Saturn's moon Titan, cutaway artwork. Titan is the largest satellite of Saturn. It is known to have traces of complex hydrocarbon compounds in its nitrogen atmosphere. These form as sunlight acts on the methane in Titan's upper atmosphere. Clouds of ethane and ethane vapour would produce a rain of liquid hydrocarbons. Oceans of ethane may also exist on the surface. The cutaway through the atmosphere shows these oceans, and hypothetical land shapes. Saturn and its rings are visible in the background.