Mars to NASA: Forget Water, Follow the Methane

Jan. 16, 2008 -- For years, NASA has been diligently following the footsteps of water on Mars to try to figure out how the planet transformed from a warm and ocean-rich world to the cold and dry desert it is today. Now scientists have another trail to follow, one that could prove to be a more direct path to answering one of the most enduring and tantalizing questions of all time: Is Earth the only place with life?

The shift in strategy is being triggered by the realization that at least three distinct locations on Mars are venting methane on an ongoing basis.

The source could be an exhaled breath of microbial life, or a chemical reaction of water on rock. But even a geologic origin of the gas has implications for life; methane, on Earth anyway, serves as a food source for some colonies of microbes that live underground.

"Either way, I think we simply have to accept the fact that while we are currently developing a strategy to search primarily for ancient life during a wetter phase of Mars, we actually also need to think in terms of present-day Mars life still holding on somewhere in the subsurface," said Lisa Pratt, a geobiologist at Indiana University.

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The first step of a revamped Mars exploration program would be a planet-wide map of the methane releases over time, said Michael Mumma, a NASA scientist at the Goddard Space Flight Center in Greenbelt, Md., and lead author of the paper in this week's Science magazine that details the methane discoveries.

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"We need a way to identify where all the active vents are, to quantify their principal gases, to identify which might be dominated by biology and which might be dominated by geochemistry, and then ... establish which are repeated year after year," Mumma said.

"That permits you to decide that this particular site is where you really want to go," he added.

No existing spacecraft -- and none currently planned -- can produce detailed maps of Mars methane, but NASA's decision to postpone the launch of a sophisticated lander, a delay due to technical reasons, may turn out to be a fortuitous coincidence.