A mission to explore Phobos, one of the two moons circling Mars, has been proposed that would release spherical spiky satellites, referred to as hedgehogs, say scientists from Stanford, NASA and MIT. The mission would have two stages. In the first, a surveyor satellite would travel to Phobos, then it will release the spherical robots.
Because the gravity on the moon is weaker than Mars, it would be difficult for a rover like Curiosity to get traction. However spherical robots with spikes would be able to hop and bounce over the terrain safely. The hedgehogs, about half a meter across, will move by three rotating discs on their interiors. This will enable them to move and explore the surface.