HR: 17:15h
AN: P34A-04    [Abstracts]
TI: Characterizing Starting Conditions for Hydrothermal Systems Underneath Martian Craters
AU: * Pierazzo, E
EM: betty@psi.edu
AF: Planetary Science Institute, 1700 E. Ft. Lowell Rd., Suite 106, Tucson, AZ 85719 United States
AU: Artemieva, N A
EM: artemeva@psi.edu
AF: Institute for Dynamics of Geospheres, Russian Academy of Sciences, Leninsky pr., 38-6, Moscow, 117334 Russian Federation
AU: Ivanov, B A
EM: ivanov@lpl.arizona.edu
AF: Institute for Dynamics of Geospheres, Russian Academy of Sciences, Leninsky pr., 38-6, Moscow, 117334 Russian Federation
AB: Mars is the first place to look for any sign of present or past extraterrestrial life. Its surface shows many features indicative of the presence of surface and sub-surface water, while impact cratering and volcanism have provided temporary and local surface heat sources throughout Mars geologic history. In particular, impact-generated hydrothermal systems could have been some of the most favorable sites for the origin of life on Mars. We present initial results of hydrocode simulations of impacts on Mars aimed at characterizing the initial conditions required for modeling the onset and evolution of a hydrothermal system on the red planet. High-resolution 3D SOVA simulations of the early stages of impact cratering indicate that the amount of melt generated in impacts is sensitive to the impact velocity. In particular, cometary impacts produce 2 to 3 times more melting than asteroidal impacts for roughly the same final crater. The particular distribution of ice in the target (mixed cells versus layering) does not appear to significantly affect the overall shock decay. However, the description of the mixed material target, mixed cells of individual materials (basalt/ice) versus mixed material equation of state, may affect the overall results and requires a more detailed investigation, both theoretical and experimental. Modeling crater collapse is a necessary step to determine the final thermal state of the target underneath. Crater collapse simulations carried out with SALEB show that the combination of shock/plastic heating and the structural uplift of initially deeper strata create a water-bearing zone at depths where water is in the liquid stability field. In the central uplift, the high temperatures cause water to evaporate (steam-driven circulation). The simulations indicate that for a mid-sized crater (rim diameter around 30 km) the hydrothermal circulation is probably restricted to a ``column'' contained well within the final crater.
DE: 5420 Impact phenomena (includes cratering)
DE: 5460 Physical properties of materials
DE: 5470 Surface materials and properties
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2004 AGU Fall Meeting