This image of Saturn's icy moon Tethys was captured by NASA's Cassini spacecraft. Tethys is 662 miles (1,066 kilometers) in diameter, making it Saturn's fifth largest moon. It has a low density, which means it is composed almost entirely of water ice. The surface of Tethys is extremely light and reflective. In fact, it is one of the most reflective objects in the Solar System. The surface of Tethys is heavily cratered. The largest crater is called Odysseus and is 280 miles (450 kilometers) in diameter. Odysseus is not visible in this image.