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Last Updated: Thursday, 8 February 2007, 20:45 GMT
Saturn moon's cosmic graffiti art
The tiger stripes mark the southern polar region of Enceladus (Nasa/JPL/SSI)

Saturn's moon Enceladus is a "cosmic graffiti artist", with geysers which spray out material that eventually settles over other satellites.

Hubble Space Telescope observations show how material from Enceladus alters the appearance of its neighbours.

One of Saturn's rings - the E ring - is largely made up of icy material from Enceladus' volcanic plumes.

These particles then collide with other moons that orbit within the E ring, coating their surfaces with material.

Anne Verbiscer from the University of Virginia and colleagues measured the reflectivity, or "albedo" of the saturnian satellites.

They concluded that interactions with E ring particles, ultimately from Enceladus' plumes, produced high albedos on the moons Tethys, Mimas, Dione and Rhea.

With a diameter of 500km (310 miles), Enceladus is a relatively small moon.

"Inevitably, material from Enceladus impacts all satellites orbiting within the E ring, enhancing their albedos at the hands of a diminutive giant," the researchers write in Science.

Enceladus is thought to have reservoirs of near-surface liquid water that erupt to form geysers.

These jets have been observed erupting from a "hot spot" in the moon's south polar region.

"We knew the E ring had a considerable extent from Mimas to beyond Tethys. So naturally, satellites orbiting within there are going to get coatings of this icy material," said Professor Carl Murray, from Queen Mary in London, who was not an author on the Science paper.

Prof Murray, who is a co-investigator on the Cassini-Huygens mission, added: "Anything more we can find out about the E ring is important because it is the material that came from under the surface of Enceladus. We believe there is a source of liquid water under the surface."

The Cassini spacecraft reached Saturn in July 2004 to study the planet, its rings and its moons.

On a flyby of Enceladus, it was able to sample and analyse material ejected by the south polar volcanic plume.


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