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."

Comments

Viking Landers

[jd]

It has been known for some considerable time, as a result of experiments by the Viking Landers, that the soil had some interesting chemical properties. It is hardly news. However, methane from the rocks and clay cannot be the source, as the methane has been seen concentrated in small regions, whereas the rocks and soil are fairly uniform across the planet.

Re:Serpentinization: hint of water

[Sloth503]

I don't buy it. 1) yeah there was water there at one point in history but it's not around much anyomre in liquid form. 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. 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.

Yeah, it COULD happen, but not today, not on a planet so small and so old.

No life claim in original paper

[Greg Hullender]

All that's new here is the specific mechanism using Olivine. The original paper considered both biologic and non-biologic processes.

Here's the abstract of the original paper. I can't give a link because it requires a subscription to Science, but I think this is enough.

Detection of Methane in the Atmosphere of Mars
Vittorio Formisano,Sushil Atreya, Thérèse Encrenaz, Science, Vol 306, Issue 5702, 1758-1761, 3 December 2004

We report a detection of methane in the martian atmosphere by the Planetary Fourier Spectrometer onboard the Mars Express spacecraft. The global average methane mixing ratio is found to be 10 ± 5 parts per billion by volume (ppbv). However, the mixing ratio varies between 0 and 30 ppbv over the planet. The source of methane could be either biogenic or nonbiogenic,including past or present subsurface microorganisms, hydrothermal activity, or cometary impacts.

Later in the article, they expand on what they mean by "hydrothermal activity."

On the other hand, methane could have been formed by magmatic processes or stored in methane hydrates for later release to the atmosphere. Terrestrial volcanoes are not a big source of methane, and large-scale volcanism has not taken place on Mars for over 100 million years. However, small-scale outgassing of methane cannot be ruled out. A potentially larger source of methane than volcanism may come from the alteration of basalt at a temperature <150C, a process that also results in the wet-phase conversion of original CO2 into CH4 in a subpermafrost aquifer. In their chemical equilibrium computer model, Wallendahl et al. calculate that as much as 0.2 bar, ~1015 tons, of CH4 could have been produced if the only source of C in this region was the CO2 initially present in the crustal pores. Methane could have been sequestered in stable methane hydrate and gradually risen to the planet's surface. The rate of release to the atmosphere is unknown, but if one assumes that leaking has been taking place at a uniform rate over time, it would amount to ~200,000 tons year-1, which is much greater than the 100 tons or so per year needed to maintain a steady-state mixing ratio of 10 ppbv of CH4 on Mars today. Even if methane from the hydrate is being released at a rate that is a factor of 1000 slower, it would still be sufficient to account for the observations. Finally, recent laboratory experiments confirm abiogenic generation of methane in mineral-catalyzed hydrothermal reactions of CO2 and H2O at 390C and 400 bars, conditions that are likely to be encountered in subpermafrost aquifers or deep under the polar ice on Mars. Moreover, the catalyst used in the experiment--Fe-Cr oxide--is also believed to be present in the martian rocks.

Note that Olivine is Magnesium Iron Silicate (http://mineral.galleries.com/minerals/silicate/ol ivine/olivine.htm), so that's not the same as the Fe-Cr considered here, but it's not all that far a stretch either.

--Greg

Mars - The Christmas Planet

[Jah-Wren Ryel]

Olivine is green. See this picture of an isolated, but still somewhat famous, green-sand beach in Hawaii
It is green because of all the olivine in the sand, been there myself a few times:

http://www.letsgo-hawaii.com/beaches/GreenSand2_be ach.jpg
http://artemis.austincollege.edu/acad/bio/sgoldsmi th/hawaii02_images2/greensandbeach.jpg

If there really is that much olivine on the planet, we are going to have change the nickname from "the red planet" to "the christmas planet."

Olivine may be biological

[Anonymous Coward]

There is a hypothesis doing the rounds that nanobacterial metabolism is responsible for depositing mineral plaques from solution.

http://www.google.com.au/search?hl=en&q=nanobacter ia+olivine&btnG=Search&meta=

Notably, the microfossils found in the martian meteorite are thought to be of nanobacterial origin.

Some chemist please...

[Vo0k]

What process does produce the methane then?
Olivine+Water -> Serpentine+Methane+?

So:
x*(Mg2SiO4) + y*(Fe2SiO4) + z*(H2O) -> a*(several longish formulas for different kinds of Serpentine) + CH4 + ?

So where's the carbon coming from? I don't see any on the left side? All nice and pretty but carbon isn't all that common outside Earth, and is fundamental for building proteins - that is earth-like life, and there's no methane without carbon.

Re:Serpentinization: hint of water

[Rei]

Mars is likely not frozen solid. Just because we don't see eruptions going on nonstop on a major scale doesn't mean that they don't occur in recent geologic history. If some alien started observing Earth a couple decades ago using that same logic, they would conclude that megatsunamis and supervolcanoes don't occur on Earth, that the Sahara has always been a desert, and that we've always had high carbon-13 concentrations in our atmosphere.