Saturn’s moon Tethys may once have harbored an ocean

March 16th, 2008 - 12:17 pm ICT by admin  

London, March 16 (ANI): Scientists have suggested that Tethys, one of Saturn’s moons, may once have harbored a liquid ocean beneath its icy surface.

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

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

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

According to Erinna Chen and Francis Nimmo from the University of California, Santa Cruz, tidal heating, followed by cooling which froze Tethys’ ocean, could have formed the giant Ithaca Chasma rift.

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

They propose that Tethys’ orbit around Saturn was once perturbed by gravitational interactions with another moon - Dione - which made Tethys’ orbit more “eccentric”.

The resulting tidal forces caused frictional heating of Tethys’ interior.

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

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

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

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

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