A cryovolcano is a volcano that erupts volatile substances such as water, ammonia, methane, and brines instead of molten silicate rock. Cryovolcanism shapes the geology of many outer Solar System bodies, with confirmed activity on Enceladus and Triton and strong evidence on Europa, Ceres, and Pluto.
Last updated September 29, 2025
A cryovolcano is a volcanic system in which the erupted material is volatile-rich (for example, water, ammonia, methane, nitrogen, and saline brines) that would be solid at the ambient surface temperatures of icy worlds, rather than molten silicate rock typical of terrestrial volcanism USGS Publications Warehouse. Cryovolcanism is known or suspected on several outer Solar System bodies and arises where internal heat mobilizes such volatiles and delivers them to the surface through fractures and vents USGS Publications Warehouse.
Materials and physical properties
Cryovolcanic "magmas" (cryomagmas) may include mixtures of water with dissolved salts and ammonia, which depress freezing points and reduce viscosities, enabling flow at the low temperatures found on icy satellites and dwarf planets USGS Publications Warehouse. Laboratory and theoretical studies of the ammonia–water system show eutectic or near-eutectic melting transitions at temperatures around 176 K (pressure dependent), supporting the role of ammonia as an antifreeze in icy interiors NASA Technical Reports Server; ADS (J. Geophys. Res.). On Ceres, spectroscopic detections of sodium carbonate and ammonium salts within bright deposits indicate brine-derived residues, consistent with cryomagmatic transport and surface evaporation Nature; NASA.
Energy sources and eruption mechanisms
Internal heat that drives cryovolcanism may be supplied by tidal dissipation (notably for satellites of giant planets) or radiogenic heating and impact-related heat that can mobilize subsurface volatiles (especially for isolated dwarf planets) USGS Publications Warehouse. Tidal stressing can periodically open and close fractures, modulating venting, as inferred for Europa’s suspected plumes, which were detected when the moon was farthest from Jupiter and not seen near perijove NASA Science; Science. Modeling further suggests that shallow subsurface lakes within the ice shell can feed plumes or slushy cryolava flows, providing eruption sources separate from any deep global ocean NASA Europa Clipper. The compositions of cryomagmas, including salts and ammonia, can aid buoyancy and reduce the density contrast barrier that otherwise hinders ascent of liquid water through an ice shell USGS Publications Warehouse.
In 2005–2006, the Cassini mission discovered active plumes venting from fractures (“tiger stripes”) near the south pole of Enceladus, with infrared detections of a thermal anomaly indicating internal heat flow and ongoing endogenic activity Science; JPL. In situ dust and plasma measurements indicate that the plumes include salt-rich ice grains with “ocean-like” composition, implying interaction of liquid water with rock and consistent with a subsurface saltwater reservoir or ocean JPL; ESA. The total water vapor output has been estimated at roughly 200 kilograms per second, sustained over long periods and sufficient to supply material to Saturn’s E ring ESA; JPL.
During the 1989 flyby, Voyager 2 imaged geyser-like nitrogen plumes on Neptune’s moon Triton that rose to about 8 km and produced wind-blown streaks extending over 100 km, demonstrating active volatile-driven venting on an icy world Science; USGS. Proposed mechanisms include solar-heated nitrogen in a shallow subsurface greenhouse layer or explosive cryovolcanism; plume output rates inferred from imagery are of the same order as those measured for Enceladus, highlighting analogies in activity despite different primary volatiles USGS.
Ultraviolet observations by the Hubble Space Telescope in December 2012 yielded statistically significant excess emissions consistent with transient water vapor plumes up to ~200 km high over Europa’s south polar region, supporting the presence of intermittent venting Science; NASA Science. Subsequent Hubble imaging suggested recurring plumes at the same location and spatial coincidence with a thermal anomaly identified by the earlier Galileo mission, consistent with localized subsurface heat and active pathways through the ice shell JPL. Modeling indicates that shallow, wide liquid reservoirs within the shell could drive either vapor plumes or surface cryolava flows, a process testable by forthcoming Europa Clipper flybys NASA Europa Clipper.
Dawn mission data revealed Ahuna Mons as a prominent solitary dome interpreted as a cryovolcano formed by viscous extrusion of a saline, icy mixture in geologically recent times USGS Publications Warehouse; JPL. Within Occator Crater, bright deposits composed largely of sodium carbonate and ammonium salts record repeated ascent of brines through fractures, with some deposits retaining structural water that indicates very recent emplacement and possible ongoing activity; gravity and imaging analyses infer a deep brine reservoir roughly 40 km beneath the surface Nature; NASA. Topographic analyses suggest long-term, low-rate cryovolcanic resurfacing across Ceres, at average extrusion rates around 10^4 m^3 per year USGS Publications Warehouse.
