LOS ANGELES – The Mars rover Opportunity reached the rim of a deep crater Wednesday after an arduous 21-month trek, marking a milestone in its exploration for clues about the Martian past.
The rover beamed black-and-white images back to Earth showing the crater interior, complete with hanging rocky cliffs and rippling sand dunes on its floor.
"We made it!" said rover principal scientist Steve Squyres of Cornell University.
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The road to Victoria Crater, a half-mile wide and 230-foot-deep impact crater, was tough.
The six-wheeled Opportunity drove through what scientists called a "wasteland." At one point, it spent five weeks stuck hub-deep in a slippery sand dune before freeing itself.
Victoria, with its exposed walls of thickly layered rocks, is a treasure trove for scientists trying to determine whether the rocks were formed in shallow lakes, which might suggest the planet once could have been hospitable to life.
"The big payoff is getting to the rock record," said deputy principal investigator Ray Arvidson of Washington University in St. Louis.
Opportunity will spend a day looking for a more favorable spot around the rim to take a panorama of the vista. Meanwhile, scientists are plotting Opportunity's next move and analyzing the images to find the safest route for the rover to enter.
Opportunity and its twin, Spirit, have been exploring opposite sides of Mars since landing in 2004. Both uncovered geologic evidence of past water activity on the planet.
The rovers, managed by NASA's Jet Propulsion Laboratory in Pasadena, have outlasted their primary, three-month mission. This week, the space agency extended the rovers' mission for at least one more year.