A team of international astronomers this week reported that a salt-water reservoir is the likely source of geyser plumes observed on Enceladus - one of Saturn's moons.

Joshua Colwell, a University of Central Florida physics professor who has been studying Saturn and its surrounding moons for years, said the discovery made by a team of astronomers from Germany, the United Kingdom and the University of Colorado at Boulder is significant because it rules out several theories about the source.

Since researchers found geysers on Enceladus in 2005, several theories have been proposed regarding the cause of the plumes, first detected by NASA's Cassini spacecraft in 2005 and again in 2007.

"This study of the distribution of different compositions of ice grains within the plumes makes the liquid reservoir model the most likely representation of what is actually going on," said Colwell, who was not part of the team, but whose own recent research has contributed to understanding geysers.

Frank Postberg, an astrophysicist at the University of Heidelberg in Germany, led the team, which published its findings this week in Nature .

Enceladus is more than 300 miles wide and has five sister moons orbiting Saturn. Colwell published a study in Nature in 2008 that showed the composition of the moon's geysers was water vapor. He also contributed to a paper published June 9 in Geophysical Research Letters that helped explain the composition of the vapor and the structure of the geysers. Colwell's team used data collected from Cassini's Ultraviolet Imaging Spectograph to come up with its conclusions.

Because Saturn is on the edge of the solar system, finding liquid is an interesting prospect. Water or water ice has only been found a handful of times.

"It broadens our thinking about where habitable worlds may reside in this and other planetary systems," Colwell said.

After reading Postberg's study, he is eager to see what else Enceladus will tell us in the future, as researchers worldwide study data collected by Cassini.

The Cassini mission launched from the Kennedy Space Center in 1997 and has been orbiting Saturn and studying its rings and moons since July 2004.

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