A non-stoichiometric model of the composition of the atmospheres of Mercury and the Moon

The likely source fluxes, atmospheric column densities, and UV irradiances have been predicted of a number of species likely to be found in Mercury's exosphere which should be derived from the regolith or from infalling meteoritic material. The predictions for important sources were based on the current knowledge of the atmospheres of the Moon and Mercury and in particular the current understanding of the abundances of Na and K as well as the available measured upper limits for other species. In particular, the column densities and observed fluxes are predicted for Ca, Al, Fe, Mg, Si, S, and OH for both atmospheres. The strongest resonantly scattered features for most of these elements fall in the UV. With current technology even the weakest can easily be detected from orbit about either Mercury or the Moon. However, it is predicted that several important species including OH and Ca may be present in sufficient abundances to be observed from the Earth. (C) 1997 Published by Elsevier Science Ltd.