This image of Saturn's moon Iapetus was captured by NASA's Cassini spacecraft. It shows the stark contrast in surface features on this amazing moon. Iapetus is 914 miles, (1,472 km) in diameter, making it Saturn's third largest moon. A gigantic impact crater can be seen near the bottom of the image. Known as Engelier, it is 280 miles (450 km) in diameter. The most striking features of Iapetus is the contrast between the bright and dark areas. The light areas actually represent the base color of the icy moon. The dark areas represent material that has been deposited on top.