A gas plume on Mars could turn out to be the most important discovery of the decade, or nothing but a bad smell. NASA are taking the possibility seriously and the decision on whether to retask almost two billion dollars worth of equipment to investigate will have to be made soon.
Planetary scientists at NASA's Goddard Flight Center claim to have identified hotspots of methane gas emission, extremely localized plumes whose concentration fades quickly in time. An atmosphere-wide distribution that's stable in time would indicate a balance between geological sources and destruction by sunlight. Localized sources, however, suggest much more active sources.
What's the best source of methane most people know about? Cows. That's unlikely on Mars. But backing off a level, the important factor is LIFE. NASA team leader Michael Mumma puts forward the idea that subterranean bacteria could be producing the noxious fumes, which periodically percolate to the surface in short lived bursts. But it could also be a geological source deep below the surface. The CH4 was identified spectroscopically, analyzing the exact wavelengths of the light emitted from certain regions over time. It's exactly the same strategy the astronomers of old used, "just looking at what color things are", but since we worked out (some) quantum mechanics the same light can tell us so much more. Unfortunately, it can't make the crucial distinction between life or rock-based gas.
But if we can just get a bit closer we can find out. The carbon 'C' in CH4 could be identified by the Mars Science Laboratory, almost a ton of super-science goodness. Three times the weight (and with ten times the payload) of past rovers, the MSL can analyze the carbon. Biochemical reactions prefer the isotope C-12 (six protons, six neutrons) while geological processes are just as happy with its isotope brother, C-13 (seven neutrons). A quick test of the C12:C13 ratio will tell us whether we're dealing with venting rocks or extra-terrestrial life, right next door.
A lot will depend on Mumma's paper, currently under review for publication in Science. One of the seven sites under consideration for MSL touchdown features one of the methane hotspots 'Nili Fossae'. If he can convince NASA, the Martian Laboratory may be making one small sniff for mankind.
Methane Plumes on Mars
Image credit: JPL-Caltech/Univ. Arizona/NASA
By Luke McKinney