WC Archive

In March, scientists on the Mars Express mission reported finding small concentrations of methane in the Martian atmosphere. The discovery has been tentatively confirmed by Earth-bound observers using spectrographic equipment (although their findings have not yet been published in peer-reviewed journals). Methane in the atmosphere is odd, however, for a number of reasons. Ultraviolet light destroys atmospheric methane fairly quickly, in planetary terms -- on the order of a few centuries. That means that the methane couldn't have been a leftover from Mars' past. In addition, methane is produced on Earth from one of two sources: geological activity and biological activity. But there's little evidence of active geology on Mars: the volcanos appear dead, and surface lava is millions of years old. Still, low levels of geological activity can't be completely ruled out.

Now comes word that the Mars Express team has mapped the Martian methane concentrations and discovered that they align startlingly well with measurements (by NASA's Odyssey orbiter) of what appears to be water-ice just under areas of the Martian surface.

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National Geographic and New Scientist have more details. With the possible water-methane correlation, the idea that Martian atmospheric methane has a biological origin takes on greater weight, as water would be required for microbial methane production, but not (necessarily) for geological production. In addition, the Mars Express team has very cautiously noted that they may have also identified atmospheric hydrogen sulfide and formaldehyde, which are also strongly correlated to biological activity. Those results have not yet been fully reviewed.

All of these arguments remain controversial. The Odyssey water-ice findings are based on second-hand evidence, and the methane findings haven't yet been confirmed by broadly-accepted research. It is quite possible that all of these readings are false, or have an explanation far more prosaic than continued geological activity or Martian life.

Mars researchers will evaluate any and all possible alternative explanations before accepting any of this as signs of extant Martian life. That's not out of stubbornness or a refusal to accept the possibility; it's simple due diligence. For something this big -- the discovery of life off of Earth -- they need to be certain, absolutely certain. There's a good chance that, even if life is there, scientists will come up with a well-grounded non-biological explanation for the results, and the question of Martian microbes will remain open. In that case, we keep searching.