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Mars Express

Europe's space program takes a step forward—in science and prestige.

By Robert Kunzig and Ferit Kuyas
May 1, 2003 5:00 AMNov 12, 2019 4:17 AM
In a clean room in Toulouse, France, scientists from Austria and Germany run through test after test of the Mars Express orbiter. The Beagle 2 lander, which has not yet been attached to the spacecraft, is a big worry because if it fails to separate from the orbiter as the package approaches Mars, both will be lost.


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One morning last September in Toulouse, France, Antonio Rodotà, director general of the European Space Agency, stood in front of a crowd of reporters who had flown in from all over Europe to gather in a cavernous hangar. The floor of the hangar was covered with a red carpet, and the pretty young hostesses who handed out the press kits were wearing bright red dresses. Moments earlier, to a sound track of sopranos floating over driving electronic rhythms, a large door on the reporters' left slid open, unveiling a full-scale mock-up of Mars Express — the spacecraft ESA plans to launch in late May or early June.

The model was suspended from the roof of the darkened hangar and bathed in nocturnal blue light. As the music swelled, spotlights caressed the model's extended solar panels and its large, steel gray radio dish. They then turned to illuminate two bright red Ferraris. One was a Formula 1 race car. A photo of Mars floated like a rust red moon on the far wall of the hangar. ESA was calling this event the Red Encounter.

Rodotà, a genial, gray-bearded, distinguished-looking Italian, stood onstage with other European space dignitaries, looking a bit ill at ease. He and everyone else in the hangar were wearing floppy disposable overshoes; later they would put on hairnets and lab coats and shuffle into a nearby clean room. There they would watch and snap pictures as Rodotà and ESA's science director, David Southwood, supervised the attachment of a vial of Ferrari-red paint to the underside of the real Mars Express. Thus, if all goes well, the paint, too, will enter Martian orbit next December. Rodotà had the unenviable task of explaining all this.

"Why are we here today?" he began. "Why this strange joining of cars and satellites?" Ferrari, he acknowledged, did not need the publicity; it was ESA that was basking in Ferrari's red glow, trying to link its own feats of engineering in the public mind with sexy race cars. Not only are Europeans far more familiar with Ferrari than with ESA, Rodotà pointed out, they are also more familiar with NASA: A 1998 poll showed that 54 percent of them knew about the American space agency, but only 10 percent had heard of their own. The ratio of those two numbers, he added sardonically, is about the same as the ratio of the two space agencies' budgets — NASA's is five times larger, even though the collective gross domestic product of ESA's 15 member states is close to that of the United States. That poll had made Rodotà realize that his agency must work quite a bit harder at public relations.

NASA, in the aftermath of the shuttle tragedy, has all the public attention it needs. But ESA deserves far more than it gets. With a science budget of around $350 million a year, less than the cost of a single space shuttle launch, Southwood runs an ambitious program. Last October ESA launched a gamma-ray telescope called Integral as a companion to its successful X-ray telescope XMM-Newton, already in orbit. Over the next decade, the agency plans to launch infrared and microwave telescopes as well. ESA also intends to send spacecraft to Venus and Mercury, which are not even on NASA's schedule. Even more amazing, it plans to land a probe on a comet. 

Mars Express will be the first spacecraft Europe has sent to another planet. When it lifts off on a Soyuz rocket from Baikonur, Kazakhstan, it will be carrying a German stereo camera capable of taking 3-D images of most of the surface of Mars. It will carry Italian radar to probe far beneath that surface for possible hidden reservoirs of water. And just before it arrives, it will jettison an ingenious, suitcase-size lander called Beagle 2. Built by British scientists who had to take out a loan to finance it, and were still working nights and weekends to finish it only weeks before launch, Beagle 2 could scoop NASA on a huge question: Did life ever exist on Mars?

