HR: 09:15h
AN: P11E-06    [Abstracts]
TI: A Thermal Infrared View of Altered Noachian Martian Crust
AU: * Michalski, J
EM: michalski@gmail.com
AF: California Institute of Technology, Jet Propulsion Lab, 4800 Oak Grove, Pasadena, CA 91109, United States
AU: Noe, E
EM: edobrea@msss.com
AF: California Institute of Technology, Jet Propulsion Lab, 4800 Oak Grove, Pasadena, CA 91109, United States
AU: Mustard, J
EM: john_mustard@brown.edu
AF: Brown University, 324 Brook St., Providence, RI 02912, United States
AU: Bibring, J
EM: bibring@ias.u-psud.fr
AF: Institut d'Astrophysique Spatiale, batiment 121, Orsay, 91405, France
AB: Exposures of altered, ancient Martian crust seemingly represent a distant epoch in Mars" history where aqueous surface processes were active and the planet may have been habitable. In this study, thermal infrared remote sensing data are analyzed in order to better understand these deposits and the geological conditions under which they formed. Three questions are addressed: 1) On surfaces where VNIR datasets detect clay minerals, do thermal IR datasets also detect clays? 2) Aside from clay minerals, what other minerals are detected in the clay-bearing deposits based on thermal IR spectroscopy? 3) What are the thermophysical properties of clay mineral-bearing deposits? Thermal IR data used include TES and THEMIS datasets. To date, one deposit has been detected in the Mawrth Vallis region where thermal IR spectra have features attributable to trioctahedral clay minerals - possibly serpentine. Many other deposits (elsewhere in Mawrth Vallis and the Nili Fossae region) have subtle features at long wavelengths (> 20 microns) suggestive of Mg- and/or Fe-bearing clay mineralogy. Most of the deposits that show strong clay mineral signatures in the VNIR have basaltic character in the thermal IR. Thermal inertia values for these altered deposits are consistent with a combination of bedrock and sand at subpixel levels - consistent with the interpretation of the clay minerals as bulk component of in situ bedrock. Understanding the bulk composition of ancient, clay-bearing bedrock is critical to unraveling the geologic formation mechanisms of these deposits and their significance related to ancient Martian climate and habitability. In the Mawrth Vallis region, the basaltic signatures from clay-bearing deposits are relatively weak. In the Nili Fossae region, the basaltic signatures are stronger with surface mineralogy dominated by plagioclase feldspar, pyroxene, and in some cases, olivine. At this point, it is difficult to strongly constrain the abundance of clay minerals in these deposits form thermal IR data because of the complicating considerations for particle size variation and surface texture. However, thermal IR results seem to indicate that the Mawrth Vallis deposits are more completely altered than the Nili Fossae deposits because the Nili Fossae deposits have a stronger signature of primary mineralogy. This is consistent with an interpretation of Mawrth Vallis deposits as altered, processes sediments or metasomatized pyroclastics. Clay-bearing materials in the Nili Fossae area might include ancient altered sediments as well, but could also include exposures of deep, partially altered igneous or metamorphic crust.
DE: 3617 Alteration and weathering processes (1039)
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting