• Volcanoes on Earth are associated with eruptions of fiery rock, ash, and gases. However, another type of volcano exists in the universeice volcanoes.

    Dr. Rosaly Lopes, a senior research scientist at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, says cryovolcanoes, or ice volcanoes, are found on Enceladus, a moon of Saturn. Lopes and other scientists hypothesize that cryovolcanoes also exist on Triton, a moon of Neptune, and Titan, another moon of Saturn.

    Lopes has studied volcanoes on Earth, which spew hot, molten rock known as lava. Cryovolcanoes erupt with different materials. “These satellites have ice crusts,” she says. “And under the ice crusts, there is a layer of water, or perhaps water with something else like ammonia, and if that liquid can come to the surface, that is what we call cryovolcanism. It just means cold volcanism.”

    Though the material erupting from a cryovolcano is different from that of a terrestrial volcano, the action that causes the eruption is comparable, she says.

    “We call it volcanism because it’s a process that brings material from the interior of the satellite to the surface,” Lopes says. “So that is similar to volcanism as we see on other planets, but the material itself is quite different. It’s an aqueous mixture rather than molten rock.”

    According to Lopes, there are two necessary ingredients for cryovolcanism: “You need a heat in the interior and a liquid under the surface that can become buoyant.”

    Lopes says the best examples of cryovolcanism are on Saturn’s moon Enceladus. When NASA’s Cassini spacecraft flew by Enceladus in 2005, it took images of at least 20 icy plumes spewing a mixture of ice particles, water vapor, and other materials into space.

    Dr. Randy Kirk, a geophysicist at the U.S. Geological Survey’s Astrogeology Science Center in Flagstaff, Arizona, compares the icy plumes to a phenomenon that occurs here on Earth. “It’s like a geyser that reaches escape velocity and blasts the steam into space,” he says.

    Kirk and Lopes note that there is evidence of past cryovolcanism on Triton, the largest of Neptune’s 13 moons. NASA’s Voyager 2 spacecraft helped scientists observe that Triton’s surface is composed of smooth plains, mounds, and rock pits. Many scientists hypothesize that the landscape was created in part by a cryovolcano’s icy flows.


    Recently, Lopes and Kirk have turned their attention to Titan, the largest of 62 known moons orbiting Saturn. After Kirk constructed a 3-D model of an area on Titan known as Sotra Facula, Lopes began thinking the moon might be home to cryovolcanoes.

    “It became apparent that the feature [Sotra Facula] looked volcanic,” Lopes says. “There was a tall mountain and a crater next to it like a pit. There were flows. Our best interpretation is that it’s a cryovolcanic region.”

    The existence of cryovolcanism on Titan is still debated in the scientific community. Lopes admits scientists have yet to see evidence of significant heat—a necessary part of cryovolcanism—on the moon.

    “What would excite me the most would be if we actually saw a thermal signal that indicated active cryovolcanism or some other surface change that really could confirm the idea that volcanism on Titan is still taking place,” she says.

    If cryovolcanism were occurring on Titan, it would make the moon a more interesting place for scientists. “The question is whether Titan is dead or alive,” Lopes says. “Is it a world that’s still changing from its interior, or has it stopped doing anything a long time ago and now the surface just sits there being modified by what we call exogenic processes, which are processes that are external, like erosion and impact cratering.”

    Kirk says that if the interior of Titan is composed of methane, cryovolcanism could help account for why the gas is so present in the moon’s atmosphere.

    “It would be a puzzle piece that would help explain why we see a methane-rich atmosphere on Titan,” he says.

    The confirmed existence of cryovolcanism on Titan could lead to an even greater discovery.

    “If it had volcanism in the past or it still has any activity, you open up the possibility for some very interesting chemistry if you have heat and you have water,” Lopes says. “Then there is the possibility of life.”

    Cold Explosion
    Sotra Facula is a region on Titan, Saturn's largest moon. Sotra Facula may be a cryovolcano with two peaks, each more than 1,000 meters (3,300 feet) high.

    World Record Holder
    From 1996 to 2001, Dr. Rosaly Lopes worked for NASAs Galileo mission, analyzing data on Jupiters moon Io. I actually was very thrilled to discover . . . 71 volcanoes on Io that had not previously been known, she says. I ended up in the Guinness Book of World Records in 2006 for having discovered the largest number of volcanoes anywhere.

    Icy Eruption
    The material spewed from a cryovolcano on Enceladus, a moon of Saturn, would have a temperature of -3 C to -116 C (27 F to -177 F, or 270 to 157 Kelvin).

