||This article needs attention from an expert in Volcanoes or Solar System. (February 2008)|
A cryovolcano (colloquially known as an ice volcano) is a theoretical type of 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 can form plumes, but can also be in vapour form. After eruption, cryomagma is expected to condense to a solid form when exposed to the very low surrounding temperature. Cryovolcanoes may potentially form on icy moons and other objects with abundant water past the Solar System's snow line (such as Pluto). A number of features have been identified as possible cryovolcanoes on Pluto, Titan and Ceres. In addition, although they are not known to form volcanoes, ice geysers have been observed on Enceladus and potentially Triton.
One potential energy source on some solar system bodies for melting ices and producing cryovolcanoes is tidal friction. It has also been suggested[by whom?] that translucent deposits of frozen materials could create a subsurface 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.
Indirect evidence of cryovolcanic activity was later observed on several other icy moons of the Solar System, including Europa, Titan, Ganymede, and Miranda. Cassini has observed several features thought to be cryovolcanoes on Titan, notably Doom Mons with adjacent Sotra Patera, a feature regarded as "the very best evidence, by far, for volcanic topography anywhere documented on an icy satellite". Cryovolcanism is one process hypothesized to be a significant source of the methane found in Titan's atmosphere.
In 2007, observations by the Gemini Observatory showing patches of ammonia hydrates and water crystals on the surface of Pluto's moon Charon suggested the presence of active cryovolcanoes or cryogeysers. Subsequent observations by New Horizons in 2015 found that Charon has a youthful surface, supporting this idea. Pluto itself has two features that have been identified as possible cryovolcanoes, being mountains with indented peaks.
In September 2016, NASA JPL and NASA Goddard scientists released findings that large Ahuna Dome on Ceres is a "volcanic dome unlike any seen elsewhere in the solar system. [The large] mountain is likely volcanic in nature. Specifically, it would be a cryovolcano -- a volcano that erupts a liquid made of volatiles such as water, instead of silicates. ... the only known example of a cryovolcano that potentially formed from a salty mud mix, and that formed in the geologically recent past." In addition, at least some of Ceres' well known bright spots (notably including the ones in Occator crater) are likely also cryovolcanic in origin. A study published in March 2017 suggests that Occator's most recent large eruption occurred about 4 million years ago and thus that Ceres may still be active. 
|Cryovolcanism on Enceladus|
- Lopes, R. M. C.; Kirk, R. L.; Mitchell, K. L.; et al. (2013). "Cryovolcanism on Titan: New results from Cassini RADAR and VIMS". Journal of Geophysical Research: Planets. 118 (3): 416–435. Bibcode:2013JGRE..118..416L. doi:10.1002/jgre.20062.
- Darling, David (ed.). "Cryovolcanism". Internet Encyclopedia of Science.
- Witze, Alexandra. "Ice volcanoes may dot Pluto's surface". Nature.
- Jewitt, D.C.; J. Luu (2004). "Crystalline water ice on the Kuiper belt object (50000) Quaoar". Nature. 432 (7018): 731–3. Bibcode:2004Natur.432..731J. doi:10.1038/nature03111. PMID 15592406.. Reprint on Jewitt's site (pdf)
- Chang, Kenneth (March 12, 2015). "Suddenly, It Seems, Water Is Everywhere in Solar System". New York Times. Retrieved March 12, 2015.
- "Cassini Spots Potential Ice Volcano on Saturn Moon". NASA, December 14, 2010
- Media Relations Office: Cassini Imaging Central Laboratory For Operations (2009). "Cassini Finds Hydrocarbon Rains May Fill The Lakes". Space Science Institute, Boulder, Colorado. Retrieved 4 March 2015.
- "Charon: An ice machine in the ultimate deep freeze". Gemini Observatory. 2007. Retrieved 18 July 2007.
- Cook; Desch, Steven J.; Roush, Ted L.; Trujillo, Chadwick A.; Geballe, T. R.; et al. (2007). "Near-Infrared Spectroscopy of Charon: Possible Evidence for Cryovolcanism on Kuiper Belt Objects". The Astrophysical Journal. 663 (2): 1406–1419. Bibcode:2007ApJ...663.1406C. doi:10.1086/518222.
- Beatty, Kelly (2 October 2015). "Charon: Cracked, Cratered, and Colorful". Sky and Telescope. Retrieved 2015-10-03.
- Witze, A. (2015-11-09). "Icy volcanoes may dot Pluto's surface". Nature News and Comment. Nature Publishing Group. doi:10.1038/nature.2015.18756. Retrieved 2015-11-09.
- O'Neill, I. (25 February 2015). "Ceres' Mystery Bright Dots May Have Volcanic Origin". Discovery Communications. Retrieved 1 March 2015.
- Triton - Triton at the eight Planets
- South Pole of Triton - Triton at SolarViews.com
- Enceladus' South Polar Stripes Spew "Warm" Water - News article at the Planetary Society
- Cryovolcanism on Charon and other Kuiper Belt Objects
- Ice Volcanoes of Lake Superior's South Shore
- Dykes, Brett Michael (February 8, 2011). "Ice volcanoes are all the rage this winter: How do you stimulate a regional tourist economy?". The Lookout. Yahoo News. Retrieved February 8, 2011.
- Herzog, Karen (February 6, 2011). "Ice volcanoes attract curious explorers to Lake Michigan shore: Experts warn to explore formations with caution". Journal Sentinel. Retrieved February 8, 2011.