Curious lack of methane in Mars’ atmosphere narrows the search for life

NASA announced today that the Curiosity rover has found no methane in the Martian air it has sampled, which may limit or even rule out the possibility of life on Mars.

Curiosity's results are odd, considering that astronomers here on Earth and satellites orbiting Mars have been detecting plumes of methane in Mars' atmosphere for the past 10 years. NASA even produced a map of methane detected on the planet back in 2009, using observations with their Infrared Telescope Facility on Mauna Kea, in Hawaii.

Methane can be produced by volcanic activity or even meteorite and comet impacts, but there's one other source of methane we know of that's of particular interest — microbes. From everything we know of Mars, it hasn't had active volcanoes for a very long time, and we haven't seen any major meteorite or comet impacts that could account for the methane plumes we've been seeing. Therefore, it was thought that if we were seeing methane, it might be an indication of life.

However, Curiosity took six readings of the Martian air, from spring until late summer, and it found no methane in its samples.

"There's no known way for methane to disappear quickly from the atmosphere," said study co-author Sushil Atreya, according to a NASA statement. "Methane is persistent. It would last for hundreds of years in the Martian atmosphere. Without a way to take it out of the atmosphere quicker, our measurements indicate there cannot be much methane being put into the atmosphere by any mechanism."

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These findings don't necessarily rule out life on Mars, though.

"This important result will help direct our efforts to examine the possibility of life on Mars," said Mars Exploration Program lead scientist Michael Meyer in the NASA statement. "It reduces the probability of current methane-producing Martian microbes, but this addresses only one type of microbial metabolism. As we know, there are many types of terrestrial microbes that don't generate methane."

(Photo courtesy: Andrew Bodrov/NASA/JPL-Caltech/MSSS)

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