Cryovolcanism in the Solar System

Planetary volcanism is manifested across a range of morphologies, driving conditions, and compositions, including ices. Volcanism that occurs on the outer solar system's satellites, known as cryovolcanism [1], is primarily the eruption of aqueous or non-polar molecular solutions or partly crystallized slurries, derived from partial melting of ice-bearing materials. Neptune's moon Triton was the first object where active plumes were observed by Voyager 2 in 1989, interpreted as possibly cryovolcanic. Galileo observations showed evidence of cryovolcanism on Europa and Ganymede and later observations by HST have detected possible water vapor plumes from Europa. The New Horizons spacecraft identified features on Pluto and Charon interpreted as cryovolcanic while, in the inner solar system, the Dawn spacecraft imaged a possible cryovolcanic mountain on Ceres, providing further evidence of the importance of cryovolcanism in shaping planetary surfaces. The Cassini mission to Saturn and its moons has significantly added to our knowledge of cryovolcanism, revealing active jets from Enceladus that bring material from a global interior ocean. Cryovolcanism likely also occurred on Titan, a world that Cassini data have revealed to be complex, in which interior, surface and atmospheric processes interact to create and modify geologic features. Spacecraft data have revealed evidence of global oceans beneath the icy shells of a variety of icy bodies. In some cases, these subsurface oceans could supply the requisite protection, key elements, and energy sources to provide habitable conditions for, and facilitate the development of, simple lifeforms on these ocean worlds. Communication between the ocean and the surface in the form of cryovolcanism might therefore provide an essential pathway for biosignatures originating in the ocean to be delivered to the surface where they could be detected by spacecraft instruments searching for signs of extraterrestrial life. This paper will review the range of cryovolcanic features that have been observed on icy bodies and what we know about their origin. [1] Fagents, S.A., et al. Cryovolcanism. In: Planetary Volcanism across the Solar System. https://doi.org/10.1016/B978-0-12-813987-5.00005-5