
Titan, Saturn's largest moon, is seen in front of the planet as Titan undergoes seasonal changes in this view from NASA's Cassini spacecraft. The moon measures 3,200 miles, or 5,150 kilometres, across and is larger than the planet Mercury. Cassini scientists have been watching the moon's south pole since a vortex appeared in its atmosphere in 2012.
Picture: REUTERS/ NASA/JPL-Caltech/SSI




