HR: 1340h
AN: P23B-1356    [Abstracts]
TI: The Case for CO2 on Titan From the VIMS Reflectance Spectra
AU: * McCord, T B
EM: mccordtb@aol.com
AF: Bear Fight Center, 22 Fiddler's Road; P.O. Box 667, Winthrop, WA 98862, United States
AU: Hayne, P
AF: Bear Fight Center, 22 Fiddler's Road; P.O. Box 667, Winthrop, WA 98862, United States
AU: Hayne, P
AF: University of California Los Angeles, Dept. of Earth and Space Science, Los Angeles, CA 90095, United States
AU: Combe, J
AF: Bear Fight Center, 22 Fiddler's Road; P.O. Box 667, Winthrop, WA 98862, United States
AU: Hansen, G B
EM: ghansen@rad.geology.washington.edu
AF: University of Washington, Dept. of Earth and Space Science, Seattle, WA 98195, United States
AB: The Cassini Visual and IR Mapping Spectrometer (VIMS) is returning reflectance spectra of Titan's surface and atmosphere. The Titan atmosphere allows viewing of the surface only in a few narrow spectral windows in the near IR due to methane absorptions, and particulate scattering affects even these windows. We have analyzed many of the VIMS Titan data sets to determine what can be said about the surface composition of Titan from these data [McCord et al., Pl. and Sp. Sci., 2006; McCord et al., Icarus, in press]. One particularly interesting recent discovery using VIMS data is three-fold evidence of CO2 frost on the surface. First, it is possible to model the surface spectral units globally using Spectral Mixing Analysis and seven IR spectral windows with a combination of CO2, H2O, atmospheric scattering, an unknown bright material at 2 μm, and a dark spectrally-neutral material. Secondly, for at least the area called Tui Regio, the spectral contrast between the two 2.8-μm subwindows is matched by CO2 but not by other potential candidates, and thirdly a weak absorption near 4.92 μm for Tui Regio is very close to matching a CO2 absorption. No CO2 absorption features are missing where they should appear in the spectrum within the windows available. CO2 has been suggested before as a likely component of Titan's surface, but this is the first direct spectral absorption evidence.
DE: 5470 Surface materials and properties
DE: 6281 Titan
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting