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The Origin of Sulfate-Rich Bedrock at Meridiani Planum on Mars: Sedimentary Evaporite, Impact, or Volcanic?

Presenter: Thomas McCollom, University of Colorado, Boulder
When: February 27, 2006 11AM PST

The Mars Exploration Rover (MER) Opportunity has now explored bedrock exposed within several craters on Meridiani Planum on Mars. The MER team has interpreted the rocks to be sedimentary deposits composed of a combination of siliciclastic materials derived from basalt and sulfate salts precipitated from evaporation of intruding groundwater brines, with reworking of the deposits by eolian and fluvial processes. More recently, alternative scenarios have emerged suggesting the bedrocks may instead be attributable to a giant impact or emplacement of volcanic ash deposits that were subsequently altered by reaction with sulfur-rich volcanic vapors. Each of these alternatives has substantially different implications for the astrobiological potential of this location on Mars. This talk will review the three current hypotheses concerning the origin of the bedrock, and discuss how each scenario accounts for the MER observations including bulk chemistry, mineralogy, scale, and presence of bedding features.

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