Cryovolcano

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Ganesa Macula, a dark feature on Saturn's moon Titan, might be a cryovolcanic dome.

A cryovolcano is, literally, an icy volcano. Cryovolcanoes form on icy moons, and possibly on other low-temperature astronomical objects (e.g. Kuiper belt objects). Rather than molten rock, these volcanoes erupt volatiles such as water, ammonia or methane. 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. Some scientists speculate that the cryovolcanoes on Titan, Saturn's largest moon, may harbor extraterrestrial life.

[edit] Theories

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.

It is hypothesised that the Kuiper belt object Quaoar has exhibited cryovolcanism in the past. In this case, the source of energy would be radioactive decay.

[edit] Observations

Cryovolcanoes are found on icy moons. Ice volcanoes were first observed on Neptune's moon Triton during the Voyager 2 flyby in 1989.

Plumes above the limb of Enceladus feeding Saturn's E Ring. These appear to emanate from the "tiger stripes" near the south pole.

The Cassini-Huygens mission has found a methane-spewing cryovolcano on Titan, and such volcanism is now believed to be a significant source of the methane found in Titan's atmosphere. On November 27, 2005 Cassini photographed geysers on the south pole of Enceladus (See also: Cryovolcanism on Enceladus).

Indirect evidence of cryovolcanic activity was later observed on several other icy moons of our solar system, including Europa, Ganymede, and Miranda.