Nasa's Opportunity Rover Completes 11 Years on Mars

Nasa's Mars Opportunity rover has celebrated its 11th anniversary on the Red Planet, marking the milestone with a stunning panorama of a Martian crater.

The panorama from one of the highest elevations that Opportunity has reached in its 11 years on Mars includes the US flag at the summit, the US space agency said.

The view is from the top of "Cape Tribulation," a raised section of the rim of Endeavour Crater. The panorama spans the interior of the 22-kilometre-wide crater and extends to the rim of another crater on the horizon.

Opportunity has driven 41.7 kilometres since it landed in the Meridiani Planum region of Mars on January 25, 2004.

That is farther than any other off-Earth surface vehicle has driven. The rover's work on Mars was initially planned for three months.

"During that prime mission and for more than a decade of bonus performance in extended missions, Opportunity has returned compelling evidence about wet environments on ancient Mars," Nasa said.

Opportunity has been exploring Endeavour's western rim since 2011. From a low segment of the rim that it crossed in mid-2013, called "Botany Bay," it climbed about 135 meters in elevation to reach the top of Cape Tribulation.

The US flag is printed on the aluminium cable guard of the rover's rock abrasion tool, which is used for grinding away weathered rock surfaces to expose fresh interior material for examination.

"The flag is intended as a memorial to victims of the September 11, 2001, attacks on the World Trade Centre in New York. The aluminium was recovered from the site of the Twin Towers in the weeks following the attacks," Nasa said.