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T.M. Hoefen, R.N. Clark (USGS), J.C. Pearl, M.D. Smith (NASA)
Over the past several years the Mars Global Surveyor Thermal Emission Spectrometer (TES) has collected data at 10 wavenumber sampling over most of Mars. Unique Spectral features in the TES data over the Nili Fossae region have been observed, leading to a series of targeted 5 wavenumber sampling, 286 channel mosaics. The region of interest, approximately 100 km by 130 km, is located on the south eastern corner of Nili Fossae. The TES spectra of this area show two Christiansen frequencies. One has a local maximum in emissivity at 451 wavenumbers (22.1 micron) with a corresponding minimum at 408 wavenumbers (24.4 micron). The second feature has a local maximum at 303 wavenumbers (33.0 micron) with a corresponding minimum at 292 wavenumbers (34.1 micron). A doublet complex occurs between the Christiansen frequencies with minima at 340 wavenumbers (29.4 micron) and 358 wavenumbers (27.8 micron) and a maximum at 377 wavenumbers (26.5 micron). Furthermore, the TES data in the area exhibit a band at 943 wavenumbers (10.6 micron). Preliminary comparisons with lab spectra show similarities to sulfides and olivine. The current best match to the TES spectra is a linear combination of one-third each pyrite, olivine and basalt. This assemblage is unusually high in pyrite compared with terrestrial environments, yet is consistent with the high sulfur abundances determined by the Pathfinder and Viking landers for the Martian Surface.
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