This close-up image of Callisto was taken by the Voyager 2 spacecraft. It shows a pair of ancient multi-ringed impact basins. The larger impact structure is known as Asgard, and is surrounded by concentric rings up to 1,050 miles (1,700 km) in diameter. A second ringed structure is about 310 miles (500 km) in diameter. The icy materials excavated by the younger craters contrast sharply with the darker and redder coatings on older surfaces of Callisto.
NASA / JPL Image