Mars has a long history of liquid water on its surface, although the surface today is mostly dry and cold. However, there is strong evidence for subsurface water on Mars, and even today water flows briefly on the surface under the right conditions. Enceladus may have the most accessible liquid water, which is squirting into space by means of the geysers observed with our Cassini spacecraft. Titan is in many ways the most interesting world we have explored. It is far too cold for liquid water, but with its thick atmosphere and hydrocarbon lakes, it may be the best place to search for “life as we don’t know it.” We now come to the end of our study of the planetary system. Although we have learned a great deal about the other planets during the past few decades of spacecraft exploration, much remains unknown. Discoveries in recent years of geological activity on Titan and Enceladus were unexpected, as was the complex surface of Pluto revealed by New Horizons. The study of exoplanetary systems provides a new perspective, teaching us that there is much more variety among planetary systems than scientists had imagined a few decades ago.

Volcanism on Io Io, with two plumes erupting from its surface, Galileo image, June 1997 Io, a moon of Jupiter, has a substantial presence of volcanoes, volcanic pits and lava flows on its surface. Volcanic activity on the moon was first discovered in 1979 by Linda Morabito, an imaging scientist working on Voyager 1. Observations of Io by passing spacecraft and Earth-based astronomers have revealed more than 150 active volcanoes. As of 2024, up to 400 such volcanoes are predicted to exist based on these observations. Io's volcanism makes the satellite one of only five known currently volcanically or cryovolcanically active worlds in the Solar System (the others being Earth, Venus, Saturn's moon Enceladus, and Neptune's moon Triton.) First predicted shortly before the Voyager 1 flyby, the heat source for Io's volcanism comes from tidal heating produced by its forced orbital eccentricity. This differs from Earth's internal heating, which is derived primarily from radioactive isotope decay and primordial heat of accretion. Io's eccentric orbit leads to a slight difference in Jupiter's gravitational pull on the satellite between its closest and farthest points on its orbit, causing a

Cryovolcanism in the outer solar system USGS Publications Warehouse ### Cryovolcanism in the outer solar system By: Metrics Web analytics dashboard Metrics definitions #### Links - Disclaimer - The Publications Warehouse does not have links to digital versions of this publication at this time - Download citation as: RIS| Dublin Core #### Abstract Cryovolcanism is defined as the extrusion of liquids and vapors of materials that would be frozen solid at the planetary surface temperatures of the icy bodies of the outer solar system. Active cryovolcanism is now known to occur on Saturn's moon Enceladus and on Neptune's moon Triton and is suspected on Jupiter's moon Europa, while evidence for past cryovolcanic activity is widespread throughout the outer solar system. This chapter examines the mechanisms and manifestations of cryovolcanism, beginning with a review of the materials that make up these unusual ‘‘magmas’’ and the means by which they might erupt and concluding with a volcanologist's tour of the farthest reaches of the solar system. #### Suggested Citation Geissler, P.E., 2015, Cryovolcanism in the outer solar system, chap. of The encyclopedia of volcanoes, p. 763-77

Cryovolcanism in the outer solar system | U.S. Geological Survey Skip to main content # Cryovolcanism in the outer solar system Cryovolcanism is defined as the extrusion of liquids and vapors of materials that would be frozen solid at the planetary surface temperatures of the icy bodies of the outer solar system. Active cryovolcanism is now known to occur on Saturn's moon Enceladus and on Neptune's moon Triton and is suspected on Jupiter's moon Europa, while evidence for past cryovolcanic activity is widespread throughout the outer solar system. This chapter examines the mechanisms and manifestations of cryovolcanism, beginning with a review of the materials that make up these unusual ‘‘magmas’’ and the means by which they might erupt and concluding with a volcanologist's tour of the farthest reaches of the solar system. ## Citation Information | Publication Year | 2015 | | --- | --- | | Title | Cryovolcanism in the outer solar system | | Authors | Paul E. Geissler | | Publication Type | Book Chapter | | Publication Subtype | Book Chapter | | Index ID | 70168446 | | Record Source | USGS Publications Warehouse | | USGS Organization | Astrogeology Science Center | Was this page

## Chapter 5 Cryovolcanism Sarah A. Fagents Hawaiʻi Institute of Geophysics and Planetology, University of Hawaiʻi at Mānoa, Honolulu, HI 96825; fagents@hawaii.edu Rosaly M.C. Lopes Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109; rosaly.m.lopes@jpl.caltech.edu Lynnae C. Quick NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771; Lynnae.C.Quick@nasa.gov Tracy K.P. Gregg Department of Geology, University at Buffalo, Buffalo, NY 14260 Abstract Cryovolcanism has been observed in several bodies in the solar system, most notably Saturn’s moon Enceladus, where jets of water vapor and other constituents are spewed into space. Here we review cryomagmatism and cryovolcanism, which are the subsurface and surface processes resulting from the mobilization and migration of fluids generated in the interiors of icy bodies. While these have no counterparts on Earth, they are important processes in the Solar System, particularly in the icy moons of the outer Solar System. We discuss mechanisms of cryomagmatism and cryovolcanism, the possible compositions of cryomagmas, and the observational evidence found so