Geysers of icy material are erupting from Saturn’s tiny moon Enceladus, providing incontrovertible proof that the moon is geologically active. Recent images taken by the Cassini spacecraft, which has toured the Saturnian system since July 2004, show the jets shooting far above the icy satellite’s south-polar region.

ICE FOUNTAINS. Backlit by the sun, Saturn’s moon Enceladus shows icy material streaming from a source somewhere in the body’s south-polar region. JPL/NASA, Space Science Institute

A spectrometer on Cassini had previously detected a large cloud of water vapor above the south pole when the craft passed within 175 kilometers of Enceladus last July (SN: 8/27/05, p. 141: Available to subscribers at
). Researchers conjectured that linear surface fractures at the pole, dubbed tiger stripes, provide a conduit for ice to vaporize from the moon and continually replenish the cloud. The moon is known to feed material to Saturn’s tenuous E ring. The new images, combined with spectra that identify ice particles in the geysers, suggest how that transfer could be made.

Pictures released by NASA show that the jets soar up to 300 km above the surface of Enceladus. The moon itself is only about 300 km in diameter.

For planetary scientists, “there is little that can compare to the sighting of activity on another solar system body,” says Cassini imaging team leader Carolyn Porco of the Space Science Institute in Boulder, Colo. “This has been a heart stopper.”

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