Images and stereo topography from New Horizons revealed two large edifices—Wright Mons and Piccard Mons—with summit depressions, hummocky flanks, and geomorphology consistent with construction by repeated cryovolcanic eruptions of ices, making them leading candidates for large cryovolcanoes on Pluto JPL; NASA; JPL. These features imply internal heat and transport of volatiles late in Pluto’s geologic history, complementing evidence for widespread young terrains JPL.
Comparison with silicate volcanism
Cryovolcanic landforms can include domes, shields, caldera-like depressions (paterae), fissure-fed flows, and plume vents, paralleling many morphologies of silicate volcanism but constructed from low-temperature ices and brines that solidify quickly at the surface USGS Publications Warehouse. Unlike most silicate magma systems in which melts are buoyant relative to country rock, liquid water can be denser than its surrounding ice shell; dissolved salts and ammonia lower the density and melting point, aiding ascent, while tectonic fracturing and tidal flexure create conduits to the surface USGS Publications Warehouse; NASA Europa Clipper.
Planetary and astrobiological significance
Sustained venting supplies tenuous atmospheres and rings (for example, Enceladus feeds Saturn’s E ring), resurfaces terrain, and transports subsurface material to the exterior where it can be analyzed remotely or by spacecraft JPL; ESA. Because cryovolcanic plumes and flows can derive from reservoirs that interacted with rock, they provide access to ocean-derived chemistries of astrobiological interest on worlds such as Enceladus and Europa JPL; NASA Science.
Exploration and study
Evidence for cryovolcanism has been obtained by flyby and orbiter missions including Voyager 2 (Triton), Cassini–Huygens (Enceladus), Dawn (Ceres), and New Horizons (Pluto), as well as by Earth- and space-based telescopes such as Hubble for Europa USGS; Science; USGS Publications Warehouse; JPL; Science. Forthcoming dedicated investigations by Europa Clipper will probe the sources and dynamics of Europa’s activity and test models that link shallow reservoirs to plume and flow emplacement NASA Europa Clipper.
A cryovolcano is a volcano that erupts volatile substances such as water, ammonia, methane, and brines instead of molten silicate rock. Cryovolcanism shapes the geology of many outer Solar System bodies, with confirmed activity on Enceladus and Triton and strong evidence on Europa, Ceres, and Pluto.
Last updated September 29, 2025
A cryovolcano is a volcanic system in which the erupted material is volatile-rich (for example, water, ammonia, methane, nitrogen, and saline brines) that would be solid at the ambient surface temperatures of icy worlds, rather than molten silicate rock typical of terrestrial volcanism USGS Publications Warehouse. Cryovolcanism is known or suspected on several outer Solar System bodies and arises where internal heat mobilizes such volatiles and delivers them to the surface through fractures and vents USGS Publications Warehouse.
Materials and physical properties
Cryovolcanic "magmas" (cryomagmas) may include mixtures of water with dissolved salts and ammonia, which depress freezing points and reduce viscosities, enabling flow at the low temperatures found on icy satellites and dwarf planets USGS Publications Warehouse. Laboratory and theoretical studies of the ammonia–water system show eutectic or near-eutectic melting transitions at temperatures around 176 K (pressure dependent), supporting the role of ammonia as an antifreeze in icy interiors NASA Technical Reports Server; ADS (J. Geophys. Res.). On Ceres, spectroscopic detections of sodium carbonate and ammonium salts within bright deposits indicate brine-derived residues, consistent with cryomagmatic transport and surface evaporation Nature; NASA.
Energy sources and eruption mechanisms
Internal heat that drives cryovolcanism may be supplied by tidal dissipation (notably for satellites of giant planets) or radiogenic heating and impact-related heat that can mobilize subsurface volatiles (especially for isolated dwarf planets) USGS Publications Warehouse. Tidal stressing can periodically open and close fractures, modulating venting, as inferred for Europa’s suspected plumes, which were detected when the moon was farthest from Jupiter and not seen near perijove NASA Science; Science. Modeling further suggests that shallow subsurface lakes within the ice shell can feed plumes or slushy cryolava flows, providing eruption sources separate from any deep global ocean NASA Europa Clipper. The compositions of cryomagmas, including salts and ammonia, can aid buoyancy and reduce the density contrast barrier that otherwise hinders ascent of liquid water through an ice shell USGS Publications Warehouse.
