Titan is Saturn’s giant - larger than the planet Mercury - and the only moon with a thick atmosphere, an orange nitrogen haze so opaque that its surface was a mystery until Cassini arrived. Beneath the haze lies astonishingly Earth-like scenery: dunes, river valleys, rain-carved channels and glossy seas near the north pole.
ESA’s Huygens probe touched down here in 2005 - still the most distant landing ever made.
Its polar seas hold liquid methane and ethane; Kraken Mare is larger than the Caspian Sea.
Thick air plus low gravity means a human with strap-on wings could fly under their own power.
A weather cycle without water
Earth’s weather runs on water evaporating, condensing and raining back down. Titan runs the identical cycle at -179 °C with methane in every role: methane clouds, methane drizzle, methane rivers draining into seas of liquid methane and ethane. It is the only world besides Earth known to keep standing liquid on its surface.
Physical characteristics
Diameter
5,150 km
Mass
1.350e+23 kg
Surface gravity
1.35 m/s²
Density
1.88 g/cm³
Rotation period
382.7 h
Tidally locked
Yes
Mean temperature
-179 °C
Geometric albedo
0.2
Atmosphere and composition
Atmosphere
Dense nitrogen with a few percent methane; surface pressure is 1.5× Earth’s - the only thick atmosphere on any moon.
Composition
Water-ice shell over a probable internal water ocean and a rocky core.
Interior structure
Rocky coremodelled
Hydrated silicate rock.
High-pressure icemodelled
Ice compressed into dense crystal forms that sink rather than float.
Water-ammonia oceanmodelled
A buried global ocean, salty and possibly ammonia-rich.
Ice crustmodelled
Beneath the orange haze: ice bedrock, methane rivers and dunes.
How we know: Cassini measured how Titan flexes in Saturn’s tides - far too much for a solid interior. The ocean is inferred from that flex plus the electric field Huygens measured.
Discovery
Discovered by
Christiaan Huygens
Year
1655
How
A telescope he built with his brother Constantijn
Missions
Voyager 1NASA · Flyby probe · 1977 · active
The most distant human-made object, now roughly 25 billion km from the Sun. After historic flybys of Jupiter, Saturn and Titan, Voyager 1 became the first spacecraft to enter interstellar space in 2012.
Cassini orbited Saturn for 13 years, delivering ESA’s Huygens probe to the surface of Titan in January 2005 - the first landing in the outer Solar System. It ended with a deliberate plunge into Saturn in 2017 to protect the potentially habitable moons Enceladus and Titan.