Titan's changing features. Three Cassini images of Titan, the largest moon of Saturn, showing changes in its features that indicate it is a dynamic world. The images were taken, from left to right, on 28th October 2005, 26th December 2005 and 15th January 2006. The December view (middle) shows the opposite hemisphere to the other two. This view shows a bright cloud system over the south pole and a hood over the north pole, both of which are not seen in the October and January images. This indicates that Titan has an active atmosphere. The bright region just south of the equator in the October and January images is called Tui Reggio, and is thought to be volcanic in origin. The images were taken at infrared wavelengths: 1.6 microns (blue), 2.01 microns (green) and 5 microns (red).