37th DPS Meeting, 4-9 September 2005
Session 24 Mars III
Oral, Tuesday, September 6, 2005, 2:00-3:50pm, Music Concert Hall

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[24.09] New evidence for recent climate control as the source of the equatorial water equivalent hydrogen regions on Mars.

S.M. Nelli, J.R. Murphy (NMSU), W.C. Feldman (LANL)

The origin of the longitudinally confined equatorial water equivalent hydrogen (WEH) regions on Mars is disputed. Current arguments for their existence are: 1) recent ice age, 2) near-surface water table, 3) recent sublimation of the CO2 veneer of the south residual polar cap, and 4) in equilibrium with the current atmospheric conditions on Mars. The NASA Ames GCM is used to explore current Martian climate conditions as the source for the equatorial WEH-rich regions on Mars. There is a correlation between the simulated total annual deposition (but not accumulated) pattern of water ice and the equatorial WEH-rich regions on Mars. Model results indicate that local nighttime thermodynamics and thermal inertia/topography create bulk water ice precipitation regions over Arabia and Tharsis. Nighttime air in contact with the ground cools via radiation and conduction, precipitating water ice at locations where the local near-surface atmospheric temperature falls below the dew point. The highest topographic longitudes, coincident with the lowest surface thermal inertias, beget the lowest temperatures, resulting in a longitudinal wave two pattern of water ice deposition upon Arabia and Tharsis. These current longitudinally confined “wet” conditions provide water vapor that is readily available for adsorption by hydratable minerals during the night.

Support for this project comes from NASA Planetary Atmospheres Programs (NAG5-12123) and by the DOE through Laboratory Directed Research and Development funds.

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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.