Slashdot Mirror
Martian Methane May Come From Rocks
An anonymous reader writes "When methane was found in the Martian atmosphere last year, some scientists thought this was indirect evidence of methane-producing bacteria. But minerals such as olivine can create methane in a process known as serpentinization. Geologists calculated that a global, 50-centimetre-thick layer of olivine could account for the methane. One geologist said, 'I'd love to see bugs, but you can't just go on hope. You have to consider the geological options.' Other scientists are unsure whether methane on Mars even exists."
I don't buy it.
I do.
Serpentinization is a low-temperature, low-pressure process where ultramafic minerals (like olivine) are introduced to water. They metamorphose into serpentine-group minerals. It is a common surface to near-surface process on Earth. (It is the opposite of most other metamorphic reactions, where an increase of pressure/temperature causes the change... in this case, it is the decrease.)
1) yeah there was water there at one point in history but it's not around much anyomre in liquid form.
Yes, but we don't know what is below the surface. It is likely that mars is still fairly warm in the middle due to remnant heat and radioactive decay.
2) Mars is tiny, less than 20% the size of the earth, while there was at one time tectonic activity which could have provided the necessary heat / pressure to do this, the planet is currently frozen solid and has been for some time. It just doesn't have the mass (like earth does...) to keep tectonic activity going on.
Io, moon of Jupiter, is smaller than Mars and has ongoing tectonic activity. It has nothing to do with the mass of a body, it has everything to do with heat, which Mars has little of, for sure, but once had plenty of... look at Olympus Mons.
There is no evidence that Mars is "frozen solid". It could still have a soft core. In any case, it is likely to be rather warm in the middle, still.
3) without a constant (and modern) method for creating this methane, it all would have blown away like the rest of the Martian atmosphere, the planet is cold, nothing geologic is going on there anymore.
I agree with the geologists. The explanation is rather simple: There isn't a whole lot of water on Mars, so water contact with olivine is scarce. Thus, the reaction is very slow. If there were sh*tloads of olivine in the subsurface Mars, and there may be, then serpentinization could go on for a long time.
Why do I think there's a lot of olivine in Mars? Because there is a lot of olivine in the Earth. The bulk of the mantle is peridotite, an olivine-pyroxene rock.
But wait, there's more! There might be a large amount of olivine on the surface of mars. Olivine is a quite common mineral to find in basalt flows on Earth, existing as phenocrysts or mantle xenoliths. Matter of fact, I was looking at some olivine crystals in some basalt in central Oregon yesterday.
Now, bedrock exposures at the surface of Mars have been observed to be largely a basalt-like rock. In fact, it appears to be the main rock type on most of the surface of mars.
(Interestingly enough, basalt also happens to be the most common crustal surface rock type on Earth, given that it is the surface rock of oceanic crust.)
It may be that there is a large amount of olivine on Mars, and a limited supply of water would cause the reaction to be slow and sustained. It could go on for a long time.
I'm not saying life does not exist, in fact I defended the idea in my Slashdot journal a year or so ago, but I wouldn't pin all the methane production on life when another simple explanation exists.
"Alcohol, Tobacco, Firearms, and Explosives" should be a convenience store, not a government agency.
Olivine is olive-green.
(I knew that geology elective would come in handy someday.)
"This is totally insecure, but very convenient."
HTH.
Mike.