As the Huygens-Cassini probe flew by on July 22 , 2006 , its radar took pictures of the northern part of the planet ( which was in its winter ) , a number of large , smooth areas were found on the surface near the northern pole . Following a flyby on July 22 , 2006 , in which the Cassini spacecraft 's radar imaged the northern latitudes ( which are currently in winter ) , a number of large , smooth ( and thus dark to radar ) patches were seen dotting the surface near the pole .