Titan (moon) - Atmosphere

Atmosphere

Titan is the only known moon with more than a trace of atmosphere, and is the only dense, nitrogen-rich atmosphere in the Solar System aside from the Earth's. Observations of the 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. Observations from the Voyager space probes have shown that the Titanian 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, 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. Titan's lower gravity means that its atmosphere is far more extended than Earth's. The atmosphere of Titan is opaque at many wavelengths and a complete reflectance spectrum of the surface is impossible to acquire from orbit. It was not until the arrival of the Cassini–Huygens mission in 2004 that the first direct images of Titan's surface were obtained.

The atmospheric composition in the stratosphere is 98.4% nitrogen with the remaining 1.6% composed mostly of methane (1.4%) and hydrogen (0.1–0.2%). There are trace amounts of other hydrocarbons, such as ethane, diacetylene, methylacetylene, acetylene and propane, and of other gases, such as cyanoacetylene, hydrogen cyanide, carbon dioxide, carbon monoxide, cyanogen, argon and helium. The hydrocarbons are thought to form in Titan's upper atmosphere in reactions resulting from the breakup of methane by the Sun's ultraviolet light, producing a thick orange smog. Titan spends 95% of its time within Saturn's magnetosphere, which may help shield Titan from the solar wind.