In the hall outside Southwood's office at ESA headquarters in Paris, there are lots of photos of technicians in hairnets contemplating gleaming spacecraft that have long since been launched. On a credenza a few steps away, there is something more unusual: a crumpled titanium cone mounted like a sculpture on a stone pedestal. The brass plaque on the pedestal reads: "Cluster F1, Main Engine, Recovered Kourou, June 1996." It's a souvenir of the first launch of the French Ariane 5 rocket in Kourou, French Guiana, and a reminder of how far the European space program has come. 

Cluster—four identical spacecraft designed to fly in formation—was a mission like no other. And it still is, because the replacements were launched in 2000 and are studying the auroras and other phenomena triggered by the solar wind. Southwood, then a space physicist at Imperial College in London, was at Kourou on June 4, 1996; he had been dreaming about the mission for 30 years. ESA was taking the risk of launching it on Ariane 5's maiden flight. 

Rudi Schmidt, an Austrian space physicist who is ESA's project manager for Mars Express, was the project scientist for Cluster. Like Southwood, he was at Kourou when the rocket lifted off on the morning of June 4. The champagne was already on ice inside. Schmidt was 47 in 1996 and had been working on Cluster since he was 34. 

For the first 30 seconds after liftoff, everything was fine. "We saw the launcher disappear behind a cloud," he says. "Then we heard a funny kind of sound—a soft boom. And we didn't see the launcher coming out of the cloud." He ran inside and looked at the television monitors; they showed flight controllers with their heads in their hands. He ran outside again just in time to see a fireworks of Ariane 5 and Cluster parts raining down from the sky. 

Had there been people on that rocket, the loss would have been incomparably greater. And yet, when you have put your heart and so many of your waking hours into a piece of machinery only to watch it explode before your eyes, it can feel like a death. To this day, Southwood doesn't like going to Kourou: "I'm still haunted a bit by the experience." 

Failure is familiar to space scientists—especially Mars scientists. Russia, in 35 years of trying, has never completed a successful mission to Mars. NASA has alternated between triumph and disaster. In 1993 it lost a billion-dollar spacecraft called Mars Observer; partly in response, NASA switched to a strategy of not putting all its eggs in one basket, a strategy summarized by administrator Dan Goldin's now-famous slogan "Faster, better, cheaper." The 1997 Pathfinder was a total triumph; its little rover, called Sojourner, captured the public imagination as few spacecraft have since the moon landings. 

But the next two missions, in 1999, were total losses. Mars Climate Orbiter went off-course and burned up in the Martian atmosphere because navigators were using English units while the spacecraft itself was using metric ones. Mars Polar Lander probably crashed into Mars, but no one can be sure; to save money, the spacecraft had been denied the ability to communicate with Earth during the landing phase. Faster, better, cheaper had gotten too cheap, and the testing that might have caught mistakes before launch had been neglected. It is a lesson no one embarking toward Mars can avoid meditating on. 

"You cut corners," said Southwood one Friday afternoon last November, sitting at the conference table in his corner office. He is a tall man with thick gray hair and a mustache, a candid baritone, and a taste for double-breasted suits. He likes America, having spent a few years at the University of California at Los Angeles; he cooperates with the American space program every day on all sorts of joint missions. He also competes with it. It is his benchmark, he says. On his table there is a doorstop of a book called The Century of Space Science. The 20th was the American century, and Southwood would rather the current one were not. His own slogan, pointedly, is "Faster, smarter, cheaper." 

"You pushed people too hard," he continued. "If you work with a limbo bar that's going down, you really have to take a look beforehand to see that the guy who has got to go under the limbo bar is physically capable of it. You can't simply declare: You will save such and such. 

"Building a spacecraft is not building a spacecraft; it's building and testing and testing a spacecraft, because you can't go up and fix it. You can always ask: Can you do the tests more efficiently? But what you mustn't do is just tell some guy who's got a set of procedures, 'OK, reduce the procedures by 10 percent.' If you don't analyze how you're going to do it—that's what I mean by 'smarter'—clearly there's a high risk." 

