A Hidden Ocean on One of Jupiter's Moons?

Washington--Images from Jupiter's moon Europa released at a NASA press conference here today are wowing planetary scientists, who believe they are seeing yet more signs that beneath Europa's icy surface lies an ocean. An ocean--plus the hot, chemical-laden volcanic vents envisioned on any ocean's floor--could have produced life deep within Europa.

The Europa images are literally hot off the press--NASA received them only yesterday from the Galileo spacecraft in orbit around Jupiter. Describing the scene in the words of her young daughter, Arizona State University planetary geologist Kelly Bender says Europa's surface resembles "a person with the skin peeled off"--a sinewy mass of muscles and veins. More geologically speaking, the fine detail and optimal lighting of these best ever images revealed irregular ridges surrounded by dark material, as if volcanic eruptions had spewed debris to either side of cracks in the crust.

In another sign that Europa is still hot inside, perhaps even hot enough to be liquid, Bender pointed to dark bands with ridges down the middle and parallel lines on either side. To her, the ridges look suspiciously like Earth's volcanic midocean ridges, where melted rock wells up to form new crust that spreads away from the ridge. All this icy volcanism could be quite young, she added, given the dearth of meteorite impact craters on Europa. Only one crater, 3 kilometers in size, is obvious in the released image; the rest have presumably been erased by volcanic activity.

Planetary geologists won't have much time to ponder their enticing new images before Galileo swings past Europa next Wednesday. This time the spacecraft will pass so close that the image resolution will be 20 times better than in earlier images.