This is the heavily cratered moon Mimas (398 kilometres across). The enormous crater at the top of this image, named Herschel, is about 130 kilometres wide and 10 kilometres deep.
The image was taken in visible light with the Cassini-Huygens spacecraft narrow-angle camera on 3 July 2004, from a distance of 1.7 million kilometres from Mimas. The image scale is 10 kilometres per pixel. The image has been magnified by a factor of two to aid visibility.