Saturn's Moon Throws Fountains of Water Into Space

PASADENA, California, March 12, 2006 (ENS) - One of Saturn's moons is sending geysers of water into space that fall back to the moon as snow, a joint U.S.-European exploratory space mission reports. The plumes of icy water also replenish the water particles that make up Saturn's largest ring - the E-ring, the scientists have discovered.

Data from the spacecraft Cassini obtained during a close flyby of Saturn's moon Enceladus show that large amounts of water are spewing into space from the tiny moon's surface. This water originates near "south polar hot spots on the moon, possible locations for the development of primitive life in the solar system," the scientists said.

"We realize that this is a radical conclusion - that we may have evidence for liquid water within a body so small and so cold," said Dr. Carolyn Porco, Cassini imaging team leader at Space Science Institute, Boulder, Colorado. "However, if we are right, we have significantly broadened the diversity of solar system environments where we might possibly have conditions suitable for living organisms."


Cassini images of Saturn's moon Enceladus backlit by the Sun show the fine spray of material that towers over the south polar region. This enhanced and colorized image shows discrete plumes of a variety of sizes. (Photo courtesy NASA/JPL/Space Science Institute)
The Cassini spacecraft is the first spacecraft to explore the Saturn system of rings and moons from orbit. Launched in October 1997, Cassini entered Saturn's orbit on July 1, 2004 and immediately began sending back images and data.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder.

Saturn's moon Enceladus is the source of Saturn's E-ring, confirms research published Friday. The E-ring is Saturn's outermost ring and is composed of microscopic particles. It is very diffuse and stretches between the orbits of two of Saturn's moons, Mimas and Titan.

Writing in the journal Science, scientists show how a plume of icy water vapour bursting out of the South Pole of Enceladus replenishes the water particles that make up the E-ring and creates a dynamic water-based atmosphere around the small moon. The E-ring is Saturn's outermost ring and is composed of microscopic particles. It is very diffuse and stretches between the orbit of two of Saturn's moons, Mimas and Titan.

Scientists discovered the dynamic atmosphere during three separate fly-bys of Enceladus by the Cassini spacecraft in February, March and July 2005.

Measurements of the temperature of Enceladus showed that there is a concentration of heat around the South Pole, with the hottest point located over one of the fractures in the planet's surface. The scientists believe that this heat signature shows internal processes within Enceladus that are causing the icy plume, by heating the moon's ice.


This enhanced color view of Enceladus is of the southern hemisphere and includes the south polar terrain marked by blue fractures. This image is a mosaic created from 21 false-color frames taken during the Cassini spacecraft's close approaches to Enceladus on March 9 and July 14, 2005. (Photo courtesy NASA/JPL/Space Science Institute)
Enceladus is a small moon, just 505 kilometers (314 miles) across, but it is highly reflective due to the fresh layer of snow and ice on its surface, the scientists said. The icy geysers at the south pole, erupting from a series of cracks, appear to be pumping a continuous flow of water particles into the area above the moon. Much of the material falls back to the surface as snow.

High-resolution Cassini images show icy jets and towering plumes ejecting large quantities of particles at high speed.

Scientists examined several models to explain the process. They ruled out the idea that the particles are produced by or blown off the moon's surface by vapor created when warm water ice converts to a gas.

Instead, scientists have found evidence that the jets might be erupting from near-surface pockets of liquid water above 0 degrees Celsius (32 degrees Fahrenheit), like cold versions of the Old Faithful geyser in Yellowstone National Park.

"We previously knew of at most three places where active volcanism exists - Jupiter's moon Io, Earth, and possibly Neptune's moon Triton. Cassini changed all that, making Enceladus the latest member of this very exclusive club, and one of the most exciting places in the solar system," said Dr. John Spencer, Cassini scientist at the Southwest Research Institute.

"Other moons in the solar system have liquid-water oceans covered by kilometers of icy crust," said Dr. Andrew Ingersoll, imaging team member and atmospheric scientist at the California Institute of Technology, Pasadena. "What's different here is that pockets of liquid water may be no more than tens of meters below the surface."

"Our search for liquid water has taken a new turn. The type of evidence for liquid water on Enceladus is very different from what we've seen at Jupiter's moon Europa, said Dr. Peter Thomas, Cassini imaging scientist at Cornell University.

"On Europa the evidence from surface geological features points to an internal ocean. On Enceladus the evidence is direct observation of water vapor venting from sources close to the surface," Thomas said.


Enceladus and Saturn's icy rings. Images taken using red, green and blue spectral filters were combined to create this natural color view. The images were taken using the Cassini spacecraft wide-angle camera on January 17, 2006 at a distance of 200,000 kilometers (124,274 miles) from Enceladus. (Photo courtesy NASA/JPL/Space Science Institute)
In the spring of 2008, scientists will get another chance to look at Enceladus when Cassini flies within 350 kilometers (220 miles), but much work remains after Cassini's four year prime mission is over.

"There's no question that, along with the moon Titan, Enceladus should be a very high priority for us. Saturn has given us two exciting worlds to explore," said Dr. Jonathan Lunine, Cassini interdisciplinary scientist at the University of Arizona.

Announced by the Cassini Imaging Science Team in Friday's issue of the journal "Science," the Enceladus water theory is bolstered by measurements from the Cassini Plasma Spectrometer (CAPS), as reported in the same issue by a team led by Robert Tokar of Los Alamos National Laboratory. CAPS was partly designed and built at Los Alamos.

"During the July 14 close flyby we began getting signatures, far from Enceladus, of water ejection," said Tokar. "From the deflections we could measure of the ionized gas in the magnetosphere, it was erupting at 100 kilograms per second (220 pounds per second), and the data are consistent with measurements from the spacecraft's other instruments."

"It is actual H20 molecules," said Tokar, referring to the chemical designation for water.

"Our paper, with 12 coauthors from U.S. and Europe, looks at the plasma of hydrogen, water and electrons in the ionized gas of the magnetosphere. The magnetosphere itself deflects in the vicinity of Enceladus, and we measure the plasma and that deflection," explained Tokar. "That is how we were able to determine the amount of water being ejected."