Out of this world: earth seen from Mars

It's a unique view of our world: a pale blue disc, half in shadow, with the moon seemingly just a short distance away. The bright patch at the top of the disc is cloud swirling over North America. Further down to the right, clouds build over South America.

The image is a first, the view of Earth and its natural satellite snapped from Mars at a distance of 86m miles. It was taken by the Mars Global Surveyor, a Nasa probe that has been orbiting the red planet since September 1997, using cameras and magnetic sensors to map the surface.

One of its tasks has been to check the landing sites for Nasa's two Mars Exploration Rovers and Beagle 2, Britain's first mission to Mars, which launches from Kazakhstan on June 2.

Colin Pillinger's Beagle 2 probe is due to land on Mars early on Christmas Day. "As we leave, now is a great time to be thinking about what we leave behind," said Professor Pillinger, of the Open University in Milton Keynes.

"We've spent the last six-and-a-half years staring at Mars right in front of us," said Michael Malin, head of Malin Space Science Systems in San Diego, California, which operates the probe's camera. "This image gives us a new perspective on that neighbourhood, one in which we can see our own planet as one of many."

In 2001 the Mars Global Surveyor found evidence that the red planet was enduring a period of intense global warming: permafrost at its southern pole had shrunk significantly in two successive years.