Other
Scientific paper
Dec 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005agufm.p51d0967a&link_type=abstract
American Geophysical Union, Fall Meeting 2005, abstract #P51D-0967
Other
5220 Hydrothermal Systems And Weathering On Other Planets, 5405 Atmospheres (0343, 1060), 5470 Surface Materials And Properties, 6225 Mars
Scientific paper
Methane has been detected in the Martian atmosphere at a concentration of approximately 10 ppb. The lifetime of methane against decomposition by solar radiation is around 300 years, strongly suggesting that methane is currently being released to the atmosphere. By analogy to Earth, possible methane sources on Mars include active volcanism, hot springs, frozen methane clathrates, thermally matured sedimentary organic matter, and extant microbial metabolism. The discovery of any one of these sources would revolutionize our understanding of Mars. The concentration of atmospheric methane is generally constant around the planet, reflecting effective mixing of the atmosphere. However, measurable variations have been observed, suggesting localized sources of this gas. The highest values have been measured over three large areas: Arabia Terra, Elysium Planum, and Arcadia-Memnonia. We are employing the extensive geological and geophysical datasets from Viking, Mars Odyssey, and Mars Global Surveyor in a search for possible methane sources in Arabia Terra. Arabia Terra was chosen for study as it contains indicators of sedimentary processes and water that are unique and thus may indicate an unusually promising setting for the presence of biogenic methane. We have completed a preliminary survey of Arabia Terra (0 to 40 N, 20 W to 60 E) using Mars Orbiter Camera high resolution images. We documented the locations of layered deposits within craters and on intercrater plains, the locations and orientations of faults displacing layers, and the locations of craters with bright rims. Areas containing all of these features in close association may show promise as sources for the methane gas in Mars' atmosphere. A total of 1011 images were examined, and 811 showed layered outcrops. Layers were seen in every 10 x 10 degree latitude/longitude bin. Excellent examples of layered outcrops occur both within craters and on the plains. The highest concentrations of layers overlie Noachian cratered plains units, while few layers overlie Hesperian and Noachian ridged units. Layers are concentrated in the western half of the region, generally above the -2000 m contour. Faults are rare, and concentrate in the SW corner of the region, in the area from 4 to 11 N and 1 to 11 W. Craters with bright rims generally occur between 0 and 20 W. An analysis of these preliminary data suggests that the southwest quadrant of Arabia Terra, particularly in the area of 2 to 12 N, 5 to 12 W, is a prime area for more detailed exploration in the search for sources of methane.
Allen Christine
Oehler Dorothy Z.
Venechuk E. M.
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