This infrared image of Titan, Saturn's largest moon, shows extensive cloud cover over Titan's North Pole. This image was captured by the Cassini spacecraft on December 29, 2006. At the time, this vast system of clouds covered an area half the size of the United States. Rain or snow falling from clouds like these may fill Titan's polar lakes with methane and/or ethane.
Image courtesy of NASA/JPL/University of Arizona.