Mars Methane Pairs with Water?

Mars Odyssey has found what appears to be subsurface ice near where new methane concentrations may also appear when measured by Mars Express.
Image Credit: NASA

Recent analyses of ESA’s Mars Express data reveal that concentrations of water vapor and methane in the atmosphere of Mars significantly overlap. This result, from data obtained by the Planetary Fourier Spectrometer (PFS), gives a boost to understanding of geological and atmospheric processes on Mars, and provides important new hints to evaluate the hypothesis of present life on the Red Planet.

PFS observed that, at 10-15 kilometers above the surface, water vapour is well mixed and uniform in the atmosphere. However, it found that, close to the surface, water vapor is more concentrated in three broad equatorial regions: Arabia Terra, Elysium Planum and Arcadia-Memnonia.

Here, the concentration is two to three times higher than in other regions observed. These areas of water vapor concentration also correspond to the areas where NASA’s Odyssey spacecraft has observed a water ice layer a few tens of centimeters below the surface, as Dr Vittorio Formisano, PFS principal investigator, reports.

New in-depth analysis of PFS data also confirms that methane is not uniform in the atmosphere, but concentrated in some areas. The PFS team observed that the areas of highest concentration of methane overlap with the areas where water vapor and underground water ice are also concentrated. This spatial correlation between water vapor and methane seems to point to a common underground source.

The Planetary Fourier Spectrometer (PFS).
Image Credit: ESA

Initial speculation has taken the underground ice layer into account. This could be explained by the ‘ice table’ concept, in which geothermal heat from below the surface makes water and other material move towards the surface. It would then freeze before getting there, due to the very low surface temperature (many tens of degrees Celsius below zero).

Further investigations are needed to fully understand the correlation between the ice table and the presence and distribution of water vapour and methane in the atmosphere.

In other words, can the geothermal processes which ‘feed’ the ice table also bring water vapor and other gases, like methane, to the surface? Can there be liquid water below the ice table? Can forms of bacterial life exist in the water below the ice table, producing methane and other gases and releasing them to the surface and then to the atmosphere?

The PFS instrument has also detected traces of other gases in the Martian atmosphere. A report on these is currently under peer review. Further studies will address whether these gases can be linked to water and methane and help answer the unresolved questions Methane is onsidered suggestive of life, but it also can be made by biological or non-biological processes.

Mars as seen near opposition late August 2003, by the Hubble Space Telescope. Click image for larger view. Arabia Terra is one region thought to have concentrated methane and water vapor close to the surface.
Credit: NASA/STSci/Hubble; Captioning credit MSSS/ ASU Themis/ NASA/ JPL

During a recent astrobiology conference debate on terraforming, planetary scientist David Grinspoon of the Southwest Research Institute discussed what methane findings might broadly mean: "But in my view, I think we’re going to find that Mars does not have life. We may have fossils there. I think it’s the best place in the solar system to find fossils. Of course, I could be wrong about this and I’d love to be wrong about it, and that’s why we need to explore. If the methane observation is borne out, it would be, to me, the first sign that I really have to rethink this, that maybe there is something living there under the ice."

At the same meeting, NASA’s Planetary Protection Officer, John Rummel, described the alternative explanations: "methane in the atmosphere…is a detection from the planetary Fourier spectrometer. ESA, the European Space Agency, has put out an announcement that it’s been detected at 10 to 20 parts per billion. Well, methane in the atmosphere on Mars can mean one of three things: either vulcanism, possibly microbial life, or maybe cows. We haven’t seen the cows yet. I doubt that we’ll find them. But one of the other two would be a very interesting thing to find out."

In-situ observations by future lander missions to Mars may provide a more exhaustive solution to the puzzle. Rummel concluded: "Whether or not we can find more methane on one part of Mars than another is going to take either more measurements from abroad or an instrument in-situ, perhaps in orbit around Mars, that can really make high-definition measurements. So these are things for people to propose for future Scout opportunities or future Discovery opportunities to really nail it down. Then we’ll have to go to those places and find out what’s going on there."

Related Web Pages

Great Terraforming Debate: Part I
Great Terraforming Debate: Part II
Great Terraforming Debate: Part III
Great Terraforming Debate: Part IV
Great Terraforming Debate: Part V
Great Terraforming Debate: Part VI
Great Terraforming Debate: Part VII
Mars Exploration Rover Mission: Home
NASA Mars Exploration Program