Galileo

Galileo orbited Jupiter for almost eight years, and made close passes by all its major moons. Its camera and nine other instruments sent back reports that allowed scientists to determine, among other things, that Jupiter’s icy moon Europa probably has a subsurface ocean with more water than the total amount found on Earth. They discovered that the volcanoes of the moon Io repeatedly and rapidly resurface the little world. They found that the giant moon Ganymede possesses its own magnetic field. Galileo even carried a small probe that it deployed and sent deep into the atmosphere of Jupiter, taking readings for almost an hour before the probe was crushed by overwhelming pressure.