Titan

Titan (or 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 than Earth for which clear evidence of stable bodies of surface liquid has been found.

Titan is the sixth ellipsoidal moon from Saturn. Frequently described as a planet-like moon, Titan has a diameter 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, and is larger by volume than the smallest planet, Mercury, although only 40% as massive. Discovered in 1655 by the Dutch astronomer Christiaan Huygens, Titan was the first known moon of Saturn, and the fifth known satellite of another planet.

Titan is primarily composed of water ice and rocky material. Much as with Venus prior to the Space Age, the dense, opaque atmosphere prevented understanding of Titan's surface until new information accumulated with the arrival of the Cassini–Huygens mission in 2004, including the discovery of liquid hydrocarbon lakes in Titan's polar regions. The geologically young surface is generally smooth, with few known impact craters, although mountains and several possible cryovolcanoes have been found

In Saturn's moon Titan is believed that there may be some alien life forms , possibly based on the methane flowing rivers and causing the atmosphere contains methane rain .
According to data obtained by the Cassini probe methane rivers flowing on the surface of Titan , the Huygens probe also landed on Titan in 2005 showing the first images of Titan's surface , also I bring very interesting data.
The satellite of Saturn contains several chemical compounds based on hydrocarbons such as methane and ethanol compounds on Earth are produced by plants and animals decaying beneath the surface, that when these fermented in large quantities produce hydrocarbons such as oil, methane and ethanol , being trapped under the surface until it is extracted to burn and produce energy. But the question that leads to scientific head is, as these liquids have occurred in Saturn's moon Titan? , Well the simplest explanation is that methane and other chemicals found in the planet since its formation. Apart for the gas should have kept various chemical over millions of years , entirely possible reactions have occurred.

Anyway Titan hides many mysteries yet to be solved, a scientific research suggested that something is breathing Titan flowing hydrogen atmosphere and when it approaches the surface of Titan disappears. Although it is believed that it could be a chemical reaction undiscovered , has not ruled out the likelihood of bacterial forms or more complex but very alien life could be breathing in Titan.
No similar type of life is unknown, although some organisms on Earth are able to live in and even expel methane gas as waste , low temperatures of Titan a 180 below zero on average, make it impossible to survive , but who knows which may have arisen in the methane million years.