NASA's Rover Opportunity, currently traipsing across the surface of Mars, has arrived at the rim of the Victoria Crater, a gash in the planet's surface over half a mile wide and 230 feet deep.

The rover has been heading for the crater for more than half its time on the planet. Its journey as been interrupted by "frequent stops to examine intriguing rocks" and even a sand ripple, that kept the rover pinned down for more than five weeks.

Scientists hope the crater, which exposes so much Martian geology, will help them understand even more about the historical environment of the planet. Previously, NASA described it as a "scientific treasure trove".

Steve Squyres of Cornell University, principal investigator for NASA's twin rovers Opportunity and Spirit described the arrival as a geologist's dream come true.

"Those layers of rock, if we can get to them, will tell us new stories about the environmental conditions long ago. We especially want to learn whether the wet era that we found recorded in the rocks closer to the landing site extended farther back in time," he said.

Meanwhile, Opportunity's twin, Spirit, is still trying to soak up as much sun as possible to get it through the southern hemisphere's winter. ®

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