Cracking El Capitan's Secrets

Microscopic photographs of a Mars rock taken by NASA's Opportunity rover have triggered excitement among scientists, even if they aren't unanimous on exactly what they're seeing.

The images, posted on Jet Propulsion Laboratory's Mars rovers Web site, show a highly detailed surface on a rock dubbed "El Capitan" that has been undergoing examination by the robot geologist.

"They are just very beautiful things and it's not at all clear that we understand what we're looking at," mission official Rob Manning said in a teleconference with reporters on Monday.

"There is a lot of enthusiasm, probably as much enthusiasm as we've ever had by the science team and a lot of intense discussions over these last several days."

The $820 million mission of Opportunity and the twin rover Spirit is aimed at finding geologic evidence that dusty, frigid Mars was once a wetter place where life could have taken hold.

"El Capitan" was designated the top target for close-up study after a general assessment of the outcropping from a distance. The layered rock generated debate about whether it was formed volcanically, by deposition of sediments, or involved mineral growth or wind-created structures.

"Once we got close, the images are much more striking, and although the science team is very reluctant to make any decisions about what they're looking at, there's a lot of information in the pictures they've been looking at," Manning said.

It was not certain when scientists would comment on their findings. A teleconference was set for Tuesday and the next formal press conference was scheduled for Thursday at JPL in Pasadena.

Manning predicted that Opportunity would spend "a fair amount of time" at the outcrop before leaving the area to search for other sites to explore in an area known as Meridiani Planum.

"There's just too much excitement, too much to see," he said.

On the other side of Mars in Gusev crater, Spirit had left a trench it dug last week for study of subsurface soil and was en route to a new site dubbed "Middle Ground."

By John Antczak