[Previous] | [Session 14] | [Next]
M. J. Mumma (NASA's GSFC), R. E. Novak (Iona College), M. A. DiSanti (NASA's GSFC), B. P. Bonev (Univ. Toledo/NASA's GSFC)
CH4 and its oxidation products (H2CO, CH3OH, C2H6) on Mars have received both observational (1) and theoretical attention (2, 3), but have not been firmly detected. Owing to its short photochemical lifetime (~ 300 years), the existence of significant methane would indicate \underline{recent} release from sub-surface reservoirs; a quantitative measure of the release rate could be inferred from its present atmospheric abundance. Sub-surface methane could be primordial (reduced cosmogonic carbon) (1) or biotic in origin (4); local enhancements are expected if methane is released from discrete regions. The presence of sub-surface hydrogen concentrations on Mars has been inferred from local-enhancements in epithermal neutron fluxes measured on Mars Odyssey (5), however, independent evidence is required to establish its likely chemical form (e.g., water vs. hydrocarbons) in low-latitude sites (Amazonia Planitia, and Schiaparelli-Cassini). We suggest that enhanced methane there could test whether sub-surface hydrogen is chemically bound in hydrocarbon moieties. In any case, a quantitative measure of methane production would provide a key for assessing models of biogenic vs. primordial origins.
We conducted a deep search for methane on Mars using state-of-the-art infrared spectrometers. The R0 and R1 lines in the \nu3 vibrational band near 3.3 \mum were searched using CSHELL at the NASA IRTF (Jan. and March 2003), and Phoenix at Gemini South (May 2003). Details will be presented along with preliminary results.
This work was supported by NASA RTOP 344-32-30-10 to MJM, and NSF RUI Grant AST-0205397to REN.
1. Krasnopolsky, V.A., G.L. Bjoraker, M.J. Mumma, and D.E. Jennings 1997. JGR 102(E3):6525.
2. Wong, Ah-Son, S.K. Atreya, and T. Encrenaz 2003. JGR(Planets) 108(E4):7-1.
3. Summers, M.E., B.J. Lieb, E. Chapman, and Y. Yung 2002. GRL 29(24):2171.
4. Pellenbarg, R.E., Max, M.D., and Clifford, S.M. 2003. JGR(Planets) 108(E4):GDS 23-1.
5. Boynton, W.V., W.C. Feldman, et al. 2002. Science 297:81.
[Previous] | [Session 14] | [Next]
Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.