  • Term Part of Speech Definition Encyclopedic Entry
    3-D map Noun

    representation of spatial information using dimensions of depth, length, and width.

    ammonia Noun

    a gas (NH3) important to food production.

    aqueous Adjective

    containing water or a substance similar to water.

    astrogeology Noun

    study of the physical history and structure of planets and moons.

    atmosphere Noun

    layers of gases surrounding a planet or other celestial body.

    Encyclopedic Entry: atmosphere
    buoyant Adjective

    capable of floating.

    Cassini-Huygens Noun

    mission to study the planet Saturn and its moons.

    chemistry Noun

    study of the atoms and molecules that make up different substances.

    confirmation Noun

    assurance that something is true.

    crater Noun

    bowl-shaped depression formed by a volcanic eruption or impact of a meteorite.

    Encyclopedic Entry: crater
    crust Noun

    rocky outermost layer of Earth or other planet.

    Encyclopedic Entry: crust
    cryovolcano Noun

    volcano that erupts with ice, water, and other materials (such as methane and ammonia), instead of molten rock and ash. Also called an ice volcano.

    Earth Noun

    our planet, the third from the Sun. The Earth is the only place in the known universe that supports life.

    Encyclopedic Entry: Earth
    erosion Noun

    act in which earth is worn away, often by water, wind, or ice.

    Encyclopedic Entry: erosion
    eruption Noun

    release of material from an opening in the Earth's crust.

    escape velocity Noun

    speed and force that an object must have to escape the gravity of a larger body, instead of orbiting around it.

    exogenic Adjective

    external, or coming from outside the thing being affected.

    gas Noun

    state of matter with no fixed shape that will fill any container uniformly. Gas molecules are in constant, random motion.

    geyser Noun

    natural hot spring that sometimes erupts with water or steam.

    Encyclopedic Entry: geyser
    hypothesis Noun

    statement or suggestion that explains certain questions about certain facts. A hypothesis is tested to determine if it is accurate.

    hypothesize Verb

    to form a statement or suggestion that explains certain questions about certain facts.

    ice Noun

    water in its solid form.

    Encyclopedic Entry: ice
    impact crater Noun

    circular surface depression made by the impact of a meteorite.

    indicate Verb

    to display or show.

    Jet Propulsion Laboratory (JPL) Noun

    NASA center that focuses on robotic exploration of the solar system.

    landscape Noun

    the geographic features of a region.

    Encyclopedic Entry: landscape
    lava Noun

    molten rock, or magma, that erupts from volcanoes or fissures in the Earth's surface.

    methane Noun

    chemical compound that is the basic ingredient of natural gas.

    model Noun

    image or impression of an object used to represent the object or system.

    molten Adjective

    solid material turned to liquid by heat.

    moon Noun

    natural satellite of a planet.

    Encyclopedic Entry: moon
    NASA Noun

    (National Aeronautics and Space Administration) the U.S. space agency, whose mission statement is "To reach for new heights and reveal the unknown so that what we do and learn will benefit all humankind."

    Neptune Noun

    eighth planet from the sun in our solar system.

    orbit Verb

    to move in a circular pattern around a more massive object.

    Encyclopedic Entry: orbit
    phenomenon Noun

    an unusual act or occurrence.

    plain Noun

    flat, smooth area at a low elevation.

    Encyclopedic Entry: plain
    planet Noun

    large, spherical celestial body that regularly rotates around a star.

    Encyclopedic Entry: planet
    plume Noun

    single, upward flow of a fluid, such as water or smoke.

    satellite Noun

    object that orbits around something else. Satellites can be natural, like moons, or made by people.

    Saturn Noun

    sixth planet from the sun.

    scientist Noun

    person who studies a specific type of knowledge using the scientific method.

    spacecraft Noun

    vehicle designed for travel outside Earth's atmosphere.

    steam Noun

    water vapor.

    terrestrial Adjective

    having to do with the Earth or dry land.

    Titan Noun

    largest moon of the planet Saturn.

    universe Noun

    all known matter, energy, and space.

    vapor Noun

    visible liquid suspended in the air, such as fog.

    volcanic ash Noun

    fragments of lava less than 2 millimeters across.

    Encyclopedic Entry: Human and Environmental Impacts of Volcanic Ash
    volcano Noun

    an opening in the Earth's crust, through which lava, ash, and gases erupt, and also the cone built by eruptions.

    Encyclopedic Entry: Plate Tectonics and Volcanic Activity