In 2005–2006, the Cassini mission discovered active plumes venting from fractures (“tiger stripes”) near the south pole of Enceladus, with infrared detections of a thermal anomaly indicating internal heat flow and ongoing endogenic activity Science; JPL. In situ dust and plasma measurements indicate that the plumes include salt-rich ice grains with “ocean-like” composition, implying interaction of liquid water with rock and consistent with a subsurface saltwater reservoir or ocean JPL; ESA. The total water vapor output has been estimated at roughly 200 kilograms per second, sustained over long periods and sufficient to supply material to Saturn’s E ring ESA; JPL.
During the 1989 flyby, Voyager 2 imaged geyser-like nitrogen plumes on Neptune’s moon Triton that rose to about 8 km and produced wind-blown streaks extending over 100 km, demonstrating active volatile-driven venting on an icy world Science; USGS. Proposed mechanisms include solar-heated nitrogen in a shallow subsurface greenhouse layer or explosive cryovolcanism; plume output rates inferred from imagery are of the same order as those measured for Enceladus, highlighting analogies in activity despite different primary volatiles USGS.
Ultraviolet observations by the Hubble Space Telescope in December 2012 yielded statistically significant excess emissions consistent with transient water vapor plumes up to ~200 km high over Europa’s south polar region, supporting the presence of intermittent venting Science; NASA Science. Subsequent Hubble imaging suggested recurring plumes at the same location and spatial coincidence with a thermal anomaly identified by the earlier Galileo mission, consistent with localized subsurface heat and active pathways through the ice shell JPL. Modeling indicates that shallow, wide liquid reservoirs within the shell could drive either vapor plumes or surface cryolava flows, a process testable by forthcoming Europa Clipper flybys NASA Europa Clipper.
Dawn mission data revealed Ahuna Mons as a prominent solitary dome interpreted as a cryovolcano formed by viscous extrusion of a saline, icy mixture in geologically recent times USGS Publications Warehouse; JPL. Within Occator Crater, bright deposits composed largely of sodium carbonate and ammonium salts record repeated ascent of brines through fractures, with some deposits retaining structural water that indicates very recent emplacement and possible ongoing activity; gravity and imaging analyses infer a deep brine reservoir roughly 40 km beneath the surface Nature; NASA. Topographic analyses suggest long-term, low-rate cryovolcanic resurfacing across Ceres, at average extrusion rates around 10^4 m^3 per year USGS Publications Warehouse.
Images and stereo topography from New Horizons revealed two large edifices—Wright Mons and Piccard Mons—with summit depressions, hummocky flanks, and geomorphology consistent with construction by repeated cryovolcanic eruptions of ices, making them leading candidates for large cryovolcanoes on Pluto JPL; NASA; JPL. These features imply internal heat and transport of volatiles late in Pluto’s geologic history, complementing evidence for widespread young terrains JPL.
Comparison with silicate volcanism
Cryovolcanic landforms can include domes, shields, caldera-like depressions (paterae), fissure-fed flows, and plume vents, paralleling many morphologies of silicate volcanism but constructed from low-temperature ices and brines that solidify quickly at the surface USGS Publications Warehouse. Unlike most silicate magma systems in which melts are buoyant relative to country rock, liquid water can be denser than its surrounding ice shell; dissolved salts and ammonia lower the density and melting point, aiding ascent, while tectonic fracturing and tidal flexure create conduits to the surface USGS Publications Warehouse; NASA Europa Clipper.
Planetary and astrobiological significance
Sustained venting supplies tenuous atmospheres and rings (for example, Enceladus feeds Saturn’s E ring), resurfaces terrain, and transports subsurface material to the exterior where it can be analyzed remotely or by spacecraft JPL; ESA. Because cryovolcanic plumes and flows can derive from reservoirs that interacted with rock, they provide access to ocean-derived chemistries of astrobiological interest on worlds such as Enceladus and Europa JPL; NASA Science.
Exploration and study
Evidence for cryovolcanism has been obtained by flyby and orbiter missions including Voyager 2 (Triton), Cassini–Huygens (Enceladus), Dawn (Ceres), and New Horizons (Pluto), as well as by Earth- and space-based telescopes such as Hubble for Europa USGS; Science; USGS Publications Warehouse; JPL; Science. Forthcoming dedicated investigations by Europa Clipper will probe the sources and dynamics of Europa’s activity and test models that link shallow reservoirs to plume and flow emplacement NASA Europa Clipper.
