Mars rover counts to 100 and more

The rovers will spend 150 days longer on Mars than expected

The upload of new software to update both of the US space agency's Mars rovers has been completed successfully.

It took three days to send the files to Spirit and Opportunity, and all science activity with the buggies had to be suspended while the upgrades were done.

The new software should improve the vehicles' ability to drive greater distances each day through better autonomous navigation, the agency said.

Spirit, the first rover to land, has been on the planet for 100 Martian days

It has driven hundreds of metres away from its touchdown pad in Gusev Crater and is headed to elevated ground called Columbia Hills.

Opportunity, which landed on Meridiani Planum on the other side of the planet, is about 20 Martian days behind its twin in its mission.

Nasa recently funded an extension of the missions for both vehicles which will allow scientists to continue using the rovers to collect geological information about Mars right through September.

The new flight software upgrades should allow the buggies to complete that work without some of the glitches which have afflicted them in the early days on the planet.

Spirit suffered a flash memory overload and Opportunity has had a wayward thermostat on its robotic arm.

Nasa says the vehicles have been an astonishing success. Both have found evidence to show how water has influenced the rocks around their landing sites at some time in Mars' history.

Opportunity in particular has revealed remarkable information which suggests it came down on what was once the shoreline of a salty lake or sea.