Which moon of Saturn has a thick atmosphere?

Titan is the Saturnian moon with a thick atmosphere. In fact, it is the only moon in the Solar System known to have an atmosphere denser than Earth’s.

Titan’s atmosphere is composed mainly of nitrogen, with methane as the most important secondary gas. Sunlight breaks methane apart high in the atmosphere, producing complex hydrocarbons and a thick orange haze. This haze hides the surface in visible light and gives Titan its distinctive appearance.

The atmosphere supports weather and a methane cycle that resembles Earth’s water cycle. Methane can evaporate, form clouds, fall as rain, and collect in rivers, lakes, and seas near the poles. Titan’s surface temperature is about 94 kelvin, so its rivers and lakes contain liquid hydrocarbons rather than liquid water.

Christiaan Huygens discovered Titan in 1655. The Cassini-Huygens mission later transformed knowledge of the moon, with the Huygens probe landing on Titan in 2005. Titan is sometimes called Earth-like because it has clouds, rain, channels, dunes, and lakes—but its chemistry and extreme cold make it a very different world.