Mars Vents Methane in What Could Be Sign of Life
Friday, January 16, 2009
Something is happening beneath the surface of Mars that causes substantial amounts of methane gas to vent regularly into the atmosphere, a discovery that NASA scientists said yesterday represents the strongest indication so far that life may exist, or once existed, on the planet.
The methane is released into the atmosphere in specific areas and at regular times, they found, in a pattern that would be consistent with the gas being a byproduct of biological activity beneath the planet's parched surface.
Principal investigator Michael Mumma, of NASA's Goddard Space Flight Center, said the detection does not mean that life definitely exists on Mars, since the gas can also be produced by subsurface geological or chemical processes.
Nevertheless, "we believe this definitely increases the prospects for finding life on Mars," said Mumma, whose findings are being published today in the journal Science. "No other discovery has done as much to increase the chances of finding life."
The scientists detected the plumes of methane during two Martian summers, when the planet's large formations of subsurface ice may melt and release the gas.
Most of the methane in Earth's atmosphere is produced by bacteria in creatures large and small. Even if turns out that the Martian methane is from non-biological processes -- a far less dramatic prospect -- that would nonetheless reshape thinking about the planet, which scientists thought to be geologically dead and chemically unlikely to produce much of the gas.
Scientists have been working to confirm the presence of methane on Mars since it was tentatively detected in 2003, first by Mumma and then by scientists working with the European Space Agency. The new report confirms that discovery, describing intense, recurring but relatively brief gas releases that are consistent with either biological or active geological origins.
The new data were gleaned by NASA's Infrared Telescope Facility atop Mauna Kea, Hawaii, and a telescope in Chile. The earlier reports of methane came from Mars Express, the European Space Agency's orbiting satellite. Scientists used instruments called spectrometers to detect the "fingerprints" of methane molecules by the way they absorb sunlight.
Mumma said the methane does not last long in the Martian atmosphere, which is made up largely of carbon dioxide that breaks down the gas much more quickly than on Earth. That means, he said, that the methane detected was almost certainly released recently from underground reservoirs, although it could have been stored there for a long time.
The plumes were detected above a handful of Martian hot spots hundreds of miles apart, including Nili Fossae, Syrtis Major and Arabia Terra. Previous research has shown that liquid water once covered some of that area and detected mineral deposits that require standing water in order to form. Images taken by a Mars orbiter in 2005 also suggest that water, or liquids of some kind, might still flow at times on the surface.
Michael Meyer, head of NASA's Mars program, said at a news conference that the report would spark intense debate and probably criticism in the field. He called the science important and sound but said it would take time to see whether it would change scientists' understanding of Mars.
The methane discovery comes as researchers on Earth are finding previously unknown colonies of "extremophiles" living far below the surface and in conditions that were long considered to be uninhabitable. One of the experts at the news conference was Lisa Pratt of Indiana University, who was part of a team that identified a microbe two miles down in a South African gold mine that lives entirely without drawing energy from sunlight, a process called photosynthesis. The microbe's energy source is the radioactive decay of nearby rocks, a process known as radiolysis.