The geysers of Enceladus

Enceladus is only about 500 kilometers across and seemed too small to have any internal activity. In 2005, the Cassini probe changed that view by catching jets of water vapor and ice particles shooting out of fissures at the moon's south pole, nicknamed tiger stripes. Some of that material feeds one of Saturn's rings.

Cassini flew through the plumes several times and analyzed what was in them. It found salt, organic molecules and hydrogen, a sign of reactions between water and rock at the bottom of a global ocean hidden under the ice, possibly at hydrothermal vents similar to those in Earth's oceans. Later studies of the data also identified phosphates. Enceladus brings together almost everything life as we know it needs, which places it among the most studied places in this search.