Figure 6-28 RIVUXG Moving Ice on Europa and Earth (a) Sometime after a series of ridges formed in this region of Europa’s surface, the icy crust broke into “rafts” that were moved around by an underlying liquid or plastic layer. The colors in this Galileo image may be due to minerals that were released from beneath the surface after the crust broke apart. (b) Europa’s ice rafts are analogous to ice floes on Earth, created when pack ice breaks up, as in this spacecraft view of part of the Canadian Arctic.