37th DPS Meeting, 4-9 September 2005
Session 27 Mars IV
Oral, Tuesday, September 6, 2005, 4:20-6:00pm, Music Concert Hall

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[27.01] Methane, organics, and related trace constituents on Mars: sources, sinks, implications

S.K. Atreya (U. Michigan)

Trace quantities of methane gas have been detected by the PFS on Mars Express (1). FTS at CFHT yields similar (10 ppbv) global abundance (2). However, CSHELL at IRTF and Gemini telescope data imply substantially greater (>250 ppbv) amounts (3), which is puzzling. PFS and the IRTF/Gemini data also indicate variable abundances over the planet. This too is puzzling, considering relatively long (300-600 year) lifetime of CH4 on Mars. It is tantalizing to surmise that widely dispersed microbial colonies (extinct or extant) may be responsible for non uniform methane. This viewpoint is further bolstered by the mineralogical evidence of past (liquid) water at MER sites, especially Meridiani Plenum (4), and non uniformly distributed subsurface ice reported from Mars Odyssey (5). Indeed chemolithotrophic microbial ecosystems is one possible scenario for the presence and behavior of martian methane, but is by no means the only one (6). In fact, methane production through serpentinization is a common occurrence on Earth, and the interior of Mars (or Titan) poses no unusual challenge (6). An effective surface sink could also be responsible for non uniform CH4. Oxidizers in the surface can scrub not only methane gas from the atmosphere, but also any organic material in the soil. Electrochemistry triggered by martian dust devils and storms is potentially a large source of an oxidant, hydrogen peroxide (7). This talk will summarize the current state and discuss missing links in above story, especially isotope data (e.g., 12C/13C), organics, oxidants, sulfur and halogen species, etc. 1. Formisano, etal, Science 306, 1758, 2004. 2. Krasnopolsky, etal, Icarus 172, 537, 2004. 3. Mumma, etal, DPS, 2004. 4. Science 306, 1697-1756, 2004. 5. Science 297, 75-85, 2002. 6. Atreya, Wong, AGU, ED13D-0745: Methane on Mars, 12/2004. Also Mars International Conference, Ischia, Italy, 09/22/2004. 7. Atreya, etal; Delory, etal, Astrobiology-submitted.

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Bulletin of the American Astronomical Society, 37 #3
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