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R.E. Novak (Iona College), M.J. Mumma (NASA's Goddard Space Flight Center), S. Lee, L. Ivanov (Iona College), B. Bonev (University of Toledo - NASA's GSFC), G. Villanueva (NASA's GSFC)
Observations of the Martian atmosphere were taken on June 2 and 3, 2005 (Ls ~ 223, del dot = -10.9 km/sec) at NASA-IRTF using CSHELL. Column densities of HDO and H2O were extracted from individual spectral lines near 3.67 and 3.29 microns. From these, a latitudinal map of D/H was constructed at 0.6 arc-second intervals along the entrance slit (N-S on Mars). A 2-D map of ozone in the middle atmosphere was constructed by stepping the slit E-W at 1.0 arc-second intervals across Mars and measuring O2(singlet Delta) emissions near 1.27 microns . Ozone is photolyzed by UV sunlight (Hartley bands) producing O2(singlet Delta); emissions from this state are used as a tracer for atmospheric ozone above 20 km; the state is quenched by carbon dioxide at lower altitudes. These results will be compared to results taken at other seasons (Ls ~ 67 in 1997, Ls ~ 155 in 2003, and Ls ~ 333 in 2004). The D/H and ozone column densities have been found to vary with both latitude and season. The higher global D/H value on Mars compared to the Earth is attributed to differential Jeans escape of D and H over geologic time. The observed differences with latitude and season could be the signature of Rayleigh distillation, a process in which the different mean temperatures of the polar caps cause a different degree of HDO sequestration. The observed latitudinal and seasonal variations may be the signature of different amounts of enrichment in the polar caps. The seasonal variation of the observed O2(singlet Delta) emission is believed to be anti-correlated with the presence of water above 20 km which varies considerable between aphelion and perihelion. This work was partially funded by grants from NASA Planetary Astronomy Program (RTOP 344-32-51-96 to MJM) and NSF RUI Program (AST-0205397 to REN).
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.