By Kenneth Chang
Methane gas periodically wafts into the atmosphere of Mars; that notion, once considered implausible and perplexing, is now widely accepted by planetary scientists.
Why the methane is there is still a bewildering mystery. It may even point to present-day Martian microbes living in the rocks below the surface.
In Nature Geoscience on Monday, scientists working with the European Space Agency’s Mars Express orbiter reported that in the summer of 2013, the spacecraft detected methane within Gale Crater, a 96-mile-wide depression near the Martian equator.
That is noteworthy, because NASA’s Curiosity rover has been exploring that region since 2011, and in the summer of 2013 it, too, measured a marked rise of methane in the air that lasted at least two months.
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