Mars rock coatings puzzle scientists

PASADENA, Calif., March 24 (UPI) -- U.S. space scientists say a strange coating on Mars rocks discovered by the rover Opportunity near a crater has left them puzzled.

NASA said the rover spent six weeks investigating a crater dubbed Concepcion that was flagged in advance as a study target because it appears to be young.

The scientists said rocks ejected from the impact that formed the crater are chunks of the same type of bedrock Opportunity has seen at hundreds of locations since landing in January 2004 -- soft, sulfate-rich sandstone holding harder peppercorn-size dark spheres like berries in a muffin. NASA said the spheres, rich in iron, gained the nickname "blueberries."

"It was clear from the images that Opportunity took on the approach to Concepcion that there was strange stuff on lots of the rocks near the crater," said Steve Squyres of Cornell University, principal investigator for Opportunity. "There's dark, grayish material coating faces of the rocks and filling fractures in them. At least part of it is composed of blueberries jammed together as close as you could pack them. We've never seen anything like this before."

While scientists continue to ponder the new images, Opportunity is again moving toward its long-term destination, Endeavour Crater, which is now about a 7-mile drive.

"We want to get to Endeavour with a healthy rover," said Squyres. "It takes a compelling target for us to stop and study. And Concepcion was a compelling target."