HR: 14:25h
AN: P13E-04    [Abstracts]
TI: Thermal Infrared Studies of Chloride Salts; Implications for Mars
AU: * Baldridge, A M
EM: alice.baldridge@asu.edu
AF: School of Earth and Space Exploration, Arizona State University MC 6305, Tempe, AZ 85287-6305, United States
AU: Osterloo, M M
EM: osterloo@higp.hawaii.edu
AF: Hawaii Institute of Geophysics and Planetology, University of Hawaii 1680 East-West Rd, POST 517, Honolulu, HI 96822, United States
AU: Christensen, P R
EM: phil.christensen@asu.edu
AF: School of Earth and Space Exploration, Arizona State University MC 6305, Tempe, AZ 85287-6305, United States
AB: Morphological and spectral evidence supporting the past occurrence of widespread water on the surface of Mars continues to build. Furthermore, geochemical footprints of water are especially compelling. As a past reservoir of water receded, it would have left behind evaporitic chemistries specific to Martian water-rock interactions (e.g. chlorides, sulfates and phyllosilicates). To understand the extent and abundance of past water, the detection of such minerals is key. In support of both orbital and in situ thermal infrared (TIR) observations, we have examined the TIR behavior of chloride minerals. In the thermal infrared, most minerals are identified based on characteristic absorption features. However, chloride detection is particularly challenging because these minerals are transparent over much of the infrared and therefore their identification must be based on the effect that they have on the spectra of coexisting materials. Additionally, the transparent nature of chlorides results in greybody (non-unit emissivity) behavior and consequently the standard calibration techniques to convert from radiance to emissivity produces a slope in the spectra. Here we discuss laboratory spectral studies including emission, reflectance, and transmission spectra of a suite of chloride minerals and mixtures. These studies are then used to interpret a spectrally distinct deposit identified with 2001 Odyssey Thermal Emission Imaging System (THEMIS) data in the low albedo, mid-to-low latitude, southern highlands of Mars which correspond to mid- late Noachian aged terrains and early Hesperian aged ridged plains units.
DE: 5220 Hydrothermal systems and weathering on other planets
DE: 5464 Remote sensing
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting