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D. L. Huestis, T. G. Slanger (SRI)
Understanding the historical evolution of the Martian climate, and especially the history of water, requires detailed knowledge of the Martian atmosphere and the coupling between the surface and the atmosphere. Of particular interest is the photodissociation of atmospheric H2O into H and OH. Escape from the atmosphere of H atoms results in a net drying of the planet. The reaction OH + CO arrow CO2 + H is a key step in the photochemical stability of the atmosphere. Unfortunately we have no observations of the altitude profiles of the key minor chemical species (H2O, H2O2, HO2, OH, H, H2, O, O2, O3, CO, and CH4) in the middle atmosphere. A result is the wide divergence between models of the Mars atmosphere.
Here we describe what can be learned from observations of the Mars nightglow, in the visible and near infrared, from either the Hubble Space Telescope or a Mars lander or orbiter. The Mars nightglow spectrum has never been recorded previously, either by planetary probes or by near-Earth telescope observations. We predict that Meinel band emissions from the OH radical will be prominent features in the Mars nightglow and that these emissions will provide essential information about the abundances of hydrogen atoms and ozone molecules in the Mars middle atmosphere, and indirectly about the fate of atmospheric water. Observations of molecular and atomic oxygen emissions will provide important constraints on models of oxygen atom profiles, about which we have little direct information.
This work was supported by the NASA OSS Planetary Astronomy program.
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Bulletin of the American Astronomical Society, 34, #3< br> © 2002. The American Astronomical Soceity.