Effects of LHB on Structure of Callisto and Ganymede (image) Southwest Research Institute Share Print E-Mail Caption 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. The surfaces are initially blue, indicating a uniform ice/rock mixture. Over time, repeated overlapping impacts remove all of the rock from the moons' outer layers. The right hand side shows a vertical slice through the spinning globe, allowing us to see the growth of the core (black). Each frame of the movie records 50 new impacts onto each moon. Callisto receives 2,600 impacts, but Ganymede receives 5,200. When the late heavy bombardment on Callisto is complete, the movie of Callisto stops, but Ganymede continues to experience an additional 2,600 impacts (so the movie of its evolution has more frames). The final frame of the movie shows the structure of the moons at the end of the late heavy bombardment. Note that Ganymede's rock core is significantly larger than the core created in Callisto. Credit Southwest Research Institute Usage Restrictions Embargoed until 1 p.m. Eastern, Jan. 24, 2010 Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.