From Scientific American, 16 Aug 2011

After a long journey, the Mars rover Opportunity has arrived at Endeavour Crater, a giant indentation with some interesting geology. It took Opportunity almost three years to cover the 20 kilometers to Endeavour Crater. That's an average pace well below the crawling speed of an earthworm.

Rover operators on Earth drove Opportunity cautiously and made several stops along the way to check out interesting Martian surface features. And now they have a potential treasure trove in Endeavour Crater. A NASA orbiter has spotted the signature of clays and other hydrated minerals in and around Endeavour. Those materials form in watery environments and presumably trace back to a time when Mars was much warmer and wetter than it is now. Perhaps the Red Planet was even conducive to life. Opportunity's instruments may be able to uncover what Mars was like when those minerals formed.

Whatever work the rover is able to do at Endeavour Crater is a bonus for NASA, which assigned three-month missions to Opportunity and its now defunct twin rover, Spirit. That was more than seven years ago. Slowly but surely, Opportunity keeps rolling along.