Long ago Titan was thought to be the largest moon in the solar system. New observations have revealed that Ganymede, one of Jupiter’s moons is even larger. Part of the reason for the mix-up is the thick, dense atmosphere that surrounds Titan, obstructing surface views. Titan, like Ganymede, is larger than both Mercury and Pluto. Until recently, a clear view of the surface was not available. In late 2004 the Cassini orbiter began to study Titan, and in January of 2005, the Huygens probe actually landed on the surface and began transmitting photographs of the surface. Numerous dark areas can be seen near the North Pole that are actually seas and lakes of liquid hydrocarbons. Methane for example is 'natural gas' on the Earth, yet is liquid at Titan's temperatures. It would actually be possible to sail on a boat on the lakes with a good space suit.
The atmosphere that encircles the moon is 50% greater than that around Earth. Composed of mainly nitrogen, similar to the Earth’s atmosphere, the atmosphere of Titan also has 6% argon and some methane along with many other organic compounds. This combination of gases, combined with sunlight, has created thick smog, similar to that seen over large cities. There are also clouds of ethane and methane obstructing the view of the surface. From the Huygens probe there is still much to discover, but some initial results show "lakes" and "rivers" that are currently dried up and are mostly crater-free surfaces. At least one of the lakes has been verified to have liquid ethane at the present time. In 2009 the Cassini orbiter captured sunlight reflecting off surface, confirming the presence of liquid on Titan in the area covered with many large, lake-shaped basins. While at any given time it is usually not raining on the surface, there is some evidence of precipitation and erosion on the surface. There are also cloud formations seen in various regions that may be raining from time to time.
There are three datasets available for Titan. This dataset is in black and white, there is one in color as well as a black and white map with RADAR swaths from Cassini overlaid. The RADAR swaths show some of the seas, lakes and rivers of liquid hydrocarbons near the North Pole.