Photos: Best photos of Saturn--and the winners are

3. Changes in the surface of Titan can be observed as the Cassini probe makes regular passes by the giant moon. The image on the right, taken in December 2005, shows a very bright south polar cloud system. The clouds were barely visible in the image on the left, taken in October 2005.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency.

Photo by NASA/JPL/University of Arizona