Saturn's moon Tethys, Cassini image

Saturn's moon Tethys. Enhanced colour mosaic satellite image showing unusual arc-shaped reddish streaks cut across the surface of Saturn's moon Tethys. Tethys (1060 kilometres diameter) is composed almost entirely of pure water ice. The high reflectivity (albedo) of the icy surface makes Tethys the brightest moon orbiting Saturn and one of the brightest objects in the solar system. The red streaks are narrow lines on the surface, only a few kilometres wide but several hundred kilometres long. Their origin is currently unknown but possibilities include ideas that the reddish material is exposed ice with chemical impurities, or the result of outgassing from inside Tethys. The streaks could also be associated with features like fractures that are below the resolution of the available images. Composed from images obtained by the Cassini Orbiter, on 11th April 2015.