The movies show the effect of an outer solar system late heavy bombardment on the interior structure of Callisto (top) and Ganymede (bottom). The left hand side shows the surface of each moon as it suffers repeated impacts that melt its outer layers and clean out rock suspended in its ice. Colors indicate density, with black showing rock, blue showing mixed ice and rock, and lighter shades of blue indicating a decreasing rock fraction.

Credit: Southwest Research Institute