Titan,the saturn's largest moon

Titan is the largest moon of Saturn. It is the only natural satellite known to have a dense atmosphere,[9] and the only object other than Earth for which clear evidence of stable bodies of surface liquid has been found.[10]
Titan is the sixth ellipsoidal moon from Saturn. Frequently described as a planet-like moon, Titan has a diameter 50% larger than Earth's natural satellite, 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.
Formation of Titan
The moons of Jupiter and Saturn are thought to have formed through co-accretion, a similar process to that believed to have formed the planets in the Solar System. As the young gas giants formed, they were surrounded by discs of material that gradually coalesced into moons. However, whereas Jupiter possesses four large satellites in highly regular, planet-like orbits, Titan overwhelmingly dominates Saturn's system and possesses a high orbital eccentricity not immediately explained by co-accretion alone

Climate
Titan's surface temperature is about 94 K (−179.2 °C). At this temperature water ice has an extremely low vapour pressure, so the little water vapor present appears limited to the stratosphere.[49] Titan receives about 1% of the amount of sunlight that Earth gets.[50]
Atmospheric methane creates a greenhouse effect on Titan's surface, without which Titan would be far colder.[51] Conversely, haze in Titan's atmosphere contributes to an anti-greenhouse effect by reflecting sunlight back into space, cancelling a portion of the greenhouse effect warming and making its surface significantly colder than its upper atmosphere.[52]
Titan's clouds, probably composed of methane, ethane or other simple organics, are scattered and variable, punctuating the overall haze.
Atmosphere
Titan is the only known moon with more than a trace of atmosphere. Its atmosphere is the only nitrogen-rich dense atmosphere in the Solar System aside from Earth's. Observations of its atmosphere made in 2004 by Cassini suggest that Titan is a "super rotator", like Venus, with an atmosphere that rotates much faster than its surface.[33] Observations from the Voyager space probes have shown that Titan's atmosphere is denser than Earth's, with a surface pressure about 1.45 times that of Earth's. Titan's atmosphere is about 1.19 times as massive as Earth's overall,[34] or about 7.3 times more massive on a per surface area basis. It supports opaque haze layers that block most visible light from the Sun and other sources and renders Titan's surface features obscure.[35] Titan's lower gravity means that its atmosphere is far more extended than Earth's.