US: NASA's Mars Rover Opportunity has found bright veins of a mineral, which appears to be gypsum, deposited on Mars. Analysis of the vein will help improve understanding of the history of wet environments on the planet.
"This tells a slam-dunk story that water flowed through underground fractures in the rock," said Steve Squyres of Cornell University, principal 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."
The latest findings by Opportunity were presented on 7 December 2011 at the American Geophysical Union's conference in San Francisco.
The vein examined most closely by Opportunity is about 1cm – 2cm wide, 40cm to 50cm long, and it protrudes slightly higher than the bedrock on either side of it. Observations by the rover reveal this vein and others like it within an apron surrounding a segment of the rim of Endeavour Crater.
In November 2011 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 sulphur, in a ratio pointing to relatively pure calcium sulphate. The multi-filter data from the camera suggest gypsum, a hydrated calcium sulphate.
Observations from orbit have detected gypsum on Mars previously. A dune field of windblown gypsum on far northern Mars resembles the glistening gypsum dunes in White Sands National Monument in New Mexico, US. However the Homestake vein is the first time the mineral has been spotted where it formed.
