The Earth is the only planet we are sure has liquid water on its surface. One of the other celestial bodies in our solar system that is thought to have lakes of liquid material on the surface is the Saturn moon Titan. Titan’s lakes are not filled with water.
Rather than water like we have here on Earth, the lakes on Titan are believed to be filled with hydrocarbons like methane, ethane, and other substances. It’s not a place where you would want to light a match, that’s for sure.
It’s very cold on the surface of Titan with temps estimated to be in the area of -180C. Those cold temperatures allow the hydrocarbons to exist in a liquid state. The surface of Titan is believed to have lakes, rivers, dunes, and seas all filled with these liquid hydrocarbons.
Scientists have recently discovered something very interesting about Titan and its lakes. The discovery has to do with waves in those lakes. Scientists have detected ripples on Titan’s sea called Punga Mare. That is Titan’s largest hydrocarbon liquid body. It is believed to have 9000 cubic kms of liquid methane in it. If accurate, that is 40 times the amount of liquid methane that the Earth has on the entire planet. NASA released images of Titan’s lakes late last year.
SOURCE: The Almagest