After an arduous 21-month journey, the Mars rover Opportunity edged close enough to the rim of a large crater yesterday to send back its first photos of the bottom and rocky sides of the dramatic site. What they showed left researchers increasingly confident that their robotic explorer had reached a scientific gold mine that will dramatically increase their understanding of the planet's history.

NASA scientists said the rover came within about 15 feet of Victoria Crater's rim and was scheduled to climb over a small sand dune last night and stop right at the crater's edge.