HR: 14:30h
AN: P23A-05    [Abstracts]
TI: A Sensitive Search for SO₂ in the Martian Atmosphere: Implications for Seepage and Origin of Methane
AU: * Krasnopolsky, V A
EM: vkrasn@verizon.net
AF: Department of Physics, Catholic University of America, 620 Michigan Avenue, N.E., Washington, DC 20064 United States
AU: Greathouse, T K
EM: greathouse@lpl.usra.edu
AF: Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, TX 77058 United States
AU: Richter, M J
EM: richter@physics.ucdavis.edu
AF: Physics Department, Uviresity of California, One Shields Avenue, Davis, CA 95616 United States
AU: Lacy, J H
EM: lacy@astro.as.utexas.edu
AF: Department of Astronomy, University of Texas, RLM 15.308, Austin, TX 78712 United States
AB: We observed Mars near the peak of the strongest SO₂ band at 1364-1373 cm^-1 with resolving power of 7×10⁴ using the Texas Echelon Cross Echelle Spectrograph on the NASA Infrared Telescope Facility. The spectrum shows absorption lines of three CO₂ isotopomers and three H₂O isotopomers. The water vapor abundance derived from the HDO lines assuming D/H = 5.5 times the terrestrial value is 13±1.0 pr. μm, in agreement with the simultaneous MGS/TES observations of 14 pr. μm at the latitudes (50°S to 10°N) of our observation. Summing of spectral intervals at the expected positions of eleven SO₂ lines puts a 2σ upper limit on SO₂ of 0.8 ppb. SO₂ may be emitted into the martian atmosphere by seepage and is removed by three-body reactions with OH and O. The SO₂ lifetime, 2 years, is longer than the global mixing time 0.5 year, so SO₂ should be rather uniformly distributed across Mars. Seepage of SO₂ is less than 14,000 tons per year on Mars which is smaller than the volcanic production of SO₂ on the Earth by a factor of 700. CH₄/SO₂ is typically 10^-4 - 10^-3 in volcanic gases on the Earth, and this does not support seepage as a possible source of the recently discovered methane on Mars and makes even more plausible its biogenic origin. Possible productions of ethane and propane are weaker than that of methane, and these gases should be additionally depleted photochemically by factors of 25 and 250 relative to methane on Mars.
DE: 5405 Atmospheres--composition and chemistry
DE: 5415 Erosion and weathering
DE: 5480 Volcanism (8450)
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2005 Joint Assembly