Mars scientists in Europe and the United States have detected tantalizing signs of methane gas in the Martian atmosphere, and cannot yet explain why it’s there.
Methane is commonly exuded by living organisms and fermentation. It can also belch to the surface during volcanic eruptions, and can be carried by comets that at times have crashed into Earth and other planets.
The amounts of atmospheric methane detected by instruments aboard the European Space Agency’s Mars Express spacecraft now orbiting the planet are extremely small — barely more than 10 parts per billion, but the find is already creating a major buzz among Mars researchers.
Steven Squyres, now famed as the leader of the team guiding the Mars rovers Spirit and Opportunity on their epochal tour of the Martian surface, would not talk to a reporter about the European find this week after a talk to a major astrobiology conference at NASA’s Ames Research Center in Mountain View.
But Bernard Foing, an organic chemist on the Mars Express team who also attended the astrobiology meeting, cited three possible major sources for the methane.
First, it could be emerging from a Martian volcano that is unexpectedly erupting right now, even though little or no volcanic activity has been observed on Mars from high-resolution ground-based telescopes on Earth or from orbiters circling the Red Planet.
Second, the gas could have carried into the planet’s atmosphere by a grazing comet or asteroid, even by one that hit the surface very recently.
And third — probably the least likely but certainly the most dramatic of all — it could be emerging from beneath the Martian surface where some kind of living organisms — bacteria, perhaps — might be surviving and nourishing themselves by chewing on rocks containing chemicals that serve as a source of energy.
One thing is certain, however: Wherever the methane comes from, it must be either of relatively recent origin or be continuously replenished, because the gas lasts only a few hundred years or so before it oxidizes into water and carbon dioxide.
“We cannot know more until we find out more,” Foing said in an interview, “and that will take many more observations both to confirm that the gas is there and to locate its source on the planet.”
The European Space Agency first disclosed the methane find Monday after Vittorio Formasino, the lead scientist for the spacecraft’s Planetary Fourier Spectrometer, confirmed that the instrument had indeed detected methane’s chemical signature.
“The first thing to understand is how exactly the methane is distributed in the Martian atmosphere,” Formasino said. “Based on our experience on Earth, the methane production could be linked to volcanic or hydrothermal activity (sub-surface hot springs) on Mars.”
But Formasino added cautiously: “If we have to exclude the volcanic hypothesis, we could still consider the possibility of life.”
The first tentative detection of methane in the Martian atmosphere was announced last year by Michael Mumma, a physicist at NASA’s Goddard Space Flight Center near Washington, D.C. He found the telltale evidence in observations by ground-based telescopes at Cerro Pachon in Chile and the giant Keck II instrument on Mauna Kea in Hawaii.
Vladimir Krasnopolsky of the Catholic University of America in Washington, D.C., reported Monday that he and his colleagues had also found evidence of Martian methane using the Canada-France-Hawaii telescope atop Mauna Kea. — San Francisco Gates