NASA's Opportunity rover has arrived at Endeavour crater, a sweeping impact site fraught with clay minerals that could signal a wetter, more habitable environment existed on ancient Mars, the space agency announced Wednesday.

The west rim of Endeavour crater on Mars was collected on Aug. 6. Credit: NASA/JPL-Caltech/Cornell/ASU

"Our arrival at this destination is a reminder that these rovers have continued far beyond the original three-month mission," said John Callas, Opportunity's project manager at the Jet Propulsion Laboratory in Pasadena, Calif.

Opportunity confirmed its location along Endeavour's rim Tuesday. Officials named the site Spirit Point after Opportunity's sister rover, which stopped communicating with Earth in March 2010.

NASA's Mars Reconnaissance Orbiter, a sharp-eyed satellite circling more than 150 miles above the planet, spotted signs of clay minerals around the crater's rim and compelled rover managers to order Opportunity to investigate.

The clay minerals likely formed in ancient watery environments that may have been mild enough to be suitable for life.

"We're soon going to get the opportunity to sample a rock type the rovers haven't seen yet," said Matthew Golombek, a rover science team member at JPL.

Opportunity previously discovered evidence of liquid water at other craters in Meridiani Planum, an expansive dusty plain pockmarked with impact sites, rock outcrops and sand dunes. But Endeavour could hold clues pointing to a less acidic, more ancient environment than from the rocks encountered by Opportunity so far.

Images taken by Opportunity in late July. It shows a more distant view of the rims of Endeavour and Iazu craters. Credit: NASA/JPL-Caltech/Cornell/ASU/Marco Di Lorenzo/Kenneth Kremer

Opportunity studied Victoria crater for nearly two years, traveling inside the depression to closely observe rock layers. The most interesting science targets at Endeavour are along the crater's rim, according to researchers.

With a diameter of 14 miles, Endeavour crater is 25 times larger than Victoria. The crater measures about 1,000 feet deep.

The rover's exploration of Endeavour crater will begin at a feature named Cape York, an outcrop that appears surrounded by clay-bearing minerals. Spirit Point, the robot's current location, is at the southern flank of Cape York, according to Guy Webster, a NASA spokesperson.

The next destination is likely Cape Tribulation, a higher rim fragment harboring clay minerals.

Scientists have assigned the crater's features names after places visited by British Royal Navy Capt. James Cook during his exploration of the Pacific Ocean aboard the HMS Endeavour.

The Mars Reconnaissance Orbiter's context camera took this image of Endeavour crater from orbit. Credit: NASA/JPL-Caltech/MSSS
 
Mineral mappers aboard the MRO spacecraft helped identify regions around Endeavour crater saturated with clays. MRO's high-resolution telescopic camera provided detailed topographic and terrain maps of the scientific study sites.

Opportunity has traveled more than 20 miles since landing on Mars in January 2004. The Spirit and Opportunity rovers were each designed to last three months on the surface.

"NASA is continuing to write remarkable chapters in our nation's story of exploration with discoveries on Mars and trips to an array of challenging new destinations," said NASA Administrator Charlie Bolden. "Opportunity's findings and data from the upcoming Mars Science Laboratory will play a key role in making possible future human missions to Mars and other places where humans have not yet been."

The Mars Science Laboratory's Curiosity rover is scheduled to launch Nov. 25 and arrive at the Red Planet in August 2012. It will land inside Gale crater and start to climb up a 15,000-foot-tall mountain containing layered rocks, clays and sulfates believed to have formed in the presence of water.

Curiosity will help determine whether Mars was ever hospitable for life.