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Nasa's Mars Curiosity rover finds no sign of methane, the gas linked to life Nasa's Mars Curiosity rover finds no sign of methane, the gas linked to life
(about 1 hour later)
Nasa's Curiosity rover hasn't discovered any signs of methane in the atmosphere of Mars, a finding that does not bode well for the possibility that microbes capable of producing the gas could be living below the planet's surface, scientists said Thursday. Hopes that microbial life might be found on Mars looked a little dimmer on Thursday night after Nasa announced that its Curiosity rover had found no traces of methane in the tenuous atmosphere of the Red Planet.
Since landing in Gale Crater last year, the car-size rover has gulped Mars air and scanned it with a tiny laser in search of methane. On Earth, most methane gas is a byproduct of life, spewed when animals digest or plants decay. The 900kg rover has been searching for evidence that the planet was once habitable since it touched down in the ancient Gale crater on Mars in August last year.
Curiosity lacks the tools to directly hunt for simple life, past or present. But scientists had high hopes that the rover would inhale methane, after orbiting spacecraft and Earth-based telescopes detected plumes of the gas several years ago. Persistent levels of methane in the atmosphere on Mars could have been a sign that living microbes lurked deep beneath the rock and dust, but the absence of the gas will deflate hopes that they are there to be found.
"If you had microbial life somewhere on Mars that was really healthy and cranking away, you might see some of the signatures of that in the atmosphere," said mission scientist Paul Mahaffy. On Earth many microbes release methane as a waste product that mixes in the atmosphere with substantial contributions from cows, pigs, and humans. But not all microbes are methane makers. The majority release other gases instead.
During Curiosity's first eight months on the red planet, it sniffed the air during the day and at night as the season changed from spring to summer. "The measurements we've made show that microbial activity from methane-producing microbes is insignificant on Mars," Nasa scientist Chris Webster told the Guardian.
"Every time we looked, we never saw it," said Christopher Webster, of Nasa's Jet Propulsion Laboratory, who led the research published online in the journal Science. "But there are other microbes that do not produce methane, so there remains a possibility that there is subsurface microbial activity that is not emitting the gas," he added.
Webster said while the result was "disappointing in many ways", the hunt for the elusive gas continues. While methane is linked to living things, it can also be made by non-biological processes. Webster, who is head of the team that ran the analysis at Nasa's Jet Propulsion Laboratory in Pasadena, California, said it was too soon to call off the hunt for alien organisms on the planet.
Michael Mumma of Nasa's Goddard Space Flight Center previously noticed a mysterious belch of methane from three regions in Mars' western hemisphere. Mumma, who had no role in the latest study, said he stood by his observations. "The search for life on Mars is far from over. It takes two particular efforts. One is to look for current microbial activity. But the other is to analyse the rocks to look for signs that the conditions were once right for life. And we are doing that now."
Earlier this month, Curiosity reached its first rest stop in its long trek toward Mount Sharp, a mountain rising from Gale Crater near the equator. The rover will take monthly readings of the Martian atmosphere during the road trip, expected to last almost a year. "There was a period on Mars when there was water on the surface, a rich diversity of chemicals, and we've seen evidence of lake beds and ancient rivers, so there remains the possibility that the conditions were conducive to the existence of life long ago," he said.
Curiosity previously found evidence of an ancient environment that could have once been suitable for microscopic life. Scientists still hope to uncover signs of organic molecules, considered the chemical building blocks of life, at the base of Mount Sharp. The results appear to contradict previous studies that claimed to have found traces, and even occasional, giant plumes of methane emanating from the Martian surface. In 2009, Nasa held a press conference at its headquarters in Washington DC to announce it had found belches of methane around several geological features on the planet.
Scientists used an instrument onboard Curiosity called the Tunable Laser Spectrometer to take measurements of the Martian atmosphere. The results showed no signs of methane. If it is there at all, it must be in feeble concentrations of no more than 1.3 parts in a billion, the scientists write in the journal Science.
Had Nasa completely ruled out life on Mars it would pose problems for the European Space Agency, which plans to send its own alien-hunting rover to Mars in 2018. Unlike Curiosity, the ExoMars rover will be equipped to look for existing life on the planet.
Webster said the European mission should not be threatened by Nasa's latest results. "The ExoMars mission is a very powerful mission. It's not focused on methane mapping. It's looking at the entire inventory of the chemicals in the atmosphere on Mars," he said.
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