This week NASA revealed that Opportunity is currently examining veined rocks on the rim of an ancient crater named "Endeavor." The rover is examining the area, called "Matijevic Hill," and has found evidence of a wet environment in Mars' past, and a less acidic environment than was found earlier in the rover's mission.
Opportunity has now driven 35.46 kilometers (22.03 miles) since it landed on Mars in January 2004. The rover's primary mission was only three months long. It was to drive 600 meters (2,000 feet) and determine whether the area surrounding it had ever been wet. Opportunity has now operated for 36 times longer than what was originally planned. Since that time, researchers have driven the rover to successively larger craters, examining soil exposed from successively older layers of Mars.
"What's most important is not how long it has lasted or even how far it has driven, but how much exploration and scientific discovery Opportunity has accomplished," said John Callas, manager of the Mars Exploration Rover Project at NASA's Jet Propulsion Laboratory (JPL).
Opportunity's twin, the Spirit rover, also operated past its original mission, though it hasn't fared as well as Opportunity. In 2009 Spirit became stuck in soft soil, and communications with the rover ceased in 2010.
(Image courtesy NASA/JPL-Caltech/Cornell/Arizona State Univ.)