Aliens In A Slushy Sea?

By Jeffrey Kluger

At week's end space scientists were buzzing about fresh confirmation of year-old evidence that there is a dusting of polar ice on the moon--ice that could help a community of astronauts survive. Almost lost in the excitement was news from a far more distant and far wetter world. According to the crispest images yet from the Galileo Jupiter probe, there is more reason than ever to think that beneath the icy skin of the Jovian moon Europa there lies a warm, amniotic sea in which heat, moisture and organic chemicals may have already allowed life to take hold.

The new evidence comes from a Europa flyby in which Galileo barnstormed the little moon at an altitude of just a few hundred miles. Soaring over a region known as the Conamara Chaos, the spacecraft photographed an area in which the moon's thin skin of ice appears to have buckled as a result of turbulent water moving just beneath the frozen crust. The crumpling gave the ice a washboard topography made up of a series of parallel cliffs, each the size of Mount Rushmore. Elsewhere the spacecraft spotted bright crustal fractures crisscrossing older, darker ones, suggesting that the ice is being cracked and recracked by similar subsurface sloshing. Still elsewhere the ship photographed a crater whose floor seems to have swelled up from beneath--its central peak pushed above its rim--probably the result of slushy seas deforming the crater after it was created. "We'd never seen the surface at this resolution," says James Head, a Galileo scientist. "It's a little bit like putting it under a microscope."

Galileo has completed its original planned tour of the Jovian system and is on a two-year extended mission to study several of Jupiter's moons. Six other flybys of Europa are scheduled before the sturdy spacecraft, which left Earth almost nine years ago, at last shuts down in December 1999. On one pass, Galileo will observe Europa from an angle that will allow scientists to look for telltale volcanic plumes rising from its edge. If found, they'll indicate that the moon is warmer than it seems--and an even likelier incubator for extraterrestrial life.

--By Jeffrey Kluger