From views of spectacularly layered cliff walls and sulfate-rich rock to the detection of tiny hematite "blueberries" and probable meteor debris, the Mars rover Opportunity's two-year exploration of Victoria Crater has yielded a wealth of information about the planet's geologic history -- and supported previous findings indicating that water once flowed on the planet's surface.

As Opportunity heads south toward Endeavor Crater, 13.5 kilometers (7.3 miles) away, a paper in the May 22 issue of the journal Science reports on the major findings from Victoria. The giant impact crater -- 750 meters (820 yards) wide and 75 meters (82 yards) deep -- gave scientists an unparalleled view into the planet's evolution, revealing evidence of a windy, wet and dynamic past.

The paper is a broad summary of observations that were released incrementally as they were made over the last two years, said Steve Squyres, principal investigator for NASA's Mars Exploration Rover mission and Cornell's Goldwin Smith Professor of Astronomy.

Many of those observations -- of hematite spheres (the blueberries), sulfate-rich sandstone and small chunks of rock containing kamacite, troilite and other minerals commonly found in meteorites -- are consistent with Opportunity's findings across Meridiani Planum, the rocky plateau the size of Oklahoma where the rover landed Jan. 24, 2004.

"It shows that the processes that we investigated in detail for the first time at Endurance Crater [where Opportunity spent six months in 2004] are regional in scale, [indicating that] the kinds of conclusions that we first reached at Endurance apply perhaps across Meridiani," said Squyres.

Still, there are a few key differences. The rim of Victoria Crater is about 30 meters (32.8 yards) higher than the rim of Endurance, said Squyres; and as the rover drove south toward Victoria the hematite blueberries in the soil became ever fewer and smaller. Rocks deep inside the crater, however, contained big blueberries -- indicating that the rocks higher up had less interaction with water -- and thus the water's source was likely underground.

Detailed analysis of the Victoria data will occupy researchers for years to come, said Jim Bell, Cornell professor of astronomy and leader of the Pancam color camera team for the mission.

On the other side of the planet in Gusev Crater, meanwhile, Opportunity's twin rover Spirit's computer had an unexplained reboot in April, causing consternation at the Jet Propulsion Lab, a division of the California Institute of Technology in Pasadena, Calif., that manages the Mars Exploration Rover Project for NASA. That problem hasn't recurred, but the rover is now stuck, possibly belly-deep, in a patch of fine Martian soil.

"The vehicle seems to be in a unique combination of soft, sandy material and slopes that we haven't encountered yet," said Bell. "Neither one has been particularly problematic in the past, but the combination of the two has us bogged down."

In 2005 Opportunity faced a similar quandary when it found itself mired down for a month in a sand trap named Purgatory Dune.

"We're not calling this purgatory for Spirit yet, but it has that potential," Bell said. Rover team members -- including Cornell senior research associate Rob Sullivan, who played a leading role in freeing Opportunity from Purgatory Dune -- are using data from the rover and from NASA's Mars Odyssey orbiter and Mars Reconnaissance Orbiter to plan Spirit's escape.