Solar wind sputtering effects in the atmospheres of Mars and Venus.
The consequences of the direct collisional interaction of an energetic particle flux with the neutral components of a planetary atmosphere were investigated. A combination of Monte Carlo simulations and analytical analysis suggests that solar wind sputtering could provide an important exospheric mass sink on both Mars and Venus under appropriate conditions. Sputtering of the venusian atmosphere may result in loss of He at the rate of approx 105 atoms/cm2-sec, and sputtering of the martian atmosphere could remove C, N, and O at the rates of 1 X 106 C atoms/cm2-sec, 5 X 105 N atoms/cm2-sec, and 3 X 106 O atoms/cm2-sec. Calculations based on a model martian atmosphere suggest that 99% of the N2 and 43% of the CO2 originally present could have been sputtered away over 4.5 X 109 yr. -P.Br.