The Ischia news (which Alex Blackwell has been most kindly feeding into the comments threads) is definitely interesting stuff. At the Mars meeting on Ischia Vittorio Formisano has reported that methane and water vapour are concentrated over the same three parts of Mars -- Arabia, Elysium and Arcadia. The suggestion is obviously that in each place they have a common source. One possibility, presumably, might be igneous activity that both melts ice and releases methane. Another, as Mike Mumma points out on BBC Online, is that the source could be the breakdown of clathrates -- ice with methane already trapped within it.
If you buy into the clathrates, that still leaves the question of where the methane came from open. But here’s a possibility. Imagine that under these regions there are deep aquifers with liquid water, of the sort that Steve Clifford and Tim Parker have written about. Maybe they’re the last remnants of a planet-spanning aquifer. And imagine that in these aquifers there are some jolly little methanogens. This means that in the pore spaces above the aquifers there will be both water vapour and methane. The vapour and the methane will rise up until they reach the cold rocks of the shallow subsurface, at which point they freeze, together, into clathrates. Now imagine that this is happening a little while back, in one of the ice ages when the planet’s obliquity was higher and its lower latitudes colder. Back then, clathrates just below the surface might well have been stable; today, with the lower obliquity and the warmer low latitudes, they might be breaking down.
It’s just a scenario. I’ve no idea if it’s feasible (I don’t know if you can make clathrates out of water vapour and methane in this way: on the earth you start with liquid water). And you can imagine something pretty similar going on with an abiogenic methane source. But it’s kind of fun.
Five thoughts. One is that we have to remind ourselves that this data still hasn’t been published, hasn’t been peer reviewed and hasn’t been made available to the scrutiny of other workers in the field. Doesn’t mean it’s wrong, but it’s worth bearing in mind. (Given that they were writing this up in April, there’s definitely been time for it to be submitted). Leonard David quotes Jim Garvin, NASA’s head of Mars science, saying that widespread inspection of the data will be “the real test”.
Two is that there’s no mention in the reports that I’ve seen of the purported temporal changes in methane concentration mentioned back in Nice. That said, the chart on the ESA page shows a level of 35 parts per billion, which is high. Maybe the temporal differences were actually spatial differences.
Four is that all this makes it more important than ever that the Marsis antenna gets deployed. Seeing what the subsurface looks like in these three areas has suddenly become on of the highest priorities.
Five is that I think I’m going to go and get a plane ticket to Naples and hear some more.