A close-up of the ice-rafts on Europa

The ridges are caused when the surface ice fractures and pulls apart. Fresh ice forms in the fracture zone resulting in linear ridges that can stretch for thousands of kilometres across the surface.

Europa is the smoothest world in the solar system. Nothing is higher than 200 metres.

Ice domes a few kilometres in size and smaller ridges can be seen on the surface as well as discoloration in the ice caused when material was dredged up from beneath the ice following an impact with an asteroid.

Europa has become one of the most important bodies to study in our solar system. Some scientists believe that beneath its icy crust there may be an ocean of water.

Heated from below by hot rocks, the sub-ice ocean may be suitable for primitive life to develop.

To take a closer look at Europa scientists are designing a Europa orbiter spacecraft that they hope will be launched towards the icy moon in the early years of the next century.