Cassini at Saturn's moon Enceladus. Illustration of the Cassini spacecraft (left of centre) passing through the polar jets emitted from the surface of Saturn's moon Enceladus. Enceladus is one of the smaller moons of Saturn, with a diameter of around 505 kilometres. Plumes of water, hydrocarbons and other chemicals jet outwards from its surface. This surface is thought to be water ice over liquid water, a possible location for life in the Solar System outside Earth. Cassini flew through the plumes in October 2015. The Cassini spacecraft has been surveying the Saturnian system since 2004, with its mission scheduled to end in September 2017. This illustration is from the 'Cassini Grand Finale' film. Image published in 2017.