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[33.05] Non-LTE Effects on Mars: 15\mum CO₂ Limb Temperature Retrievals by Season and Latitude

W. C. Maguire, J. C. Pearl, M. D. Smith (NASA's GSFC), B. J. Conrath (Cornell), A. A. Kutepov (NAS/NRC at GSFC and Max Planck), A. G. Feofilov (Munich), P. R. Christensen (Arizona State U.)

Latitudinal averages of MGS/TES observations for a number of Martian seasons are regularly inverted using the 15\mum CO₂ infrared band to derive both nadir and limb temperature profiles. Non-LTE (local thermodynamic equilibrium) effects in this CO₂ manifold become significant above about 95 km in Mars yet contribute to observed limb radiances at lower tangent altitudes. An inversion routine which assumes LTE and a separate non-LTE routine are used in assessing the effect of non-LTE contributions on the limb retrievals. First, temperature profiles are obtained by using the LTE routine to invert MGS/TES averages. Next, we compute corresponding synthetic spectra by submitting those profiles to our non-LTE algorithm. Finally, by inverting the synthetic spectra via that independent LTE routine, the non-LTE and resulting LTE profiles can be compared. For example, with L_s near 562^o and for latitude 35^o S, between about 65-80 km tangent-point altitudes, the two profiles progressively diverge with increasing altitude, the non-LTE profile becoming warmer finally by more than 10K. We present results for a suite of latitudes and Martian seasons. A new implementation has significantly reduced computation time for these corrections.

Funding for this research is provided by the NASA Mars Data Analysis Program. We also acknowledge support by NASA for an NAS/NRC Associateship.

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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.