After more than eight years roaming Mars, the NASA rover Opportunity is still making discoveries.

Scientists said Tuesday the six-wheel, solar-powered vehicle has uncovered hints of clay minerals in outcrops along the western rim of a huge crater in the Martian southern hemisphere.

Clay minerals are important because they hold clues about the Martian climate. Studying them should help scientists determine whether surface conditions in the past could have been favorable for life. Until now, their presence has been spotted by orbiting spacecraft.

Results were released at the American Geophysical Union meeting in San Francisco.

Opportunity will stay at its current spot for several more months before heading south to an area believed to have a motherlode of clay minerals.

Opportunity landed in 2004 and outlasted its original, three-month mission.