Evolutionary Modeling of Atmospheric Abundances Due to Impacts at Venus, Earth, and Mars

Abstract:

Planetary atmospheres are subject to a host of source and loss processes which affect their bulk properties and surface habitability. Impacts by comets and asteroids are unique in that they can act as either a source or loss process depending on aspects of the impact such as impactor size, velocity, and composition, as well as impact angle and target material. Here we examine multiple pre-existing models for individual impacts (Melosh and Vickery 1989; Genda and Abe 2003; Svetsov 2000, 2007; Shuvalov 2009) and create Monte Carlo models of the effect of these impacts on atmospheric abundances over a period of heavy bombardment. We find generally good agreement between final atmospheric pressures of the various models for identical input parameters. In particular, we note that impacts act as a source of atmosphere for Mars and Earth while they lead to a net loss of atmosphere at Venus. In the future this work can be expanded to track abundances of individual atmospheric components or impact-induced chemical reactions. It may also be used in the larger framework of examining multiple source and loss processes to form a more complete model of atmospheric evolution.