The US space agency's (Nasa) Mars rovers are celebrating a remarkable five years on the Red Planet.

The first robot, named Spirit, landed on the 3^rd of January 2004, 21 days later followed by its twin, Opportunity. After being expected to work only for at least three months, the six-wheel robotic geologists are still on the job, overcoming everyone’s expectations by their longevity in the freezing Martian conditions.

 

NASA said the rovers had made important discoveries about the wet and violent conditions on ancient Mars.

 

Spirit has begun stirring after sitting immobile for most of the autumn and winter, JPL spokesman Guy Webster said Saturday. Plans are being made to have it explore a 150km-wide bowl-shaped depression known as Gusev Crater. It has found an abundance of rocks and soils bearing evidence of extensive exposure to water.

 

Opportunity, which is closer to the equator in a flat region known as Meridiani Planum has cleaner solar panels and has been driving toward a 14-mile-diameter crater, stopping on the way to examine interesting rocks. Its data has shown conclusively that Mars sustained liquid water on its surface. The sedimentary rocks at its study location were covered by gently flowing surface water.

 

Combined, the rovers have made more than 21 kilometers (13 miles) of tracks on Mars' dusty surface and sent 250,000 images back to Earth, climbed a mountain, descended into craters, struggled with sand traps and ageing hardware and survived dust storms. They have provided evidence that Mars was billions of years ago a far wetter and warmer place than the frigid, dusty world it is now.

 

The rovers are now showing some serious signs of wear and tear.

 

When Spirit and Opportunity do eventually fail, Nasa will have to wait awhile for its next surface mission.