ESA was under even more pressure than NASA to be cheap when it finally decided, in late 1996, to go to Mars. Marcello Coradini, a short, bespectacled, and good-humored Italian who is ESA's solar system mission coordinator, was instrumental in the decision. Earlier that year, the agency's Space Science Advisory Committee had vetoed yet another proposal of his for a mission to Mars, preferring to spend money on orbiting telescopes and on relaunching Cluster. Coradini's constituents, the planetary scientists of Europe, were upset. The agency had never funded a mission to another planet. Some scientists, as a result, were participating in a Russian mission called Mars 96. In addition to its homegrown payload, it carried several hundred million dollars' worth of instruments built in France and Germany. On November 16, 1996, Mars 96 was launched on a Proton rocket from Baikonur. It disappeared downrange in a satisfying way, and the scientists headed for the airport. Then the fourth stage of the rocket failed to fire, and Mars 96 fell into the Pacific. 

At a meeting of the SSAC that December, with the gloom still deep, Coradini seized the day. He knew the scientists who had built instruments for Mars 96 had spares; that's standard procedure in space science. "I said, 'Look, gentlemen, Mars 96 is lost. Why don't we put together a fast mission, with a simple spacecraft and all these spare instruments, and launch it to Mars?' I said it almost as a provocation. 

"There was a moment of silence. And in about 25 seconds, the committee said, 'This is a great idea, we should do it!'" Coradini laughs gleefully at the memory. "I stared at them and said, 'What? Are you serious?'"  The constraints certainly were serious. The instruments were mostly ready and paid for, but given ESA's other commitments, the spacecraft would have to be built, launched, and operated for $150 million. And it had to be done fast, because the best launch opportunity in decades is this month, as Earth passes Mars at perihelion, when the two planets are closest to the sun and to each other. That gave them only six years, whereas the usual gestation period for a scientific spacecraft is more than a decade. 

"So I went to John Credland," says Coradini, "who is responsible for spacecraft construction at ESA, and I said, 'John, you got to do some magic here.' And he had this brilliant idea." If much of the payload of Mars Express was being recycled from Mars 96, much of the spacecraft itself could be recycled from the comet-chaser Rosetta, which also had a launch date of 2003 and was already under construction. Just as space scientists always build spares of their instruments, the makers of the spacecraft itself build spares of subsystems—propulsion, attitude control, electric power, communication, and data handling. Credland realized those spares could be taken off the shelf, modified, assembled into a box, and flung at Mars. Suddenly, six years seemed feasible.  Next ESA cut out layers of bureaucracy, giving far more responsibility than it had before to the prime contractor—in this case Astrium, the aerospace giant based in Toulouse—and limiting Rudi Schmidt's staff to a dozen or so engineers. "The design period was fast and short and crisp—that saves money," says Schmidt. "But then we do so much testing that we're sure we still have a good spacecraft." ESA has another guarantee, he adds. Astrium gets its last payment only when the spacecraft achieves orbit around Mars. 

Astrium has another incentive to get it right: It is already at work on Venus Express, which will be assembled mostly from spare components of Mars Express and is scheduled for launch in 2005. Southwood has taken the idea Credland had for Mars Express and pushed it to the hilt. His whole program is now organized into production groups, in which each expensive flagship mission, such as Rosetta—which cost $750 million—has at least one cheaper spin-off. The Mars mission is the first test of this fundamental strategy. "It's fast, it's cheap; that's why it's called Mars Express," says Coradini. "And it's beautiful—if everything goes well." He crosses his fingers and laughs.

