Geysers on Enceladus

This week’s image comes from Enceladus, an icy moon of Saturn. Credit goes to the Cassini team. The Cassini spacecraft orbits Saturn and performs frequent flybys of the various moons that orbit the gas giant.

This image shows plumes, or geysers erupting from the surface of the moon. They originate near the south pole of Enceladus and the material they eject seems to feed into Saturn’s ring system. These eruptions are very interesting as they are strong evidence for a process called Cryovolcanism. We usually think of volcanoes as being very hot, erupting molten rock in the form of Lava. On cold icy worlds like Enceladus similar processes are believed to occur. However the materials involved are very different.

 The term cryo comes from a greek word meaning “icy cold” and this is very apt when discussing the moons of Saturn. Instead of solid rock the surface of Enceladus is covered with ice. At the surface this doesn’t often thaw, as temperatures never get high enough. However it appears that the heat from the planets interior is sufficient to melt ice in the subsurface. This liquid water likely behaves much as magma does on Earth, including forming volcanoes in some areas. Cryolava erupts from the moon’s surface forming the geysers pictured here.

Cryovolcanism had been posited on a variety of cold planets and moons, including Europa, Titan and Pluto. However most of the evidence for cryovolcanism on these bodies came from the identification of features which appear similar to terrestrial volcanoes. Without studying them on the ground, or catching an eruption it is difficult to be certain whether they are really cryovolcanic features or not.  It wasn’t until 2005 that this image, and others from Enceladus caught a cryovolcanic process in the act. The existence of these plumes indicates that this moon is geologically active and provides strong evidence that cryovolcanism is possible across the colder regions of the solar system.