The Copernican revolution began over 500 years ago with the realization that the Earth was not the centre of the universe, but we still await its grand finale: the anticipated discovery of life elsewhere. Where else might we find life? The vast scale of the universe makes it virtually certain that there are other Earth- like settings. In our own solar system, Mars’s distance from the Sun makes it sufficiently Earth-like; so, especially with increasing evidence for occasional liquid water, many are looking there for the first signs of extraterrestrial life. Recently, however, a new contender has emerged, and surprisingly it is from the cold outer solar system: it is Jupiter’s moon Europa. As one of the four satellites of Jupiter, discovered by Galileo in 1610, Europa is now believed to have water in a liquid state, even though it is so far from the Sun. Thus, the possibility of liquid water on Europa has opened the door to speculation about life on this satellite of Jupiter.