HR: 14:25h
AN: P32B-04    [PDF]
TI: Obliquity-Driven Volatile Cycling in the Tropics and Mid-Latitudes of Mars.
AU: * Mischna, M A
EM: mischna@ucla.edu
AF: University of California, Los Angeles, Department of Earth and Space Sciences 595 Charles Young Drive East, Los Angeles, CA 90095 United States
AU: * Mischna, M A
EM: mischna@ucla.edu
AF: California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125 United States
AU: Richardson, M I
EM: mir@gps.caltech.edu
AF: California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125 United States
AU: McCleese, D J
EM: daniel.j.mccleese@jpl.nasa.gov
AF: California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125 United States
AU: Vasavada, A R
EM: ashwin@ess.ucla.edu
AF: University of California, Los Angeles, Department of Earth and Space Sciences 595 Charles Young Drive East, Los Angeles, CA 90095 United States
AU: Wilson, R J
EM: rjw@gfdl.noaa.gov
AF: Geophysical Fluid Dynamics Laboratory, PO Box 308, Princeton, NJ 08542 United States
AB: The placement of water within the martian regolith may occur through any of several means, the most important of which appear to be vapor diffusion, surface adsorption and subaerial deposition. In order to understand the relative importance of each of these modes during past periods of higher obliquity, we have linked a vapor and thermal diffusion model to the GFDL Mars GCM, and permitted water (as ice, vapor or adsorbate) to interact freely between the atmosphere and regolith. Our results strive to explain both the unique latitude-dependent terrain found in the mid-latitudes of Mars and existence of the expansive subsurface ice reservoirs discovered by Odyssey GRS data. Results from the Odyssey GRS instrument indicate ice abundances poleward of 60$^{\circ}$ (up to 90% by volume) vastly greater than one would expect based upon simple diffusion and the assumed porosity (40%) of the regolith. This disparity led to our initial investigation into subaerial deposition and subsequent sublimation as a means of inserting ice within the regolith. Our most recent work continues this investigation, and permits us to explore the importance of surface adsorption and diffusion of atmospheric vapor as well. Earlier results from the GFDL MGCM have suggested that at high obliquity, ice is not homogeneously distributed across the surface within the latitude band having the coldest annual mean temperatures. Rather, water is preferentially deposited as localized ice ``sheets'' in regions of high thermal inertia and/or high topography. Such findings neglected the thermal inertia feedback of surface ice, which will permit ice to be retained more uniformly within this latitude band. This ice/thermal inertia feedback has been included in our present work. Lastly, we have performed both 1-D and 3-D simulations of the regolith-atmosphere interaction to determine the efficacy of the deposition-sublimation, obliquity-dependent layering mechanism for a full obliquity cycle ($\sim$100,000 years).
DE: 0343 Planetary atmospheres (5405, 5407, 5409, 5704, 5705, 5707)
DE: 1620 Climate dynamics (3309)
DE: 3344 Paleoclimatology
DE: 5445 Meteorology (3346)
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2003 Fall Meeting