PASADENA, Calif., Sept. 14 (UPI) -- NASA says researchers are struggling to identify and understand an image its long-lived rover Opportunity has returned of small spheres on the martian surface.
Spherical objects photographed at an outcrop Opportunity reached last week differ in several ways from iron-rich spherules -- nicknamed "blueberries" -- the rover found at its landing site in early 2004 and at many other locations since, NASA's Jet Propulsion Laboratory in Pasadena, Calif., reported Friday.
Preliminary analysis suggests the spheres, as big as 1/8 inch in diameter, do not appear to have the high iron content of martian blueberries, researchers said.
"This is one of the most extraordinary pictures from the whole mission," Opportunity's principal investigator, Steve Squyres of Cornell University, said. "Of course, we immediately thought of the blueberries, but this is something different. We never have seen such a dense accumulation of spherules in a rock outcrop on Mars.
"They seem to be crunchy on the outside, and softer in the middle," he said. "They are different in concentration. They are different in structure. They are different in composition. They are different in distribution.
"So, we have a wonderful geological puzzle in front of us."