The Cassini spacecraft recently did a flyby of Saturn's moon, Titan and photographed a cloud roughly half the size of the continental United States. Earth based observations had previously showed the existence of the cloud system and it's movement throughout the moon's seasons. It is thought that this cloud moves between poles of the moon every season. Seasons on Titan last about 7 earth years. It is currently believed that the cloud systems on Titan are part of an evaporative cycle, called the 'methane-ologic cycle' that fills the lakes o

Saturn's moon Titan has lakes & rivers of some hydrocarbon (assumed methane), and methane rain according to Ellen Stofan of University College London and the California Institute of Technology who has been working on the Cassini probe mission.