ON THE ESCAPE OF OXYGEN AND HYDROGEN FROM MARS

被引:57
作者
FOX, JL
机构
[1] Institute for Terrestrial and Planetary Atmospheres, State University of New York, Stony Brook
关键词
D O I
10.1029/93GL01118
中图分类号
P [天文学、地球科学];
学科分类号
07 ;
摘要
Escape rates of oxygen atoms from dissociative recombination of O2+ above the Martian exobase are computed in light of new information from ab initio calculations of the dissociative recombination process, and our recently revised understanding of the Martian dayside ionosphere. Only about 60% of the dissociative recombinations occur in channels in which the O atoms are released with energies in excess of the escape velocity. Futhermore, we find that the computed escape fluxes for O depend greatly on the nature of the ion loss process that has been found necessary to reproduce the topside ion density profiles measured by Viking. If it is assumed that the ions are not lost from the gravitational field of the planet, as required by an analysis of nitrogen escape, the computed average O escape rate is 3 x 10(6) cm-2 s-1, much less than half the H escape rates inferred from measurements of the Lyman alpha dayglow, which are in the range (1 - 2) x 10(8) cm-2 s-1. Suggestions for restoring the relative escape rates of H and O to the stoichiometric ratio of water are explored. The final resolution of this problem may have to await a future aeronomy mission to Mars.
引用
收藏
页码:1747 / 1750
页数:4
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