What is the largest moon of Saturn?

Titan is the largest moon of Saturn. It is also the second-largest moon in the Solar System, behind Jupiter’s Ganymede, and is larger in diameter than the planet Mercury, although Mercury is much more massive because it contains a denser rocky and metallic interior.

Dutch astronomer Christiaan Huygens discovered Titan in 1655. For centuries, its surface remained hidden beneath a thick orange haze. The Cassini-Huygens mission transformed our understanding of Titan after arriving at Saturn in 2004; its Huygens probe landed on Titan in 2005, the first spacecraft landing in the outer Solar System.

Titan is especially unusual because it has a dense atmosphere, composed mainly of nitrogen, and stable liquid lakes and seas on its surface. However, those liquids are methane and ethane rather than water. Titan’s landscape includes channels, dunes, clouds, and weather driven by a methane cycle that resembles Earth’s water cycle.

The main mix-up is with Ganymede, which is larger overall. Titan is Saturn’s largest moon, while Ganymede is the largest moon of any planet.