The concentric rings surrounding Valhalla are perhaps the most distinctive geological feature on Callisto. This NASA Voyager 1 close-up shows a segment of the ridged terrain.
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.
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