Data sent from the Galileo spaceprobe indicates that Jupiter's moon Europa has a liquid ocean under a thick crust of ice.
If size did matter, the dinosaurs would still be alive.
Luna program: The Soviet Union lands Lunokhod 1 on Mare Imbrium (Sea of Rains) on the Moon. This is the first roving remote-controlled robot to land on another world and was released by the orbiting Luna 17 spacecraft.
