Scientists from the American space agency, NASA, say new satellite pictures of Mars reveal that its north pole has an ice cap wider than France but much smaller than previously thought.

The new data -- from the space probe, Mars Global Explorer -- also shows the region may contain much less water than scientists originally believed.

Researchers say in some areas, the surface is riddled with canyons -- one trough is deeper than the Grand Canyon in the United States.

Our Science Correspondent says geologists will now have to rethink the history of the planet, to include the fact that any water on its surface would have tended to flow towards the poles rather than away from them.