Polar Martian Dust Storm
A large dust storm was photographed erupting out from the north polar cap of Mars. Such dust storms are not uncommon as summer advances in the north. In the above picture taken by the Mars Global Surveyor spacecraft currently orbiting Mars, the white material is frozen carbon dioxide that covers much of the extreme north.
As the north polar cap region begins to thaw, a temperature difference occurs between the cold frost region and recently thawed surface, resulting in swirling winds between the adjacent regions.