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.

Titan

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.

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).

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.

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.

Noun

layers of gases surrounding a planet or other celestial body.

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.

Noun

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

Noun

rocky outermost layer of Earth or other planet.

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.

Noun

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

Noun

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

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.

Noun

natural hot spring that sometimes erupts with water or steam.

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.

Noun

water in its solid form.

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.

Noun

the geographic features of a region.

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.

Noun

natural satellite of a planet.

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.

Verb

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

phenomenon
Noun

an unusual act or occurrence.

Noun

flat, smooth area at a low elevation.

Noun

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

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.

Noun

fragments of lava less than 2 millimeters across.

Noun

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