This close-up image of Saturn's rings was captured by NASA's Cassini spacecraft. Many fine details can be see in the rings, including the dark gaps and smaller ringlets. The dark area in the upper right corner of the image is the shadow of the planet Saturn falling across the rings. The tiny white spec just below the rings to the left of center is one of Saturn's smaller moons named Prometheus. Prometheus is only 53 miles (86 kilometers) across at its widest point. It is shaped somewhat like a potato, and resembles many of the asteroids in the main asteroid belt between Mars and Jupiter.