Saturn's moon Tethys may once have harbored an ocean

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London, March 16 : Scientists have suggested that Tethys, ne of Saturn's moons, may once have harbored a liquid ocean eneath its icy surface.

According to a report in BBC News, Tethys is a mid-sized atellite with a density close to that of pure ice, which is eavily cratered and contains cracks caused by faults in the ice.

Evidence for the watery history of Tethys emerged with the iscovery of an enormous valley on its surface, which has been ame Ithaca Chasma.

This valley is about 65 kilometers (40 miles) wide and extending rom above the center to the extreme left. Covering three-fourths f Tethys' circumference, this fissure is about the size cientists would predict if the moon was once fluid and its crust ardened before the interior.

According to Erinna Chen and Francis Nimmo from the University of alifornia, Santa Cruz, tidal heating, followed by cooling which roze Tethys' ocean, could have formed the giant Ithaca Chasma ift.

Calculations by Chen and Nimmo, from the University of alifornia, Santa Cruz, show that tidal interactions were the nly viable way of providing the amount of heat associated with he formation of Ithaca Chasma.

They propose that Tethys' orbit around Saturn was once perturbed y gravitational interactions with another moon - Dione - which ade Tethys' orbit more "eccentric".

The resulting tidal forces caused frictional heating of Tethys' nterior.

But at some point, the orbital interaction between Tethys and ione was broken, and Tethys fell back into a less eccentric rbit. As it did so, it began to cool.

According to the researchers, freezing of a liquid ocean would ave generated sufficient stresses in the crust to form Ithaca hasma.

Chen told the BBC that there was no way of knowing exactly how eep the ocean was, but speculated that it could have been 100km eep at some point in Tethys' past.

Tethys joins a club of icy Solar System bodies thought either to ave a subsurface ocean today, or to have had one in the distant ast.

ANI

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