Credit: NASA/JPL–CALTECH

Almost a year after it drove into the Victoria Crater on Mars, NASA's Opportunity rover last week made its way back out. Opportunity left by the same route it entered by, allowing it to study its old tracks (pictured) for any signs of changes during the past 11 months.

During its time in the 800-metre-wide, 70-metre-deep crater, the rover took detailed photographs of rocky outcrops and conducted chemical analyses that suggest the crater was once soaked in water. Opportunity will next study rocks strewn across the surrounding plains. Scientists hope that these represent several types of rock scattered by earlier impacts.

Opportunity has spent more than 1,600 martian days exploring and is showing its age. Its robotic arm is kept permanently extended owing to fears about the health of its 'shoulder' motor, and engineers recently noted an electric-current spike similar to that seen in Opportunity's twin rover Spirit shortly before it lost the use of one of its wheels.