Saturn moon 'once had ocean'

The Ithaca Chasma is thought to be a very old structure

(BBC) -- One of Saturn's moons may once have harboured a liquid ocean beneath its icy surface, scientists have told a major conference in Houston, Texas.

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

But a large valley system visible today must have formed when the crust was being heated and under great strain. full story