Update on Mars' atmosphere, Media briefing on NASA Jan 15th Options

[Stu]

Interesting...

http://www.spaceref.com/news/viewpr.html?pid=27336

[silylene]

i do wish that the researchers did not seriously consider photochemical generation of methane as a significant source of abiogenic methane.

Please refer to this thread, or even older threads in SDC (with many references) : http://www.unmannedspaceflight.com/index.p...&hl=methane

From the synopsis of the press conference I read on SDC by MW (sorry, I missed the press conference): I would like to see chemcial kinetic rate data that photolysis takes 'centuries', or was this a conjecture? It would need to be a steady state effect: methane is both being produced and being lost. The concentration observed reflects the chemical kinetics of these two processes.

The map of methane production shown (I recall we went over this before, in the pre-Pluck and also pre-crash SDC forums), and indeed in the pre-crash SDC also!) gives the highest methane production in the Martian equitorial band. This is exactly what would be expected if it were a photochemical process, since this would occure in the areas of highest irradiance.

The photochemical process I proposed (see the link above, or for more information, the older links in SDC) was a photoreduction of CO2 catalyzed on metal oxide dust surfaces with hydrogen (which comes from water). The dusts (TiO2, for example, this works with several types of oxides) serve as catalysts for this effect. in fact, I would expect areas in which the dust is uplifted due to winds or dust devils to expose more dust catalyst for methane photoproduction. So you may see the highest rates where there is both high irradiance, and higher concentrations of exposed metal oxide dusts. I also recall about 2 yrs ago that, I came across a paper which found some atmospheric photoreduction chemistry occuring on the dusts from the soil surfaces in Chile'se Atacambra desert, which is a rather good stand-in for the Martian conditions.

Also, one would need to correlate the seasonal variation lifting or exposure of exposure of dusts which may serve as catalysts. And/or correlate the seasonal variation in the concentration of H2O in the atmosphere may be inportant too, as this is the source of H2 for the photreduction of CO2 to methane.

Until I see more, I am very unconvinced of the need for a biogenic methane source. I am looking forward to reading their journal paper to see how they treated the photochcemical generation.