Saturn's water comes from one of its moons

PARIS, July 26 (UPI) -- European astronomers say finding that water expelled from the moon Enceladus rains down on Saturn solves the mystery of water in the planet's upper atmosphere.

The discovery by the European Space Agency's Herschel space observatory means Enceladus is the only moon in the solar system known to influence the chemical composition of its parent planet, an ESA release said Tuesday.

About 500 pounds of water ejected every second from jets in the south polar region of Enceladus create a huge doughnut-shaped torus of water vapor surrounding the ringed planet.

Despite its enormous size, the torus has escaped detection until now because water vapor is transparent to visible light but not at the infrared wavelengths Herschel was designed to detect, the ESA said.

The source of this water was unknown until now.

"There is no analogy to this behavior on Earth," said Paul Hartogh of the Max-Planck-Institut in Germany, who led the analysis of the Herschel results.

"No significant quantities of water enter our atmosphere from space. This is unique to Saturn."