Fountains of water ice blast thousands of kilometres above the surface of Saturn's tiny moon Enceladus. It is thought that the pull of Saturn's powerful gravity distorts the moon and heats the interior, forming an underground ocean. When this reservoir of water contacts the vacuum of space it vaporises and explodes above the moon. Any liquid water freezes instantly.
Images of the ice fountains were first captured by the Cassini probe.
Photo: Immense ice geysers are revealed when Enceladus is backlit by the Sun (NASA/JPL/Space Science Institute)
Jets of ice blast high above Saturn's moon.
Enceladus is a curious moon with tiger stripes and ice fountains.
Professor Brian Cox meets Professor Carolyn Porco to find out what the Cassini spacecraft discovered about Saturn's curious moon Enceladus.
Spectacular ice fountains on one of Saturn's moons blast up into space.
Professor Brian Cox explores geysers in Iceland and discovers how the ice fountains on Saturn's moon Enceladus get their power.
A cryovolcano (colloquially known as an ice volcano) is a volcano that erupts volatiles such as water, ammonia or methane, instead of molten rock. Collectively referred to as cryomagma or ice-volcanic melt, these substances are usually liquids and form plumes, but can also be in vapour form. After eruption, cryomagma condenses to a solid form when exposed to the very low surrounding temperature. Cryovolcanoes form on icy moons, and possibly on other low-temperature astronomical objects (e.g., Kuiper belt objects).
The energy required to melt ices and produce cryovolcanoes usually comes from tidal friction. It has also been suggested that translucent deposits of frozen materials could create a sub-surface greenhouse effect that would accumulate the required heat.
Signs of past warming of the Kuiper belt object Quaoar have led scientists to speculate that it exhibited cryovolcanism in the past. Radioactive decay could provide the energy necessary for such activity, as cryovolcanoes can emit water mixed with ammonia, which would melt at 180 K (−95 °C) and create an extremely cold liquid that would flow out of the volcano.