Mars has been hurtling towards the Earth at almost 50,000kmh - a million kilometres each day.

It reached its closest point on 1 May, and will soon start to move away again at the same speed.

Mars pictured from Mars Global Surveyor

It will be another two years before Mars comes as close again.

Although popularly called the red planet, Mars appears as a bright yellow star in the night sky - the colour coming from the sun reflecting off its yellow, dusty deserts.

Interest in Mars has intensified in recent years as evidence has grown that life might once have existed on its surface.

The Mars Global Surveyor, an unmanned spacecraft, is currently mapping the planet, and three more unmanned missions are on their way.

Similarities to earth?

Fido, a new robot explorer, is tested in California

On Thursday, scientists suggested that Mars had once been subject to a process of plate tectonics, similar to the process which continues to shape the continents on earth.

They reached their conclusions on the basis of information gathered by the Mars Global Surveyor, which pointed to the presence of patches of magnetised material on the surface of Mars.

These magnetised patches suggest the movement of plates that make up the planet's surface, according to John Connerney, a researcher based at Nasa's Goddard Space Flight Centre.

While this process continues on earth, indications are that tectonic activity on Mars has come to an end.