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Saturn gets water from its moon!

The 14-year mystery behind the source of the water in Saturn’s upper atmosphere has been solved. It has been discovered that the planet's moon forms a huge halo of...

india Updated: Jul 27, 2011 18:58 IST

The 14-year mystery behind the source of the water in Saturn’s upper atmosphere has been solved.

The European Space Agency's Herschel Space Observatory has discovered that the planet's moon Enceladus forms a huge halo of water vapour around Saturn.

Herschel’s latest results mean that Enceladus is the only moon in the Solar System known to influence the chemical composition of its parent planet.

Enceladus expels around 250 kg of water vapor every second, through a collection of jets from the south polar region known as the ‘Tiger Stripes’ because of their distinctive surface markings.

These crucial observations reveal that the water creates a doughnut-shaped torus of vapor surrounding the ringed planet.

The total width of the torus is more than 10 times the radius of Saturn, yet it is only about one Saturn radius thick. Enceladus orbits the planet at a distance of about four Saturn radii, replenishing the torus with its jets of water.

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

Saturn’s atmosphere is known to contain traces of gaseous water in its deeper layers. A particular enigma has been the presence of water in its upper atmosphere.

First reported in 1997 by teams using ESA’s Infrared Space Observatory, the source of this water was unknown until now. Computer models of these latest Herschel observations show that about 3-5 pc of the water expelled by Enceladus ends up falling into Saturn.

“There is no analogy to this behavior on Earth,” said Paul Hartogh, Max-Planck-Institut für Sonnensystemforschung, Katlenburg-Lindau, Germany, who led the collaboration on the analysis of these results.

“No significant quantities of water enter our atmosphere from space. This is unique to Saturn,” he added.

First Published: Jul 27, 2011 15:43 IST