Titan's atmosphere is approximately 95% nitrogen. However, in a way that dramatically differs from Earth's own mostly-nitrogen atmosphere, Titan's atmosphere has very little oxygen. Indeed, the remainder of Titan's atmosphere is almost entirely composed of methane--along with small qunatities of other gases, such as ethane. At the extremely cold temperatures that are found at Saturn's great distance from the heat of our Star, Titan's methane and ethane can accumulate on its icy surface to form pools of liquid.
Titan: Titan, the tormented, hydrocarbon-slashed largest moon of Saturn--and the second largest moon in our Solar System, after Ganymede--could possess a subsurface, salty ocean that may well be as salty as the Dead Sea on Earth. The salty water could begin approximately 31 to 62 miles beneath Titan's icy shell, according to recent estimates. Meanwhile, on Titan's smog enshrouded surface, "life as we do not know it" could swim in alien lakes and rivers that flow with liquid methane and ethane hydrocarbons--instead of water.
Dr. Thomas and his team at Cornell University have tried to peer into the mysterious interior of the weird little Space egg that is Methone. They started out with the hypothesis that Saturn's relentless strong gravity pulls the little moon into an elongated shape, just like Earth's own large Moon raises ocean tides on our own planet. Then the team went on to calculate how dense the little moon would have to be for its own gravity to counteract those intense tidal forces and create its strange egg-shape.