Mars: An Evolving Atmosphere

Abstract

Photochemical reactions in the martian exosphere produce fast atoms of oxygen, carbon, and nitrogen and provide large escape fluxes of these elements. They appear to play a crucial role in the evolution of the martian atmosphere. The relative outgassing rates of H₂O and CO₂ on Mars are comparable with terrestrial values, although absolute rates for Mars are lower by a factor of 10³. Nitrogen is a trace constituent, less than 1 percent, of the present martian atmosphere.