reveals that a dark region near the Moon's north pole, called Mare Frigoris, is captured in the snap. Although the Moon always keeps one side roughly facing the Earth, it does wobble a bit, so the position of this dark patch helps to restrict the possible dates. The astronomers then unearthed a rare colour version of Autumn Moon, which appeared in Fortune magazine in 1954. From the position of the Moon they could tell that the colour image must have been taken first, and the black-and-white version just over two minutes later. By looking at shadows in the two, the team pinpointed the altitude and azimuth of the sun, to further determine the timing of the photo. The researchers verified their theories with a trip to Yosemite in June, during which they confirmed where Adams took the shot from, as well as measuring the distances to the mountains and the Moon's location from there. Adams took the photos from near a stone building called the Geology Hut atop Glacier Point, the team reports in the October issue of Sky & Telescope. The colour image was taken at 19:01, and the black-and-white version at 19:03. The celebrated photographer captured a unique glimpse of the High Sierra in those brief moments, says Olson. There are just a few minutes when you can capture both detail in the Moon and the last shadows cast by the setting sun. Getting the balance of all that is very hard to do, and Adams knew how to do it. On 15 September 2005, celestial events will coincide to recreate the dramatic lighting seen in Autumn Moon. The Texas State group plans to be there to witness the scene that Adams captured 57 years ago.

Web resources : Sky and Telescope magazine

Web resources :

• American Astronomical Society (AAS)
• European Space Agency (ESA)
• National Aeronautics and Space Administration (NASA)
• Russian Aviation and Space Agency (PKA)
• Russian Academy of Science (RAS)
• Japanese Aerospace Exploration Agency (JAXA)
• Encyclopedia of Astronomy and Astrophysics
• Committee on Space Research
• Royal Astronomical Society meeting
• Yuri's night
• International Virtual Observatory Alliance (IVOA)



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