Is Mars methane the 'breath of life'?

BY KULVINDER SINGH CHADHA

ASTRONOMY NOW

Posted: 16 January, 2009

Localised plumes of methane detected on Mars could be coming from life forms under the planet’s surface according to NASA and academic scientists. The findings were revealed in a live webcast yesterday at 19:00 GMT. Though there could be other possible, non-biological processes responsible for the methane, it is the strongest clue to date that the red planet may not be a dead world.

The team observed the planet in infrared wavelengths using the NASA Infrared Telescope Facility and Keck Telescopes in Hawaii. The observations, taking place over several Martian seasons, revealed absorption lines in the spectrum, indicative of methane. Study team member Dr Geronimo Villanueva of the Catholic University of America says, “We observed and mapped multiple plumes of methane, one of which released about 19,000 metric tons. The plumes were emitted during the warmer seasons, spring and summer, perhaps because ice blocking cracks and fissures vaporized, allowing methane to seep into the Martian air.” Crucially, the plumes were detected over areas that show evidence of ice or flowing water in the distant past. In this particular case they were Nili Fossae, south-east Syrtis Major, and east of Arabia Terra.

Graph showing localised methane release during one Martian summer (click for larger version). Image: Trent Schindler/ NASA.

But why get excited about methane? Couldn’t it just be a mundane aspect of the Martian atmosphere? Dr Michael Mumma of the Goddard Space Flight Center says "Methane is quickly destroyed in the Martian atmosphere in a variety of ways, so our discovery of substantial plumes of methane in the northern hemisphere of Mars in 2003 indicates that some ongoing process is releasing the gas." The exciting part to this is that on Earth, the majority of methane produced comes from biological sources.

Even so, caution needs to be taken as Mars is a very different place, and other processes need to be considered. For example, one of the other ways that methane could be being produced is the oxidization of iron (and in fact this is what gives Mars its red colouring). Another mechanism involves the interaction of subsurface water, carbon dioxide, and geological heat. The most likely places where these reactions would occur are those very same spots where water may have once existed.

But even taking this into account there is reason to be optimistic about the possibility of life forms on Mars, even if none have ever been detected at the surface. On Earth, microbes thrive in all sorts of places, including several miles below the ground. If the Martian surface really is too harsh for life, there’s a fighting chance that it could still thrive below ground level.

The actual location of the plumes, as detected by ground-based, infrared spectroscopy (click for larger version). Image: Susan Tawdry/ NASA.

During the webcast the scientists discussed the possibility that the methane could have remained trapped inside clathrates (a gas or liquid physically trapped in the pores of an ice, rock or other solid) and that the source of this methane, created by a geological or biological source, could have remained trapped for billions of years until it was released. Even if a biological source went extinct in that timeframe, it would be the single most momentous discovery in science, and thus worthy of investigation. Mumma says, "Right now, we do not have enough information to tell whether biology or geology (or both) is producing the methane on Mars. But, it does tell us the planet is still alive, at least in a geological sense. It is as if Mars is challenging us, saying, 'hey, find out what this means.' "

This image shows the carbon dioxide, water and internal heat combination that may be contributing to Martian methane. Is the methane totally geological, or is there indeed a biological element? A future mission like the Mars Science Laboratory should be able to tell by the measurement of isotope ratios. Image: NASA.

But how could you tell that Martian methane was indeed biological in origin? Sending a robotic mission (let alone a manned one) to drill several miles below the surface, for example, just isn’t feasible. But maybe you wouldn’t need to do that. Chemical elements usually come in different (i.e. heavier and lighter) versions called isotopes. Any life forms would likely have different isotope ratios of carbon and hydrogen (the two constituents of methane) from other processes. Life tends to go for lighter isotopes. This is detectable, and no doubt will become a priority for missions such as NASA’s Mars Science Laboratory, now scheduled for launch in 2011. So watch this space then to know if there will be an answer to one of the most enduring scientific mysteries of our time.

The work is reported in the 16 January issue of the journal Science Express .