[Audie Cornish:] Something intriguing is happening on Mars. Instruments onboard the rover known as Curiosity are seeing bursts of methane entering the Martian atmosphere and then disappearing. NPR's Joe Palca reports.
[Joe Palca, Byline:] Scientists have been eager to search for methane gas on Mars, because although methane can be produced by simple inorganic chemistry, another way you can get methane is for living microbes to make it. The first measurements Curiosity made after it landed in 2012 seemed to indicate there was almost no methane at all in the Martian atmosphere less than one part in a billion. But Chris Webster says when they repeated the measurement in November of 2013, they found almost 10 times that amount.
[Chris Webster:] It was an oh-my-gosh moment.
[Joe Palca, Byline:] Webster is a scientist at NASA's Jet Propulsion Laboratory in Pasadena. Speaking today at a news conference at the annual meeting of the American Geophysical Union, Webster said they repeated the measurement four times to be sure it wasn't a fluke. It wasn't. But when they ran the measurement again two months later, the levels had gone down to what they were to start with. Webster says they don't know where the methane is coming from. It could be leaking from beneath the surface or forming through some complex chemical reaction with the Martian rocks. But there's also a chance that it was formed by something alive or something that was once alive long, long ago. Webster says they've now seen two spikes of methane in the two years the rover's been on Mars. But on the question of whether they'd see another...
[Chris Webster:] We have no idea what lies ahead in terms of the observations.
[Joe Palca, Byline:] Scientists also announced at today's news conference that they've seen preliminary evidence of complex organic molecules, specifically chlorobenzene. Once again, finding complex organic molecules does not prove that there is now or ever was life on Mars. But not finding them at all would be discouraging for those who think that Mars was once a place that could have harbored life. Joe Palca, NPR News.