Other
Scientific paper
Dec 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufm.p23e..02g&link_type=abstract
American Geophysical Union, Fall Meeting 2011, abstract #P23E-02
Other
[0317] Atmospheric Composition And Structure / Chemical Kinetic And Photochemical Properties, [0328] Atmospheric Composition And Structure / Exosphere, [0343] Atmospheric Composition And Structure / Planetary Atmospheres, [6225] Planetary Sciences: Solar System Objects / Mars
Scientific paper
Accurate determination of the escape rate of various constituents from Mars is important for understanding its atmospheric evolution over time and estimating the total amount of liquid water present on Mars in earlier epochs. We report the results of a detailed theoretical analysis of a novel, collisional mechanism of escape of molecular hydrogen and its isotopologues from martian atmosphere. The escape of H2 is induced by the elastic and inelastic collisions between the hot oxygen atoms and the thermal hydrogen molecules. To accurately describe the O + H2(v,j) collision we have calculated elastic, inelastic, and reactive total and differential cross sections using advanced methods of the quantum scattering theory. The energy transfer rates were self-consistently determined for different translational, rotational and vibrational excited states of H2. The distribution of the translational energy of the recoiled H2 molecules has been modeled and non-thermal rotational and vibrational distributions of the escaping H2(v',j') molecules were constructed. To evaluate the non-thermal escape flux of H2 we used a 1D column model of martian atmosphere with realistic hot oxygen production rates and densities of atmospheric gases. We find that the non-thermal H2 escape rates, computed for different solar conditions, are comparable to Jeans escape rates, while the difference becomes more pronounced for the other isotopologues. The collisionally ejected H2 has a characteristic distribution of rovibrational states with a significant fraction of populated higher rotational states, leading to possible observational identification. The described process of molecular escape is not restricted to martian atmosphere and applicable to other molecules.
Gacesa Marko
Kharchenko Vasili
Zhang Pei-Pei
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