Jupiter from Europa. Computer artwork of a view towards Jupiter, across pack-ice like formations in the icy surface of Europa. Europa is the fourth largest of the many moons that orbit Jupiter. It is believed to be composed of silicate rocks with a layer of water ice covering the entire surface. This image is inspired by recent discoveries of regions that look much like pack-ice on Earth's polar seas during spring thaws. The perspective is from an altitude of several thousand feet. The large crater in the foreground (lower right) is about a half-mile in diameter.