Limestone outcrop?



Meridiani Planum is rife with deposits of a mineral called crystalline hematite, which usually forms in the presence of liquid water. Thanks to the robot, scientists have the tools to examine on-the-spot surface layers rich in hematite and an underlying geological feature of light-colored layered rock.

The small crater in which the robot rover now rests appears to have exposures of both, with soil that could be the hematite unit and an exposed outcropping of the lighter rock layer.

Speculation that such an outcrop could be limestone would give scientists the eureka they’ve been looking for -- clear evidence that water stayed in that location for a long, long time. And with water comes the prospect for biology.

http://www.space.com/missionlaunches/opportunity_update_040127.html



It was because these deposits at the other landing sites were white that led to the conclusion they were carbonate or sulfate. The expectation is that they are widespread on Mars. If accurate color imaging showed these outcrops at the Opportunity site were white the conclusion would be they are of the same composition of the white deposits at the other sites, thus carbonate or sulfate.

Bob Clark