If everything goes well, Mars Express will tell us where all the planet's water has gone. Like Earth, Mars must have received a lot of water at birth; some researchers think the plains that cover most of its northern hemisphere were once the bed of a vast, shallow ocean, filled by cataclysmic floods of water cascading out of the southern highlands. As Mars Express flies in polar orbit, dipping to within 155 miles of the planet spinning beneath it, instruments made in Sweden, France, and Italy will map the composition of the atmosphere, looking in part for evidence that vestiges of that water are still escaping into space. An infrared spectrometer built by Jean-Pierre Bibring of the Institute of Space Astrophysics in Orsay, France, will make a mineralogical map of the planet's surface, looking in part for the carbonate sediments that should have been deposited in Martian lakes or oceans. Finally, ground-penetrating radar designed by Giovanni Picardi of La Sapienza University in Rome will attempt to probe the frozen Martian crust to depths of two to three miles, looking for water ice or even liquid aquifers. Last year scientists operating a gamma-ray spectrometer on Mars Odyssey, the NASA spacecraft launched in 2001, reported indirect evidence of large amounts of hydrogen, presumably in the form of water, in the upper few feet of Martian soil. Picardi's instrument may greatly expand on that evidence. 

It is the two remaining instruments, however—the stereo camera and Beagle 2, the British lander—that are most likely to enchant the layman. Sitting at an outdoor café in Toulouse, Gerhard Neukum, a bald, stocky planetary scientist from the Free University of Berlin, explained the many virtues of the camera he built—starting with its sex appeal. "You can't sell particles-and-fields measurements to the public," he said. "With a camera, you see a landscape on Mars and you can say, 'This is it.' It doesn't matter what it means. You see dunes, volcanoes, dry riverbeds, ice—people understand that." 

Neukum started working on his camera in 1988, and before Mars 96 came along, he was hoping it would fly on Mars Observer. NASA instead chose a camera built by Michael Malin, now of Malin Space Science Systems. After Mars Observer failed, Malin's camera went into space in 1997 on Mars Global Surveyor, and it is still sending back spectacularly detailed pictures. In 2000, for instance, Malin published pictures of small gullies that, judging from the absence of meteorite craters in them, seem to have been formed by running water within the past few million years. People used to think Mars had dried up billions of years ago; Malin's camera has rejuvenated Mars. 

Malin delivered the sharpest pictures of Mars ever: Each image covers roughly a square mile; each pixel—at maximum resolution—an area five feet across. But Mars Global Surveyor is surveying less than 1 percent of Mars in such detail. The images are like scattered postage stamps on the Martian map, Neukum says, and because the global photographic coverage is so crude, Malin's gullies and other fine features can be situated to within only five miles or so. Neukum's camera is designed to fill that gap. During the two-year mission of Mars Express, it will survey more than half the planet at a resolution of 30 to 50 feet; if the mission is extended to four years, he says, he can do the whole thing. 

Neukum's pictures will be in stereo and in full color—whereas the detail shots from Mars Global Surveyor are flat and black-and-white. In Neukum's camera, the CCD light sensors are arrayed in nine parallel lines, each one 5,184 pixels long by a single pixel wide and all of them perpendicular to the direction of flight. The center line will look straight down, while the back line will be angled slightly forward and the front line slightly backward. Thus, as Mars Express streaks over Mars at two-and-a-half miles per second, the three lines will record a given point on the surface from three different viewing angles—"it's as if you had three eyes, not just two," Neukum says—and those records will then be melded into a 3-D image that will reveal the precise height and shape of the land below. Meanwhile, the other six lines of sensors will record the brightness and full color of the scene, with one line each for red, green, blue, and infrared. Right now there are almost no true color pictures of Mars, Neukum says: Because of the spectral limitations of previous cameras, nearly all the color images you've seen have involved some degree of fakery or interpretation. 

What the public can imagine doing in a few years, if Neukum's camera works, is donning a pair of 3-D glasses in a movie theater to go on an aerial tour of Mars. What Neukum imagines doing is unraveling the geologic history of the planet—including the history of its water and the question of whether it ever had enough, long enough, for life to evolve. Some top American Mars experts, he notes with pleasure, have joined the team that will analyze his images. "Malin's camera was good, but I want to beat him," Neukum says. "This will be the best experiment ever for Mars, or for any planet. I'm not exaggerating." 

