Broken ice on Europa

. Dark, linear crack-like features (top right) extend for thousands of kilometers across Jupiter’s moon Europa. They are believed to have formed when the satellite’s thin, icy crust fractured, separated and was filled by a dirty slush from a possible ocean below. The long cracks were most likely caused by tides raised on Europa by the gravitational pull of Jupiter. This image, about 770 kilometers wide, was taken from the Galileo spacecraft on 27 June 1996. (Courtesy of NASA and JPL.)

Copyright 2010, Professor Kenneth R. Lang, Tufts University