Saturn's moons Tethys, Enceladus and Mimas are shown in this image taken by the Cassini spacecraft on December 3, 2015. Tethys is above the rings, Enceladus is below the rings in the center of the image, and Mimas is below and to the left. Cassini has been exploring Saturn and its moons since 2004. The mission is scheduled to end in September 2017.