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Martian Methane May Be Created By Lifeforms
Following our recent discussions about the growing evidence pointing to possible life on Mars, reader skywatcher2501 writes with news of a study that has ruled out one possible explanation for the levels of methane seen on that planet — that it might be replenished by disintegrating meteors entering the atmosphere. So two theories remain: either the gas is created as a by-product of reactions between volcanic rock and water, or it is a by-product of a lifeform's metabolism.
The problem is that on mars all methane should vanish in months due to oxidizing soil. Therefore something must be replenishing it.
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There are recent studies showing it may be possible that some of our methane on Earth is being created by the high pressure/temp conditions in the earth's mantle, rather than exclusively by the decay of organic matter. A written article on this, or an NPR segment (about 1/3 of the way into the audio file).
Titan, which is quite a bit smaller than Mars, has an atmosphere 1.5 times as dense as Earths.
Titan is also extremely cold, and has less agitation of its atmosphere; it has protection from Saturn's magnetic field (which it may be holding onto as it does pass through) and is at a much greater distance from the Sun than Ganymede is; the gases compositing the atmospheres of each are also different, which in consideration of their properties may definitely matter: my point is, that neither singly mass, nor density, nor solar distance, nor composition, nor magnetic properties, i.e. any single variable, is responsible for atmospheric density. Mars, however, is both so close to the Sun to be affected by solar winds, and so mass deficient relative to those other factors, that the planet isn't adequate for holding onto a dense atmosphere (of almost any composition): if it were around a dead star, or floating through space away from agitations, etc., then sure, you'd expect it could hold a dense--perhaps frozen (as much of Mars's atmosphere may, in fact, be, and thus on its surface and in its soil)--[r] atmosphere; but considering the variables for holding the kind of gases we'd even be interested in, it's not much worth our time, except perhaps to mine, or for other conditions for experimentation.
The same, unfortunately, applies to Venus--is inadequate to hold onto the kind of atmosphere we'd be interested in, and would even if its role were reversed with Mars (which would also mean it would be too cold). We on Earth have the sweet spot positionally, in mass, gravitationally, in density, and all the other variables you could think of. I'm happy for it too! : )
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