Titan is the largest of Saturn's moons. It is about 3200 miles in diameter. This makes it larger than both Mercury and Pluto. It is the second largest in the solar system, rivaled by one of Jupiter's moons. It is the only moon in the solar system known to have a dense atmosphere. Triton, a moon of Neptune is the only other moon known to even have an atmosphere.

The Atmosphere

Scientists believe Titan's atmosphere is similar to that of the early Earth. It's chemistry is believed to be similar to that of Earth several billion years ago. It is so thick no previous spacecraft were able to see the surface. It has a thick smoglike cloud layer around 200 miles above the surface. The atmospheric pressure is 60% greater than that of the Earth.

Life On Titan??

Scientists believe in the possibility of life on Titan for several reasons. First, the atmosphere is very similar to that of Earth, composed mostly of nitrogen, and containing several other organic components. They believe there is a possibility that there is liquid on the surface, although the surface has not yet been seen. They believe chemical processes turn the methane in the atmosphere into several different organic molecules, including hydrogen cyanide, the basic building block of amino acids.

Here is a link to what bodies in the solar system scientists feel may be the best for harboring life:

Finally, one reason scientists feel there may not be life on Titan is simply that it may be too cold, with temperatures around -290 degrees Farenheit.