Titan (also known as Saturn VI) is the largest moon of Saturn. It is the only natural satellite known to have a dense atmosphere, and the only object other then Earth where clear evidence of stable bodies of liquid water have been found.
Titan is the sixth ellipsoidal moon from Saturn. Frequently described as a planet-like moon, Titan has a diameter roughly 50% larger than the Moon and is 80% more massive. It is the second largest Moon in the Solar System, after Jupiter's moon Ganymede. Titan is larger by volume then Mercury, though it only has 41% of its Mass. Titan was the first known moon of Saturn, and was the fifth moon discovered (not including Earth's Moon) to be discovered.
Titan is primarily composed of water ice and rocky material. The atmosphere of Titan is largely composed of nitrogen, minor components lead to the formation of methane and ethane clouds and nitrogen-rich organic smog. The climate - including wind and rain - creates surface features similar to those of Earth, such as dunes, rivers, lakes and seas (probably of liquid methane and ethane), and deltas, and is dominated by seasonal weather patterns like Earth. With its liquids (both surface and subsurface) and robust nitrogen atmosphere, Titan's methane cycle is viewed as an analog to Earth's water cycle, although at a much lower temperature.