HR: 08:30h
AN: P21C-03 INVITED    [Abstracts]
TI: Origin and Evolution of the Layered Sulfate-Rich Rocks in Meridiani Planum, Mars
AU: * Arvidson, R E
EM: arvidson@wunder.wustl.edu
AF: Washington University, 1 Brookings Drive, Campus Box 1169, St. Louis, MO 63130, United States
AB: Opportunity rover observations show that Meridiani Planum has extensive exposures of sulfate-rich dirty sandstones partially covered by a mix of wind-blown basaltic sand, dust, and a lag deposit of 1 to 5 mm diameter hematitic concretions. The dirty sandstones are interpreted to have formed in an acid-sulfate evaporative lacustrine system that left behind sulfate-rich muds with a siliciclastic component. Erosion by wind and water produced sandstones that were then cemented and diagenetically altered by rising groundwater. Subsequent wind erosion of these deposits and associated advection of basaltic sand onto the outcrops produced the surfaces encountered during the rover's traverses. On a regional scale these sulfate-rich deposits are up to several kilometers in thickness, extend over several hundred thousand square kilometers, and unconformably overlie the fluvially dissected Noachian cratered terrain. Both OMEGA and CRISM hyperspectral data show clear evidence for the presence of phyllosilicate minerals in the cratered terrains adjacent to the sulfate deposits, but not within the sulfate section proper. The ensemble of evidence indicates a change in Meridiani Planum from fluvial erosion and formation of phyllosilicate minerals to deposition of evaporite deposits associated with an acid-sulfate aqueous system. This change is interpreted to be due to a major climatic shift in which a relatively vigorous hydrologic system with extensive neutral rain and snowfall changed to more arid conditions in which a regional-scale acid sulfate groundwater system emerged in Meridiani Planum with enough of a hydrostatic head to produce and retain 1 to 3 km of sulfate-rich deposits.
DE: 5400 PLANETARY SCIENCES: SOLID SURFACE PLANETS
DE: 5470 Surface materials and properties
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting