Document Type

Article

Publication Date

9-1993

Abstract

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 × 106 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) × 108 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.

Comments

Copyright © 1993 by the American Geophysical Union.

The following article appeared in Geophysical Research Letters 20(17), and may be found at http://onlinelibrary.wiley.com/doi/10.1029/93GL01118/full

Permission to Deposit an Article in an Institutional Repository:

Adopted by Council 13 December 2009.

AGU allows authors to deposit their journal articles if the version is the final published citable version of record, the AGU copyright statement is clearly visible on the posting, and the posting is made 6 months after official publication by the AGU.

DOI

10.1029/93GL01118

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