What are cryovolcanoes?
Volcanism, as it is most commonly known, involves the eruption of hot, molten rock or ash. However, numerous worlds in our Solar System exhibit icy volcanism, or cryovolcanism, during which cryogenic mixtures – for example a briny slush, ammonia-water slurries or a mélange of icy particles and water vapour – are erupted instead of molten rock.
In addition to shaping the surfaces of several moons in the outer Solar System, cryovolcanism has also played a role in sculpting the surfaces of dwarf planets Ceres and Pluto. Just as Earth’s volcanoes are produced by the eruption and gradual build up of lava and ash, cryovolcanoes are produced in much the same way by the eruption of icy lava, or cryolava.
Dormant cryovolcanoes such as Ahuna Mons and Wright Mons have been imaged on Ceres and Pluto by NASA’s Dawn and New Horizons spacecraft respectively. A subset of domes on Jupiter’s moon Europa may also be small cryovolcanoes.
At present, active cryovolcanism in our Solar System takes the form of the eruption of geyserlike plumes on the moons of Jupiter, Saturn and Neptune. NASA’s Voyager 2 and Cassini spacecraft imaged geyser-like eruptions in the south polar regions of Neptune’s moon Triton and Saturn’s moon Enceladus respectively, while reanalysis of data from the Galileo spacecraft and observations by the Hubble Space Telescope and Keck Observatory reveal possible detections of geyser-like plumes on Jupiter’s moon Europa. In addition, Triton, Europa and Titan show evidence of recently emplaced cryolava flows, suggesting that cryovolcanism manifests in a variety of ways on their surfaces.