HR: 14:45h
AN: P13B-05    [Abstracts]
TI: Visible to Near-IR Spectral Properties of Rocks and Soils at Gusev and Meridiani from the Mars Exploration Rover Pancams
AU: * Bell, J F
EM: jfb8@cornell.edu
AF: Cornell University, Dept. of Astronomy, Ithaca, NY 14853-6801
AB: Mars Exploration Rover Pancam multispectral images of a wide range of rock and soil targets were acquired using as many as 11 narrowband filters with central wavelengths from 432 to 1009 nm. These images were acquired in order to characterize the overall color properties of materials at the Gusev and Meridiani landing sites, to constrain the iron-bearing mineralogy of these materials based on the nature of crystalline and/or nanophase $Fe^{3+}$ (ferric) absorptions in the visible to near-IR in altered materials and $Fe^{2+}$ (ferrous) absorptions in the near-IR from less-altered volcanic materials, and to aid in the selection of specific targets for detailed chemical and mineralogic investigations using the rovers' arm instruments. At Gusev during the plains traverse to the Columbia Hills, most bright soil and rock surfaces appear covered or coated by optically thick fine-grained ferric-iron rich dust. Spectra of some darker rock surfaces, including regions that were brushed or drilled by the RAT, show near-IR signatures consistent with ferrous silicates like pyroxene or olivine. Since Spirit's arrival in the Columbia Hills, Pancam images have revealed evidence for some intrinsically less dusty or less altered rock surfaces, as well as isolated occurrences of more crystalline ferric signatures that may be indicative of enhanced weathering or alteration relative to materials in the plains. At Meridiani during the exploration of Eagle crater and during the traverse to Endurance crater, a wide range of visible to near-IR spectral properties was identified among small rock clasts and spherules. For example, spectra of dark sand, some dark rock clasts, and one larger dark rock found on the plains show spectra consistent with the presence of pyroxene or olivine. Spectra of dark spherules are consistent with the presence of crystalline ferric oxides/oxyhydroxides. Bright materials, including windblown dust, bright spherules, and the sulfur-rich laminated outcrop deposits, have Pancam spectra that indicate the presence of poorly-crystalline or nanophase ferric-iron rich minerals. Within Endurance crater, Pancam spectra reveal evidence for outcrop and spherule materials similar to those found in Eagle and during the plains traverse, plus additional color/spectral units associated with cm-scale layering within the crater walls, a morphologically-different class of spherules, isolated blocks of wall material and/or crater ejecta, and coatings and fractures/veins within rocks in the lower part of the stratigraphic sequence investigated by Opportunity.
DE: 6062 Satellites
DE: 6225 Mars
DE: 3672 Planetary mineralogy and petrology (5410)
SC: Planetary Sciences [P]
MN: 2004 AGU Fall Meeting