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J.F. Bell III (Cornell University), Athena Science Team
Multispectral images from 400 to 1000 nm from the Mars Exploration Rover Spirit and Opportunity Pancams have provided new information on the morphology, physical properties, and mineralogy of rocks and soils at Gusev and Meridiani and have played a critical role in helping to choose specific targets for detailed compositional analyses using the rovers' arm instruments. Images within the Gusev plains reveal a rock-strewn surface interspersed with moderate- to high-albedo fine-grained deposits occurring in part as drifts or in small circular hollows. Optically thick coverings or coatings of fine-grained ferric-rich dust dominate most bright soil and rock surfaces. Spectra of some darker rock surfaces show near-IR signatures consistent with mafic silicates like pyroxene or olivine. Imaging in the Columbia Hills reveals evidence for outcrop, layered materials, and a different style of physical and/or chemical weathering of some rocks than in the plains. At Meridiani, images within Eagle crater and in the plains during the traverse to Endurance crater reveal a low-albedo, generally flat and rock-free surface. Outcrops of higher-albedo, red, laminated rocks are observed within and around small craters, riftlike cracks in the plains, and well into Endurance crater. Fine-grained materials include dark ferrous-Fe rich basaltic sand, angular rock clasts, bright dust, and mm-size, low- and high-albedo spherical granules (spherules) that occur within and near the bright outcrop. Spectra of the low-albedo sand, small rock clasts, and one larger dark rock found on the plains show near-IR signatures consistent with the presence of pyroxene or olivine. Spectra of the dark spherules are consistent with the presence of crystalline ferric oxides/oxyhydroxides, supporting their interpretation as concretions. Bright spherule spectra are consistent with dark spherules covered or coated by nanocrystalline ferric-rich dust. Spectra of the laminated outcrop materials indicate the presence of ferric-rich minerals even within the spherule-free parts of these deposits.
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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.