Beneath Enceladus's south pole lies a watery ocean that could hold organic molecules that form the basis of life.

Luciano Iess at the Sapienza University of Rome and his colleagues analysed gravity measurements from the Cassini spacecraft during three flybys of this moon of Saturn in 2010–12. They found more mass than expected at the south pole, suggesting that something denser than ice was beneath the 30–40 kilometres of ice covering Enceladus's surface. The researchers think that a 10-km-thick layer of ocean covers the moon's rocky core.

In 2005, Cassini spotted water vapour and ice spraying through cracks in the icy shell near Enceladus's south pole. These jets could be carrying organic molecules and salts from this ocean to the surface, making the moon a place to search for possible extraterrestrial life.

Science 344, 78–80 (2014)