NASA's Mars Exploration rover Opportunity is heading back out to the Red Planet's surrounding plains nearly one year after descending into a large Martian crater to examine exposed ancient rock layers. Having completed its job in the crater, Opportunity is now preparing to inspect loose cobbles on the plains. Some of these rocks, approximately fist-size and larger, were thrown long distances when objects hitting Mars blasted craters deeper than Victoria into the Red Planet. Opportunity has driven past scores of cobbles but examined only a few. Opportunity entered Victoria Crater on Sept. 11, 2007, after a year of scouting from the rim. Once a drivable inner slope was identified, the rover used contact instruments on its robotic arm to inspect the composition and textures of accessible layers. The rover then drove close to the base of a cliff called "Cape Verde," part of the crater rim, to capture detailed images of a stack of layers 20 feet tall. The information Opportunity has returned about the layers in Victoria suggest the sediments were deposited by wind and then altered by groundwater.