Thursday, December 15, 2011

Slam-dunk’ Proof of Water on Mars

The Mars exploration rover Opportunity discovered a vein of the water-deposited mineral gypsum. "It's not uncommon on Earth," says Steve Squyres, "but on Mars it's the kind of thing that makes geologists jump out of their chairs." (Credit: NASA/JPL-Caltech/Cornell/ASU)

The vein, examined by NASA’s Mars exploration rover Opportunity, is about 16 to 20 inches long and the width of a human thumb, and protrudes slightly higher than the bedrock on either side of it. The vein and others like it are within an apron surrounding a segment of the rim of Endeavour Crater.

None like it were seen in the 20 miles (33 kilometers) of crater-pocked plains that Opportunity explored for 90 months before it reached Endeavour, nor in the higher ground of the rim.

“This tells a slam-dunk story that water flowed through underground fractures in the rock,” says Steve Squyres, professor of astronomy at Cornell University and principal scientific investigator for Opportunity.

“This stuff is a fairly pure chemical deposit that formed in place right where we see it. That can’t be said for other gypsum seen on Mars or for other water-related minerals Opportunity has found. It’s not uncommon on Earth, but on Mars, it’s the kind of thing that makes geologists jump out of their chairs.”

Last month, researchers used the microscopic imager and alpha particle X-ray spectrometer on the rover’s arm and multiple filters of the panoramic camera on the rover’s mast to examine the vein, which is informally named “Homestake.”

The spectrometer identified plentiful calcium and sulfur, in a ratio pointing to relatively pure calcium sulfate.

Calcium sulfate can exist in many forms, varying by how much water is bound into the mineral’s crystalline structure. The multifilter data from the camera suggest gypsum, a hydrated calcium sulfate. On Earth, gypsum is used for making drywall and plaster of Paris.

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