Hypeline World News Report

- Tethys-one of Saturn’s moons may once have harbored a liquid ocean beneath its icy surface, scientists reported to a conference in Houston, Texas.

Tethys is a mid-sized satellite with a density close to that of pure ice.

There is a large valley system visible today which could have formed when the crust was repeatedly heated and under great strain.

Tidal heating, followed by cooling which froze Tethys’ ocean, could have formed the giant Ithaca Chasma rift.

Details were presented here at the 39th Lunar and Planetary Science Conference.

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

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

The resulting tidal forces caused frictional heating of Tethys’interior,then at some point, the orbital interaction between Tethys and Dione became broken, and Tethys fell back into a less eccentric orbit. As it did so, it began to cool.

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

“We have a large rift system that brought water to the surface, so it seems likely that this happened,” Ms Chen explained.

Tethys is a few of icy Solar System bodies thought either to have a subsurface ocean today, or to have had one in the distant past.

They include Jupiter’s moons Europa and - potentially - Callisto, researchers also think Saturn’s moon Enceladus may have liquid water beneath the surface.