Concentric Rings Surrounding Valhalla
Jet Propulsion Laboratory https://www.jpl.nasa.gov/ Jan. 9, 1997
The concentric rings surrounding Valhalla are perhaps the most distinctive geological feature on Callisto. This Voyager 1 close-up shows a segment of the ridged terrain. The presence of superimpact craters shows that the rings formed early in Callisto's history; however, the density of craters is less here than on other parts of the satellite, where the surface is older.