36th DPS Meeting, 8-12 November 2004
Session 32 Asteroids
Poster II, Thursday, November 11, 2004, 4:15-7:00pm, Exhibition Hall 1A

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[32.26] Sputtering from a Regolith

T. C. Cassidy, R. E. Johnson (University of Virginia)

Sputtering from a porous regolith due to energetic-particle bombardment is simulated using a Monte Carlo model. This is done in order to apply use of laboratory data on sputtering to the production of atmospheres on otherwise airless bodies in our solar system. The results of a sputtering event are assumed to depend only upon the ion angle of incidence (with respect to the local grain normal) and intrinsic properties of the regolith grains. The fate of the sputter ejecta then is affected by the sticking probability of the sputter ejecta to neighboring grains. Total sputtering yields, sputter-product exit-angle distributions, and energy distributions are calculated for application to, for example, the sodium component of the atmospheres on a number of solar system objects.

It is found that the grain shape has little effect on regolith sputtering yield. The sputter-product exit-angle distribution is little altered by the variation of the primary sputtering parameters, with the exception of the case of nearly specular sputtering. The regolith yield is usually less than that from a flat surface made of the same material and depends on the sticking coefficient. The results are in rough agreement with an earlier analytic model, but the experimental results of Hapke and Cassidy (1978) require a strongly forward-directed sputtering process.

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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.