From NASA's Astronomy Picture of the Day archives, this Voyager spacecraft image of Europa's surface is suggestive of sea ice on Earth. The criss-crossing dark streaks may indeed be cracks in its ice-covered surface caused by Jupiter's tidal stresses accompanied by the freezing and expansion of an underlying layer of water.
The Galileo Probe's flyby of Europa, Jupiter's ice-covered moon showed a fractured and frozen terrrain. Only a few impact craters are apparent though, implying a geologically young surface. So far, Galileo's findings lend support to the exciting possibility that liquid water once existed and may still exist beneath Europa's surface.