DPS 35th Meeting, 1-6 September 2003
Session 14. Mars Atmosphere II
Poster, Highlighted on, Wednesday, September 3, 2003, 3:00-5:30pm, Sierra Ballroom I-II

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[14.22] Time-Dependent Calculations of an Impulsive Impact-Triggered Runaway Greenhouse Atmosphere on Mars

T.L. Segura, O.B. Toon (LASP/University of Colorado), C.P. McKay (NASA-Ames Research Center)

The existence of a few dozen craters of size 200 km and greater proves that large (30-250 km diameter) impacts were abundant in the early history of Mars. Injected water from three sources (the impactor itself, water innate to the crater, and from melting of the polar caps) provide periods of rain following such impacts. Very hot (> 1600 K), global debris blankets are another consequence of these large impacts, and these layers create a thermal pulse that propagates into the subsurface, melting additional water. Both the melted and precipitated water and debris blanket combine to produce a temporarily altered climate on the planet. This research provides the first time-dependent modeled calcuations of this altered climate, and focuses in particular on a possible "runaway" greenhouse state that might be initiated as a result of the additional heat and a sufficiently rapid supply of the melted and precipitated water to the atmosphere. Our model is a 1-D radiative-convective model coupled to a 1-D model of the regolith to calculate the evolution of the surface and subsurface temperatures. The effects of latent heating, cloud condensation, precipitation, and evaporation are included in the model.

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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.