PASADENA, Calif. (AP) - The plucky Mars rover Opportunity is driving out of a giant crater nearly a year after a dangerous descent to examine exposed bedrock.

NASA said Tuesday that engineers noticed a power surge in Opportunity's left front wheel and decided to pull it out of the crater before it got stuck. Its twin rover, Spirit, lost function in its right front wheel in 2006 after a similar surge.

Opportunity descended into Victoria Crater last September and inspected bright rock layers. Once it emerges, it will study loose rocks on the equatorial plains.

Opportunity and Spirit landed on Mars in 2004 and have operated beyond their original 90-day mission.