Orbiters around planets such as Mars have given us an unprecedented view of the whole surface, but sometimes you actually have to go down and have a look. Last week the Mars Polar Lander touched down and will be digging holes and studying the chemistry, but only in one place. Rovers like Spirit and Opportunity can travel further, but in over 4 years they have only travelled a few km which isn't far on a whole planet.
Researchers from Angstrom Aerospace in Sweden may have a solution to this problem. Their design involves putting the rover in what is basically a football. You put an axel across an inflatable sphere and then hang all the batteries and electronics below it, a bit like a pendulum. By moving this pendulum the robot can twist the axle and make the ball roll, and if it wants to steer it moves the pendulum to one or other side. The idea is to attach cameras and probes at the ends of the axle and if the robot wants to take a sample it can just tip over onto it's side.
The researches propose using these small robots as scouts for larger wheeled robots which would carry more sophisticated sensors