Europe is to launch its most ambitious space mission yet, to seek out life on Mars — by detecting the waste gases of subterranean microbes.
Next week, the European Space Agency (ESA) will launch the Trace Gas Orbiter, a probe designed to analyse the Martian atmosphere for emissions of methane and work out just what is producing them.
The mission is the first stage in the ESA’s ExoMars programme. The second, in two years’ time, will see the ESA flying a British-built robotic rover to the Red Planet’s surface, where it will drill 7ft down into the Martian crust to try to locate some of the methane-producing microbes.
“These missions are specifically designed to see if life has ever existed on Mars and if it still survives,” said Professor Andrew Coates, deputy director of University College London’s Mullard Space Science Laboratory, who is closely involved with the project.
“Methane is one of the key gases we are looking for. We know from other missions that it is coming from under the surface, and there are only two possible sources: geothermal activity or, mind-blowingly, some form of life, almost certainly microbial.”
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“The question is whether life, or its remains, might persist underground
Scientists and science-fiction writers have speculated about life on Mars for centuries, but it was only recently that space probes sent to the planet produced tantalising hints that they could be right. Some of the evidence comes from Nasa’s Martian rovers, which found soil and rocks that could only have formed in lakes or rivers, suggesting the Red Planet was once at least partly blue.
Other measurements show Mars also once had a magnetic field that protected it from the sun’s searing radiation, as the Earth’s does today.
“The emerging picture is that soon after Mars formed, around 4.6bn years ago, it was a very suitable place for life,” said Coates. “But about 3.8bn years ago its magnetic field died, allowing solar radiation to strip away its oceans and atmosphere. The question is whether life, or its remains, might persist underground.”
The strongest evidence for this comes from observations made by Nasa’s Curiosity rover and from Earth-based telescopes, suggesting there is methane in the Martian atmosphere — but the levels of just a few parts per billion are too low for scientists to be sure.
Hakan Svedhem, the ESA’s project scientist for the Trace Gas Orbiter, said: “We have detected methane on Mars already but its behaviour is very strange — the levels go up and down, suggesting something is making it but something else removes it.”
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The orbiter will also map deposits of underground ice and water, but its instruments alone will not be enough to give final proof of life — so the ESA plans to follow it with the ExoMars rover, a buggy the size of a golf cart, which will launch in 2018, specifically equipped to seek out buried microbes.
Rolf de Groot, head of the ESA’s robotic exploration programme, said the Trace Gas Orbiter would also carry an experimental lander, called Schiaparelli, which will test out the landing technologies needed to put the rover and a separate Russian instrument package safely onto the surface of Mars.
“This will pave the way for the rover, where the biggest innovation is the drill,” he said. “This will allow us to reach the soil layers where microbes might still survive. The samples it drills from the ground will be analysed by an onboard laboratory looking for the molecules of life, such as amino acids, lipids and nucleotides.
“The anticipation and ambition is huge. We are trying to answer one of the biggest questions in science: is there life on other planets?”
Britain is among the lead countries on the ExoMars programme, contributing £163m of the ESA’s £1bn budget for the project. The rover is being built in Britain at the Airbus space facility in Stevenage.
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There is, however, a downside to discovering life on Mars: it could jeopardise the ESA’s most ambitious plan of all — to bring samples back from Mars — by raising fears of infecting our home planet.
De Groot said: “If ExoMars finds life then our plans become far more sensitive and we will have to consider strict planetary protection protocols to minimise that risk.”