Mars rover driving out of crater

Opportunity drove into Victoria Crater last year

Nasa's robotic rover Opportunity is driving out of a giant crater on Mars nearly a year after its dangerous descent to examine exposed bedrock.

The 800m-wide Victoria Crater lies on the Red Planet's Meridiani Plains.

The impact depression has high walls with layers of exposed rock that should reveal clues to Mars' geological past.

Nasa said that engineers had 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 long past their original 90-day mission.