Mars: An Evolving Atmosphere

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Science  28 Jan 1972:
Vol. 175, Issue 4020, pp. 443-445
DOI: 10.1126/science.175.4020.443


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.