Geologic Analysis of a Possible Oasis and Environs in the Valles Marineris, Mars

Details Geologic Analysis of a Possible Oasis and Environs in the Valles Marineris, Mars Geologic Analysis of a Possible Oasis and Environs in the Valles Marineris, Mars

Dec 2002

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002agufm.p62a0361g&link_type=abstract

American Geophysical Union, Fall Meeting 2002, abstract #P62A-0361

Mathematics

Logic

5464 Remote Sensing, 5470 Surface Materials And Properties, 6225 Mars

Scientific paper

We used Mars Global Surveyor data from TES, MOC, and MOLA to examine the geologic history of a region of interior layered deposits on the floor of western Candor Chasma in the Valles Marineris, Mars. This site was characterized by Geissler et al. (1993, Icarus 106) as having an unusual reddish color in multispectral images from Viking and Phobos missions. The red color was associated with two 20-km-long depressions and was thought to indicate the presence of crystalline ferric oxides (possibly hematite) in the layered deposits. Assuming that water was required to form the iron oxides via aqueous or hydrothermal alteration, these depressions may mark the site of a local oasis involving ponding or groundwater seepage in the canyon. Thermal inertia and dust index images from TES data of west Candor Chasma indicate that mantling and obscuration of local outcrops is not significant in the region of the possible oasis. To characterize the mineralogy of this area, we use multiple-endmember spectral mixture analysis (MESMA) to deconvolve TES emissivity data relative to laboratory spectra of minerals. This method identifies the minimum number of components (4 to 5) required to model the spectrum of each pixel in the spectral ranges of 307-507 cm-1 and 825-1301 cm-1 (66 TES channels) through iterative comparisons to a 33-component mineral spectral library. This library, adapted from that of ASU, includes pyroxenes, plagioclase feldspars, clays, micas, amphiboles, sulfates, carbonates, olivines, K-spar, gray hematite, and volcanic glass, plus 5 atmospheric endmembers and a blackbody. Although nanophase red hematite is undistinguished at TES wavelengths, mineral abundance maps indicate the presence of other Fe-rich minerals (such as nontronite and Fe-smectite) at this site. Gray hematite, hi-Ca clinopyroxene, Fe-rich olivine, and hi-Ca plagioclase minerals are also observed within layered deposits in the canyon walls and interior, as well as in dark materials at the base of canyon walls. These results suggest that we are mapping sites of alteration and volcanism in west Candor Chasma with the TES data. We are currently performing photoclinometric modeling of coregistered MOC (6 m/pixel) and MOLA (500 m/pixel) data via the method of Soderblom et al. (2002, LPS\ #1254) to evaluate the orientation and possible origin of this layered deposit.

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