Saturn's moon Enceladus. Computer artwork of a view across Enceladus towards Saturn in the sky above. Enceladus is the sixth-largest moon of Saturn. It measures 500 kilometres in diameter and is a frozen world with a surface consisting mostly of water ice. Like all of Saturn's major satellites, Enceladus always keeps the same side facing its host planet. This image also illustrates a recently discovered phenomenon: sunlight reflecting off Saturn's rings casts a faint glow onto the cloud tops of Saturn's night side.