Is the Moon really as smooth as a billiard ball? Remarks concerning recent models of sputter‐fractionation on the lunar surface

Abstract

Two recent discussions of chemical and isotopic fractionation by solar wind sputtering (Pillinger et al., 1976; Switkowski et al., 1977) are not applicable to the moon because the authors have failed to include major effects caused by the real geometry of the lunar surface. The complex reentrant micromorphology of the lunar soil drastically affects sputter‐fractionation because most of the sputtered species do not leave the moon, but strike surfaces which are partially shielded from further sputtering. At these sites fractionation is effectively controlled by desorption and angular sputtering effects rather than by sputtering yields. The mass ratio of matter which has been sputter‐deposited to that in the sputter‐altered transition layers on individual grains exceeds 100∶1.