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[62.04] Near-Infrared Spectral Mapping of Martian Volatiles During the 1999 Opposition

D. A. Glenar, G. Bjoraker, J. C. Pearl (NASA/GSFC), D. L. Blaney (JPL)

We observed Mars at K and L-band wavelengths using the Kitt Peak cryogenic grating spectrometer (CRSP) during the April 1999 opposition (L_s=130). The observations consisted of calibrated drift-scans across the Mars disk, which were reformatted into spectral image cubes spanning 2.18-2.42 microns with spectral resolving power \lambda/\Delta\lambda ~ 2200, and 2.96-4.12 microns with \lambda/\Delta\lambda ~ 800. Telluric absorption features were removed from the data using Vega as the spectral standard, in lieu of solar-type stars. This allowed us to preserve and identify weak solar features in the Mars reflectance spectrum by comparison with ATMOS spectra [1].

The spatial distribution of south polar CO₂ ice was mapped using the measured 2.28 and 2.32 micron "forbidden" spectral features in solid CO₂, which have been shown to be sensitive to grain size [2]. The low latitude boundary of the CO₂ ice region appears to be diurnally influenced, indicating either a fine-frost component on the surface, or morning CO₂ ice clouds. Band depth maps near 3 microns confirm the morphology of a persistent H₂O ice cloud band centered near 20 degrees North latitude, which was observed nearly simultaneously by MGS/TES and found to extend over all longitudes [3].

[1] Kurucz, R. (1999), private communication. [2] Calvin, W. M. and T. Z. Martin (1994), J. Geophys. Res., v99, 21143-21152. [3] Pearl, J. C., M. D. Smith, B. J. Conrath, J. L. Bandfield and P. R. Christensen (1999), B.A.A.S., v31, 1190.

The author(s) of this abstract have provided an email address for comments about the abstract: dave.glenar@gsfc.nasa.gov