HR: 1340h
AN: P13D-1561    [Abstracts]
TI: Comparisons between phyllosilicate-bearing strata at Mawrth Vallis and Terra Meridiani
AU: * Farrand, W H
EM: farrand@spacescience.org
AF: Space Science Institute, 4750 Walnut Street, Boulder, CO 80301, United States
AU: Rice, J W
EM: jim.rice@asu.edu
AF: Arizona State University, Moeur Building, Tempe, AZ 85287, United States
AU: Glotch, T D
EM: tglotch@notes.cc.sunysb.edu
AF: State University of New York Stony Brook, 255 Earth and Space Sciences, Stony Brook, NY 11794, United States
AB: Recent observations of ancient terrains with phyllosilicate minerals and somewhat younger terrains with layered sulfate-rich rocks have led to the suggestion of reordering the nomenclature of Martian geologic epochs so that they are associated with the time periods when these materials were formed. The earlier "Phyllosian" era would be associated with the time that the phyllosilicate minerals were formed. This would correspond to the current early Noachian. This would be followed by the "Theiikian" era which is when the sulfate minerals were formed and corresponds to the late Noachian/early Hesperian. Large exposures of phyllosilicate-rich rocks have been observed at a number of areas including the Mawrth Vallis region. Sulfate-rich rocks have been directly sampled at Meridiani Planum by the Opportunity rover and mapped from orbit. Several distinct spectral/stratigraphic units have been mapped at Mawrth Vallis based on the presence of H2O and metal-OH absorption features. These include materials with a 2.2 micrometer Al-OH feature, nominally attributed to montmorillonite, with a 2.3 micrometer Mg or Fe-OH feature, nominally attributed to nontronite, and materials with a 1.9 micrometer H2O but no discernable metal-OH band. Sulfate minerals have not been identified at Mawrth Vallis. These spectral units, based on short-wave infrared features, also tend to have distinct visible and near infrared color properties which are mappable, at higher spatial resolutions, by color HRSC data. Examination of these color units with high resolution HiRISE images indicates that they have distinct textural properties as well. The recent discovery of exposures of phyllosilicate-bearing rocks in eastern Terra Meridiani invites comparisons with the phyllosilicate-bearing rocks in Mawrth Vallis. Initial examination of HiRISE images of the eastern Meridiani phyllosilicate region indicates different surface textures for the Meridiani phyllosilicate region versus the Mawrth Vallis region. The latter has smooth to fractured surfaces while the former has a rougher, more knobby texture. Multispectral, hyperspectral, and thermal emissivity characteristics of the two regions are also being examined using color HRSC, hyperspectral OMEGA, CRISM, and TES and multispectral THEMIS data.
DE: 5410 Composition (1060, 3672)
DE: 5464 Remote sensing
DE: 5470 Surface materials and properties
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting