Images sent back to Earth by the Mars Global Surveyor (Mgs) have given scientists a glimpse into the events that take place at the north pole when vast tracts of sand dunes become covered in frost.

Although it arrived at Mars in September 1997 it was only last summer that it was able to take images of the ring of sand dunes that circle the northern polar region.

When the image was finally taken last August, some keen-eyed scientists noticed that some of the dunes had dark streaks upon them.

White frost: Dark sand exposed by winds

Closer inspection revealed the Martian wind had blown away some of the frost exposing the dark sand beneath.

Because the frost is only as old as the Martian winter the wind erosion must have occurred within the past year or so.

These images, among the very best from Mgs's first year, will assist scientists to understand the strength of wind erosion on the surface.

Mars' north pole in 3D

Mars has winds that can attain high speeds but the atmosphere is so thin that even when the wind is blowing at its fiercest it would not blow you over.

At the moment it is springtime at the north pole of Mars. In a few weeks more powerful sunlight will fall on the frost covered dunes of dust that ring the pole and rid them of their frosty covering.

With luck the camera onboard the Mars Global Surveyor spacecraft will be watching.