Mars methane: from microbes or minerals?

Mars looks like it's reading from a Monty Python script: "Oi'm not dead yet; Oi'm getting bettah."

Planetary scientists announced on Thursday that they've found three regions on the red planet that have pumped methane into the Martian atmosphere.

The big question now: What's generating the gas? On Earth, it can come from geological processes. But it also comes from microbes. So, Mars could be biologically alive, geologically alive, or some combination.

The research team, led by Michael Mumma at NASA's Goddard Space Flight Center in Greenbelt, Md., gives a hint of what it thinks the source could be. But, hey, why open that envelope just yet?

Astrobiologists are tickled by the news -- even though they readily agree that the processes generating the gas are still unknown.

"The implications are quite exciting if it's not a strictly a geochemical process," says Frank Timmes, a professor at Arizona State University's School of Earth and Space Exploration in Tempe.

The first inklings of methane at Mars came via Europe's Mars Express Orbiter. In December 2004, members of the Mars Express science team reported that they had detected methane in the atmosphere. And the results showed that the methane was not evenly distributed. Some regions displayed higher concentrations than others.

Related studies with Mars Express indicated that some areas with high concentrations of methane overlapped areas of unusually high concentrations of water vapor. Since water is a necessary ingredient for organic life, the overlap presented yet another piece of an intriguing puzzle.

Many scientists were intrigued, but remained unconvinced because the Mars Express team was pressing the orbiter's instruments to the limits to get the data.

These latest results came via telescopes on Hawaii's Mauna Kea. The team used them to search for methane's chemical "fingerprints" in spectra of the Martian atmosphere. And the scientists kept at the effort for three Mars years, or seven Earth years.

In 2003, Mumma's group uncovered emissions from three areas in the northern hemisphere releasing the gas. One of the three, known as ArabiaTerra, also showed up in the Mars Express results.

The methane emissions have shown seasonal swings in concentration. Emissions have been heaviest in the northern hemisphere's spring and summer. The pace of release during these peaks -- slightly more than a pound of gas per second -- is comparable to methane seeps on a well-known patch of sea bottom off the California coast near Santa Barbara.

Oh, yes, the envelope please. In the formal research paper reporting the results via Sciencexpress, an on-line adjunct to the journal Science, the team suggests that low-temperature mineral-forming processes may be the culprit at two sites: Syrtis Major and Nili Fossae. As for ArabiaTerra? They leave that one untouched, for now.

Whatever the cause, don't be surprised if one or all of these move toward the head of the list for the US's next Mars mission, the Mars Science Laboratory rover. It's currently scheduled for launch in the fall of 2011.