Scientists have discovered large plumes of methane gas in the Martian atmosphere, a key marker for biological processes on Earth but not convincing proof that rudimentary life forms exist on Mars.
A team of scientists led by Michael Mumma of the Goddard Space Flight Center in Maryland first detected the gas in 2003, using infrared spectrometers on three ground-based telescopes. At its peak, the plumes contained around 19,000 metric tons of methane, a large amount comparable to the seep at Coal Oil Point offshore of Santa Barbara, Calif.
The source of the methane is still a mystery, the scientists said in a briefing at NASA headquarters in Washington, D.C. But its existence proves that Mars is not the dead desert planet that many planetary scientists have believed it to be.
“Mars is active,” said Michael Meyer, head of NASA’s Mars program. “Whether it’s geology or biology, we don’t yet know.”
On Earth, the natural gas that heats our homes is mostly methane. About 90 percent of the methane gas released into our atmosphere is produced by biological processes, the largest contributors being bacteria in wetlands and the burping of cattle. The methane is released as a waste product by microbes reacting to hydrogen.
But methane is not a sure-fire indicator of life. Geological processes such as the interaction of water and molten rock in volcanoes can produce methane. On Titan, Saturn’s largest moon, liquid methane is so plentiful it flows in rivers. Titan is so cold that it is extremely unlikely that the methane is being produced by living organisms.
While cautioning that more work needs to be done, the scientists said the absence of other gases that would be expected if the source is volcanic activity is one indicator that the methane on Mars could be produced by living organisms.
“This is exciting to think about in terms of life on Mars,” said Lisa Pratt, a geologist at the University of Indiana. “Given the lack of compelling evidence of heating and faulting, it’s prudent for us to begin to explore Mars looking for life forms that are exhaling methane.”