PASADENA, Calif. (AP) – NASA’s Mars rover Spirit has begun driving in reverse to overcome a balky front wheel, but engineers expect it to keep covering Martian ground, mission officials said Friday.

The new driving technique was detailed as scientists at the Jet Propulsion Laboratory revealed that the six-wheeled Spirit had finally discovered a rock outcrop, a formation offering the potential for layered rocks that could give geologists a view far into Mars’ geologic past.

Spirit’s twin, Opportunity, fortuitously landed next to such an outcrop in January. Opportunity quickly found a wealth of evidence that the site in the Meridiani Planum region was once saturated with water, and conditions there could have been suitable for life.

On the other side of the planet, Spirit had to make a long trek across the plains of a vast crater before literally rolling over the outcrop as the rover was preparing to begin climbing into a set of hills.

The long drive apparently took a toll on Spirit’s right front wheel, which began to draw more and more electrical current, a sign of resistance in the mechanism.

Efforts to use heating and rest to get lubrication to move back into the mechanism achieved only small improvement, so engineers decided to put the rover in reverse.

“Right now it is still capable of performing all tasks that we ask it to do,” said engineer Joe Melko, who noted that the rover has gone more than six times beyond its design life.

Moving backward allows Spirit to drag the right front wheel while driving itself with its five other wheels. Slightly turning some wheels allows the rover to maintain a straight course.

Showing a picture of the outcrop beneath Spirit’s wheels, mission science team member Matt Golombek said the good news is that Spirit doesn’t have to go much farther.

“Outcrop is the currency that geologists use,” he said. “It’s contiguous bodies of rock that really contain the secrets that we want to unveil. And for the entire mission, 190 sols (Martian days), we’ve been seeking it and we finally found it.”