HR: 0830h
AN: P21B-0049    [PDF]
TI: TES Mineralogy in the Wings of the CO$_{2}$ Band. Constraining the Mineralogy of Type 2 Terrain.
AU: * Noe Dobrea, E Z
EM: ezn1@cornell.edu
AF: Cornell University, 406 Space Sciences Building Cornell University, Ithaca, NY 14853 United States
AU: Bell, J F
EM: jfb8@cornell.edu
AF: Cornell University, 406 Space Sciences Building Cornell University, Ithaca, NY 14853 United States
AU: Wolff, M J
EM: wolff@colorado.edu
AF: Space Science Institute, Augusta, GA, Space Science Institute 2039 Pheasant Creek Drive, Augusta, GA 30907 United States
AU: Smith, M D
EM: Michael.D.Smith@nasa.gov
AF: NASA Goddard Space Flight Center, Code 693 NASA Goddard Space Flight Center, Greenbelt, MD 20771 United States
AB: In search for further telltale mineralogical absorptions to constrain the mineralogy of the Type 2 terrain, we have corrected for the atmospheric absorption in the wings of the 15-$\mu$ m CO$_{2}$ band. Bandfield {\it et al.} (Science, Vol. 287, Issue 5458, pp. 1626-1630, 2000) identified two primary types of terrain in TES spectra, one associated primarily with highland material (Type 1 terrain), and the second associated with lowland material (Type 2 terrain). The spectrum of Type 1 terrain was shown to match that of basalt, whereas the best match for the spectrum of Type 2 terrain was shown to be basaltic andesite. Wyatt and McSween (Nature, Volume 417, Issue 6886, pp. 263-266, 2002) later showed that the spectrum of weathered basalt could provide an equally good match for the Type 2 terrain. Most recently, Ruff (Mars 6, \#3258, 2003) searched the 530 cm$^{-1}$ region for evidence of clay-type minerals such as Montmorillonite, Nontronite, and Fe-smectite, and found no absorption whose global distribution could correlate to that of the Type 2 terrain. Although the 530 cm$^{-1}$ region does contain mineralogical absorptions of interest, it is not the limit, and additional absorptions by plausible alteration minerals can occur further into the shoulders of the CO$_{2}$ band. In this work, we corrected the 500-600 cm$^{-1}$ region for the effect of the low wavenumber CO$_{2}$ wing. Because such atmospheric work requires accurate knowledge of the wavenumbers in the spectra, we recalibrated the TES wavenumbers using the atmospheric absorption of water vapor at high and low wavenumbers, and CO$_{2}$ hot- and isotope- bands at the intermediate wavenumbers. This method showed discrepancies (which increased at large wavenumbers) between our results and those reported by the TES team, leading us to adopt our calibrated wavenumbers for this work. To correct for the wings in the CO$_{2}$ band, we used the correlated-k method along with the retrievals of aerosol loading and vertical temperature distributions that were originally described by Conrath {\it et al.} (JGR, V.105, E4, pp.9509-9520, 2000) and provided by the PDS. We applied this correction and a band-finding algorithm to the data from the first 3000 orbits. Preliminary results suggest the presence of an absorption band centered at 563 cm$^{-1}$. This absorption exists in some sheet silicates such as smectite clays ({\it ie:} kaolinite, dickite) and micas (muscovite), some iron oxides ({\it ie:} hematite, magnetite), and some phosphates (apatite). Further work will involve the inclusion of more observations, mapping of this feature index and a search for features in the higher wavenumber wing of the CO$_{2}$ band.
DE: 3672 Planetary mineralogy and petrology (5410)
DE: 5410 Composition
DE: 5464 Remote sensing
DE: 5470 Surface materials and properties
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2003 Fall Meeting