Beneath the cold icy surface of Jupiter's moon Europa are probably the only oceans of water in our Solar System outside of Earth. These oceans, possibly 50 kilometers deep, might also be the most likely local place to find extra-terrestrial life. Europa's smooth surface is unlike any other known planet or moon, giving evidence for relatively few craters or mountains. Europa was discovered by Galileo and Marius in 1610. The NASA spacecraft Galileo is scheduled to arrive at Jupiter in December of 1995.