Hydrocarbon lakes on Titan, Cassini image. The lakes are the darker regions and are located around the north polar region of Titan, with a large and prominent one just below the terminator (day/night boundary) at centre. These lakes are thought to contain a mixture of methane and ethane. At this time, the north polar region was experiencing its winter. It is thought that the lakes evaporate during Titan's summer. The liquids are thought to be in a dynamic equilibrium with the atmosphere, as is the case with water on Earth. Numerous lakes have been found on Titan, some of which are so large that they have been called seas. Image taken by Cassini on 25th February 2007.