One person who might argue the point is Colin Pillinger. Pillinger, a chemist at the Open University in Milton Keynes, England, is the man behind Beagle 2. Recent photographs show him bent over his contraption, with a big, devilish grin. A year from now he may have more to grin about. If Beagle 2 finds evidence of life on Mars, no other result from Mars Express, or from any other planetary mission, will compare with it.

The question of life returned to the center of the Mars discussion in August 1996, when NASA held a press conference about a meteorite called ALH 84001. Everyone agrees it is one of a few dozen meteorites that we know came from Mars; it was bounced off that planet by a larger meteorite 16 million years ago and eventually fell onto the Antarctic ice. But at the press conference in Washington that day, NASA scientist David McKay and his colleagues announced something even more amazing: They had found several signs of fossil life in the rock, including what to them looked like fossilized bacteria. The debate about whether they were right rages on. The stakes are considerable—even a few fossil microbes on Mars would shatter our lingering conceit that Earth might be unique in the universe as a haven for life. It would even lend support to the recent and bizarre hypothesis that Earth might have been seeded, billions of years ago, by microbe-bearing Martian meteorites. 

Pillinger himself has long been convinced that evidence of life on Mars exists. In 1989 he and his colleagues Ian Wright and Monica Grady reported finding carbonate sediments and organic matter in another Martian meteorite called EETA 79001. Their claim was especially surprising because EETA 79001, like all Martian meteorites, is a volcanic rock, in which you wouldn't expect to find sedimentary material. 

"The whole mineralogical community did a wobbly," Pillinger recalls. "They said, 'You can't have carbonates in these rocks.' It's real Doubting Thomas stuff, this—'I've got to put my finger in the hole, otherwise I'm not believing you.' That's the whole story of Martian meteorites all the way along." 

After the NASA press conference, Pillinger and his colleagues repeated their analysis of EETA 79001. They had already done the same experiments on a sample of ALH 84001. They found evidence of carbonates in both rocks, and organic matter in EETA 79001. There was one important difference between the two, however: Whereas ALH 84001 had crystallized from volcanic lava on Mars 3.6 billion years ago, EETA 79001 was only 180 million years old. Thus, if Pillinger's group was right, there was evidence of life on Mars in the relatively recent past, geologically speaking. 

In late 1996, Pillinger, who had not been involved in Mars 96, heard about an upcoming meeting in Paris to discuss a replacement mission. He got himself invited. "And while they were talking about who had spare instruments," he recalls, "I said 'Look, everything's moved on, guys. You really have to think about a lander, because there's all this stuff going on with Martian meteorites.' The immediate response was, 'Who's going to pay for it?' I said, 'Good God, this is so important! It would be stupid to go to Mars in 2003'—after all, America was now working on Pathfinder and a whole suite of follow-ups—'with just an orbiter. Somebody will pay for it,' says I." 

Pillinger has been chasing that elusive somebody ever since. Early on, he and the other scientists involved agreed to work on the lander on the side, with no additional research funds—"Marslighting," they called it. Belatedly, he got a large chunk of money from the British government and a larger one from the ESA. But the final contribution was a mysterious loan that Pillinger is committed to repaying through commercial sponsorship—though as the launch date approached and no deal was concluded, the world was spared the sight of the first corporate logo on another planet. 

Beagle 2 is innovative in important ways. The main argument of the Doubting Thomases has always been that the chemical signs of fossil life in Martian meteorites are really terrestrial contaminants; perhaps microbe-laden water seeped into cracks in the rocks after they landed on the Antarctic ice. Beagle 2 is an effort to settle that debate by transporting Pillinger's laboratory to the surface of Mars—in miniature form, of course. ESA won't allow it to weigh more than 22 pounds. 

