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.
NASA's Cassini spacecraft has spotted mysterious reddish streaks on the surface of Saturn's icy moon Tethys. The red streaks are only a few miles wide but several hundred miles long. The images were taken in April. Scientists aren't sure what's causing the streaks.
This mosaic of Saturn's moon Mimas was created from images taken by Cassini in February 2010. A recent study indicates the moon may contain a liquid water ocean.
Cassini glided high above Saturn in October 2013 to capture this 36-image mosaic of the ringed planet. The colors of the planet appear natural, just as the human eye would see them.
Plumes of water ice and vapor shoot up from the surface of Saturn's moon Enceladus in this two-image mosaic taken by Cassini in November 2009. Analysis by NASA scientists indicated that water can reach the Saturnian moon's surface.
A small, bright blip can be seen on the outermost edge of Saturn's rings in this image taken in April 2013. The bump in the smooth ring structure is an icy object that could provide clues to how Saturn's moons formed.
This false-color image of Saturn's north polar storm looks like a giant red rose surrounded by green foliage. Measurements indicate the storm's eye is a staggering 1,250 miles across with cloud swirling as fast as 330 mph.
Saturn's rings cast a narrow shadow on its surface in this image taken in August 2009.
The scars of time and space mark the surface of Saturn's moon Enceladus. Saturn has at least 62 moons in its orbit.
The Saturn-facing side of Enceladus is illuminated by light bouncing off the planet. Plumes of water ice can be seen streaming off the moon's southern pole.
Saturn's moon Rhea is seen from approximately 174,181 miles away in this March 2013 image.
Rhea's surface is pockmarked with craters from billions of years of impacts. The moon is Saturn's second-largest, with a diameter of 949 miles.
Saturn's largest moon, Titan, has a diameter of 3,200 miles. It looks like a fuzzy orange ball because of its atmosphere.
Though it's the largest moon orbiting Saturn, Titan is dwarfed by Saturn itself.
Saturn has a small moon called Dione orbiting about 234,000 miles away. That's about the same distance Earth is from its moon.
The surface of Dione is seen in this May 2012 image.
Tethys, top left, is dwarfed by Saturn as it orbits the planet, though scientists think the moon is much larger than Saturn's ring system.
The Odysseus Crater spans 280 miles across the northern hemisphere of Tethys.