Inside the Galilean satellites

Inside the Galilean satellites

Fig. 9.10 . Cutaway views of the possible internal structures of the Galilean satellites. Ganymede is at the lower left, Callisto at the lower right, Io on the upper left, and Europa on the upper right. The surfaces of the satellites are mosaics of images obtained in 1979 by the Voyager 1 or 2 spacecraft, and the interior characteristics are inferred from gravity field and magnetic field measurements from the Galileo spacecraft. With the exception of Callisto, all the satellites have iron-nickel cores (gray) surrounded by rock (brown) shells. Ios rock or silicate shell extends to the surface, while the rock layers of Ganymede and Europa are surrounded by shells of water ice or liquid water (white and blue). Callisto seems to be a relatively uniform mixture of comparable amounts of ice and rock. Galileo images of Europa suggest that a liquid water ocean might now underlie a surface layer of water ice. (Courtesy of NASA/JPL.)

Copyright 2010, Professor Kenneth R. Lang, Tufts University