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Methane on Mars varies with the seasons

Posted by Emily Lakdawalla

15-01-2009 15:53 CST

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A highly unusual press announcement went out on Monday, stating "NASA will hold a science update at 2 p.m. EST, Thursday, Jan. 15, to discuss analysis of the Martian atmosphere that raises the possibility of life or geologic activity." Talk about poking the beehive. The listed participants on the briefing were the chief Mars science officer at NASA (Michael Meyer), two Mars atmospheric scientists I already knew of for their research into methane on Mars (Michael Mumma and Sushil Atreya) and two other scientists I hadn't seen before (Geronimo Villanueva and Lisa Pratt). The placeholder title page on NASA TV stated: "MARS: AN ACTIVE PLANET."

There'll be more information on the press briefing in a news story on this site later today or tomorrow -- Amir Alexander is tracking down the original paper (published in Science Express, where the journal Science publishes advance versions of especially exciting research results before they get formally published in the journal) and is writing a formal story. In the meantime, here's my brief impressions of the press briefing.

  • Basically, the briefing is an update on the ongoing work to study the distribution and variability of methane in Mars' atmosphere by Michael Mumma and coworkers, based upon Earth-based spectroscopic studies. Mumma's work has been reported on extensively on this website by A. J. S. Rayl in the past, and I've written about it in the blog. Previous stories on the topic:
  • The new result is a set of maps of the distribution of methane on Mars that look at how the distribution changes with time. They didn't have such maps in the past, only whole-disk stuff. They found variability (which was known before); they found the variability to be seasonal; and they also found that there was more methane coming out of certain regions, particularly places like Nili Fossae, where there is orbital evidence for the presence of hydrated minerals.
  • The punch line is that the spatial and temporal variations in methane suggest some active process on Mars, which, the panel was saying, could be either geologic or biologic in origin. There's no way at present of knowing which one. Either way, it's evidence for current activity, which is pretty interesting, and which needs to be taken into account for future Mars exploration.
  • What is really needed to follow up on this study is something in orbit that's capable of mapping across both space and time the trace gases in Mars' atmosphere. And not just methane; they need to be able to look for other gases in association with methane that could help pin down whether the methane has a geologic or biologic origin, or some combination.
Here's some quotes from the briefing...

Michael Meyer: "What we have here is not evidence for life, but it's evidence for active processes. We know that it's in the atmosphere, and we know that it varies with time. And that variability is what leads us to conclude that something must be happening on a very active Mars. What we don't know is whether these plumes of methane are of biological or geological origin."

Sushil Atreya: "The take-home message is that whether it's biology or its geology, [Mumma's] observations seem to indicate that there are localized aquifers on Mars, and their short lifetime indicates the presence of powerful oxidants on Mars."

Lisa Pratt: "Given the lack of really compelling evidence for deep, active fracturing and faulting to keep water-rock reactions going, it's time, it's prudent, that we begin to explore Mars looking for the possibility of a life form that's exhaling methane."

Michael Mumma: "We do not see certain gases that would be expected if the methane were produced by volcanoes, particularly sulfur dioxide. It's been searched for. It is not present at the expected level if Mars ever evolved volcanism that produced [sulfur dioxide] at the same abundance as one sees, relative to methane, in terrestrial volcanoes. So that part of the evidence does not support volcanism."

A couple of other random notes: although Mars Express is capable of detecting methane in Mars' atmosphere, it is unable to observe temporal variability because its sensitivity is low enough that its measurements need to be averaged over too much time.

Good question from the press: Nili Fossae was recently eliminated from consideration as a possible landing site for Mars Science Laboratory; does this make it look more interesting? Meyer: Nili Fossae was eliminated because it was at the limits of MSL's EDL capabilities...you're right, we now have two more years to consider, Nili Fossae is not ruled out.

Good question from the press: For a future sample return mission, how far down would it have to drill to reach where this methane may be stored or generated? Pratt: You'd have to get down at least several meters, below oxidants, so a shallow drill won't do it.

 
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