Valhalla multi-ring basin on Jupiterís moon Callisto

Valhalla multi-ring basin on Jupiterís moon Callisto

Fig. 9.23 . The icy crust of Callisto is as rigid as steel, and it therefore retains the scars of an ancient bombardment by impacting meteorites. An exceptionally powerful impact produced a multi-ring basin (top center), named Valhalla after the home of the Norse gods. The extensive system consists of a light floored central basin some 300 kilometers in diameter, surrounded by at least eight concentric mountainous ridges, which resemble ripples produced on a pond by a rock striking the water. The impacting object on Callisto apparently punctured the surface and disappeared. Today only the frozen, ghostlike ripples remain. The great number of rings observed around this basin on Callisto is consistent with the moonís low density and probably low internal strength. Although there are very few large craters, the rest of Callisto is pockmarked with smaller impact craters that are flat for their size, and many of them have bright rims that resemble clean water ice splashed upon the dirtier surface ice. This image was taken from the Voyager 1 spacecraft on 6 March 1979. (Courtesy of NASA/JPL.)

Copyright 2010, Professor Kenneth R. Lang, Tufts University