Saturn’s largest moon is covered in seas and lakes of liquid hydrocarbons – and one sea has now been found to be filled with pure methane, with a seabed covered by a sludge of organic-rich material, and possibly surrounded by wetlands.
Of all the moons in the Solar System, Titan is the only one with a thick atmosphere and large liquid reservoirs on its surface – in some ways making it more like a planet such as Earth.
Both Earth and Titan have atmospheres dominated by nitrogen, over 95% in Titan’s case. However, unlike Earth, there is little oxygen: the remaining is mostly methane, with a small amount of hydrogen, and trace amounts of other gases such as ethane. … (ESA)