That eliminated the possibility of imitating NASA. Early next year, not long after Beagle 2 arrives, NASA plans to land another two rovers on Mars. Each will weigh 300 pounds. One of their primary goals is to look for the sort of sedimentary rocks that a future spacecraft can bring back to Earth for analysis. NASA has set a date of 2014 for the sample-return mission—but other than that, says Pillinger, its strategy is perfectly valid, and he wishes ESA had the budget to emulate it. But with a total launch mass of just over a ton, Mars Express has no room for a rover. Beagle 2 will try to decide whether there has ever been life on Mars without budging from its landing site. "We have one shot at this," Pillinger says. "And we have technology that is capable of answering the question on the first shot." 

The design that Pillinger and his colleagues came up with, "on the back of the proverbial beer mat" at a bar in Toulouse, looks like a pocket watch—a three-foot-wide pocket watch. Perched on top of Mars Express for the journey from Earth, the lander will separate from the mother ship about five days before arrival on Mars. Parachutes will slow its descent through the atmosphere; air bags will cushion its fall onto the rock-strewn floor of a vast impact crater called Isidis Planitia.

After the air bags deflate, the pocket watch will pop open. When the motorized hinge drives the two halves of the watch apart, its inner works will face upward into the thin Martian air. Four solar panels will flop open and start generating power. A 32-inch-long robotic arm will then probe the immediate environment. 

Most of Beagle 2's instruments will be splayed like a fan at the end of that arm. Stereo cameras will look for interesting rocks; a microscope will reveal their texture; gamma-ray and X-ray spectrometers will determine their composition. A rock corer will grind away at the surface of the rock, while an ingenious instrument dubbed the Mole, designed by a team led by Lutz Richter of the German Aerospace Center in Cologne, will burrow into the soil. The Mole is a metal cylinder, four-fifths of an inch in diameter, at the end of a tether. Inside is a spring-loaded hammer, powered by an electric motor that drives the device forward by pounding into the soil. "It's not a very elegant motion," says Richter. "Every five seconds you have a shock, and it moves one centimeter." But the Mole can dive to a depth of six feet and return with .0021 ounce of Martian soil trapped in the chamber at its tip. 

The purpose of both the rock corer and the Mole is to recover pristine samples that have not been exposed to the oxidizing Martian atmosphere, because oxidation destroys organic matter. To people who believe there may once have been life on Mars, this is why the Viking landers in the 1970s found no evidence of it: They scooped samples only from the top few inches of soil. Beagle 2 will probe deeper, and the six or eight samples that the robotic arm brings back to the body of the lander will undergo a deeper analysis than Viking was capable of, the same analysis Pillinger's team has used on Martian meteorites. In this process, called stepped combustion, the sample is burned at progressively higher temperatures; the temperature at which the carbon escapes reveals the nature of the compound. 

A mass spectrometer will detect every single carbon atom that wafts off the burning sample, says Pillinger, and even whether it is C-12 or the heavier isotope C-13. Living organisms on Earth selectively concentrate C-12 in their tissue. If Pillinger's device detects organic compounds that have more C-12 than do inorganic carbonates in the same sample, that will be strong evidence that life was once present. Even if it was just a few microbes deposited by a trickle of water in a chunk of lava, Pillinger thinks he will be able to detect the signal. He doesn't need to find sediment laid down by plankton at the bottom of some warm little pond.  On the other hand, he will only get to look at a few small samples from one single site. "We have to get lucky," he says. 

There are so many ways that things could go wrong. Things could go wrong even if Mars Express and Beagle 2 work exactly as planned. They could find little water and no evidence of life, past or present. Some people would be terribly disappointed by that. It has happened before: For 30 years, until the renaissance triggered by ALH 84001, we had to scale back our expectations of Mars. In 1965, when Mariner IV arrived, it found craters instead of canals, dry ice, and a pitifully thin atmosphere. A decade later, the Viking landers drove another nail into the coffin. "The reality that Mars is probably dead is still so hard to accept," NASA planetary scientist Kevin Zahnle wrote recently, "that revivification remains the central thrust of NASA's unmanned exploration program." 

