Astonishing geology and the potential to host the conditions for simple life make Jupiter's moon Europa a fascinating destination for future exploration. Beneath its icy surface, Europa is believed to conceal a global ocean of salty liquid water twice the volume of Earth's oceans. Tugging and flexing from Jupiter's gravity generates enough heat to keep the ocean from freezing. On Earth, wherever we find water, we find life. What will NASA's Europa mission find when it heads for this intriguing moon in the 2020s.