SCIENCE LAB *SATURN : ' DEATH STAR '

SECRETS OF A SATURN MOON

New research is converting some skeptics to the idea that tiny, icy Mimas may be full of liquid.

With a large crater carved out of its surface, Mimas, 250-mile-wide moon of Saturn, resembles the Death Star in '' Star Wars. ''

For eight years, scientists have considered the possibility that Mimas, seemingly just a pockmarked ball of ice, might have an ocean 14 to 20 miles, or 23 to 32 kilometers, below its surface.

Such ocean worlds - Europa at Jupiter and Enceladus at Saturn, to name two - have jumped to the top of lists for scientists who are considering places where life could have arisen in the solar system.

But unlike other moons known to possess under-ice oceans, Mimas has a surface with no cracks or hints of melting that might suggest liquid within. It has also stretched scientific credulity to think that the interior of a moon as small as Mimas could be warm enough for an ocean to remain unfrozen.

Alyssa Rhoden, with the Southwest Research Institute in Boulder, Colo., doubted the possibility of an ocean.

But along with Matthew Walker of the Planetary Science Institute, headquartered in Tucson, Ariz, she devised a computer simulation that changed her mind.

They found that tidal forces at play between Saturn and Mimas could generate enough heat enough to maintain a liquid ocean.

''It works really beautifully,'' Dr. Rhoden said.  [ Kenneth Chang ]