Things could go wrong at every step of the way. Beagle 2 could crash on a rock, or it could land too far from a rock to sample it with its short arm. The pyrotechnic devices designed to separate it from Mars Express could fail, in which case the spacecraft itself would be too heavy to achieve its intended orbit, and the whole mission would fail. And things could go wrong as early as the launch. Last October, a Soyuz rocket similar to the one that will carry Mars Express exploded at launch. The next launch, carrying cosmonauts to the space station, was successful. Then in December, a new, heavyweight version of Ariane 5 failed right after blasting off from Kourou. Southwood and officials at Arianespace, the launch company, decided to call off the January launch of Rosetta on an old-style Ariane 5. Nobody wanted to risk another Cluster, another 1996. "It's not so long ago, but it seems like ages," says Coradini. 

On his office wall in Paris there is a poster, a picture of a crescent moon with the words "Nothing Happens Unless First a Dream." It's a greeting-card sentiment, easily mocked, but the more you learn about a spacecraft like Mars Express, the more you appreciate how many dreams and how many people are exposed in it. The scientific instruments come from Britain, Germany, France, Italy, and Sweden. The antenna was built in Spain, the solar panels in Germany, the spacecraft structure in Switzerland. The parts were assembled in Italy, and the software was installed in France. "It's not the most efficient way of doing things," says Schmidt. "But this is how we have to do it in Europe." If Mars Express succeeds, all those Europeans can look forward to a future of exploring other planets. If not, maybe not.

Faster, Smarter, Cheaper 

The heart of Mars Express is a five-foot-long, gold-foil-covered aluminum box of six experiments and a lander. Course corrections on the way to Mars will be managed by eight small auxiliary engines at the corners of the box. The main engines (bottom left) will be used for corrections once the craft is in orbit around the Red Planet. A six-foot-wide dish antenna will receive instructions from Earth ground stations. Experiments aboard include:

1. ASPERA—sensors that detect and identify atoms, ions, and electrons in Mars's outer atmosphere as well as in the solar wind, consisting of particles rushing at the planet from the sun. Scientists suspect water on the surface of Mars evaporates, rises into the upper atmosphere, breaks into hydrogen and oxygen atoms, and is then swept into outer space by the solar wind.

2. SPICAM—two spectrometers that examine Mars's atmosphere at wavelengths slightly shorter and slightly longer than visual light. The ultraviolet detector determines how much ozone the atmosphere has, and the infrared detector measures how much carbon dioxide and water vapor there is in the atmosphere.

3. PFS—a spectrometer to determine what gases and dust particles occupy Mars's atmosphere. Designers are hoping to detect trace amounts of complex molecules such as formaldehyde and to measure changes in the atmosphere that vary with altitude. A more complete understanding of Martian weather should emerge from these studies over time.

4. Beagle 2—a lander that unfolds on the surface, then begins searching for signs of life. Sensors are designed to examine radiation, gases, and dust. A self-burying probe will dig itself down as far as six feet to recover small samples of soil that are more likely than oxidized surface dust to contain life. Cameras will send back 3-D images. X-ray and gamma-ray spectrometers will analyze nearby rocks.

5. OMEGA—a visible-light camera and infrared spectrometer intended to map and identify minerals on the surface of the planet. The instrument is designed to work with the HRSC and PFS instruments if and when especially intriguing surface features are identified.

6. HRSCa high-resolution camera that can make full-color 3-D images of large swaths of Mars's surface. The camera can also zoom in for a closer look and may be helpful in identifying useful landing sites for future Mars missions.

7. MARSIS—ground-penetrating radar that should be able to determine the composition of Mars's crust to a depth of several miles. It should also be able to measure interesting local geology such as sand dunes, lava flows, sediment left by ancient rivers, and underground reservoirs of water.

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