The ringed giant
Saturn
Saturn is the sixth planet from the Sun and the second largest, a gas giant famous for the most spectacular ring system in the Solar System. Through even a small telescope its rings are an unforgettable sight.
Saturn is also the least dense planet — lighter on average than water — and has more known moons than any other planet, including Titan, with its thick atmosphere and methane seas, and Enceladus, which sprays water from a hidden ocean.
Key facts
- Diameter
- 120,536 km9.45× Earth
- Mass
- 5.68 × 10²⁶ kg95× Earth
- Gravity
- 9 m/s²0.92 g
- Mean distance from Sun
- 9.58 AU≈ 1,433 million km
- Length of year
- 29.42 yrEarth days or years
- Length of day
- 10.7 hSunrise to sunrise
- Mean temperature
- -140°CAt the 1-bar level
- Known moons
- 274+As of 2025
- Axial tilt
- 26.7°
1 astronomical unit (AU) is Earth's average distance from the Sun, about 149.6 million km. Values follow the NASA Planetary Fact Sheet; many are averages and vary with how and where they are measured.
Physical characteristics
Saturn is 120,536 km across at the equator, about 9.4 times Earth's diameter, and 95 times Earth's mass. Its fast spin makes it the most flattened planet: its equatorial diameter is about 10% larger than its polar diameter.
With an average density of just 687 kg/m³, Saturn is less dense than water. In the often-quoted image, it would float in a bathtub — if one could be built large enough.
Atmosphere and climate
The atmosphere is mostly hydrogen with some helium. High hazes and ammonia clouds soften its bands into muted golds and creams. Winds near the equator reach about 1,800 km/h.
At Saturn's north pole a six-sided jet stream, the hexagon, has persisted for decades; each of its sides is longer than Earth is wide. Roughly once per Saturn year, a giant white storm erupts and wraps around the planet.
Composition: H₂ 96% · He 3% · traces of CH₄
Internal structure
Layers of hydrogen
Like Jupiter, Saturn has no solid surface. Its gas thickens into liquid hydrogen and, deeper still, metallic hydrogen, which generates its magnetic field.
A diffuse core
Studies of ripples in the rings caused by Saturn's internal vibrations suggest the planet's core is large and diffuse, blending gradually into the layers above.
Moons and rings
Saturn's main rings span roughly 280,000 km — most of the distance from Earth to the Moon — yet are typically only about 10 m thick. They are made almost entirely of water-ice particles ranging from dust to house-sized chunks. Gaps such as the Cassini Division are carved by the gravity of moons. How old the rings are is still debated; some measurements suggest they are only a few hundred million years old.
Saturn has at least 274 known moons, more than any other planet. Titan, larger than Mercury, has a dense nitrogen atmosphere and lakes and seas of liquid methane and ethane. Enceladus, a small icy moon, blasts plumes of water vapour and ice from cracks near its south pole, fed by an ocean beneath its crust.
Orbit and rotation
Saturn orbits at an average of 9.58 AU (about 1.4 billion km) and takes about 29.4 Earth years to go around the Sun.
A day lasts about 10.7 hours, although measuring it precisely is difficult because Saturn's magnetic field is aligned almost exactly with its spin axis. Its 26.7° tilt gives it seasons, and roughly every 15 years the rings line up edge-on to Earth and nearly vanish from view — most recently in 2025.
Exploration and missions
Four spacecraft have visited Saturn, and one long-lived orbiter transformed our understanding of it.
- 1979
Pioneer 11 · NASA
The first spacecraft to fly past Saturn.
- 1980–1981
Voyager 1 & 2 · NASA
Revealed intricate ring structure and Titan's thick atmosphere.
- 2004–2017
Cassini–Huygens · NASA / ESA / ASI
Orbited Saturn for 13 years, discovered Enceladus's plumes and ended with a plunge into the atmosphere. Its Huygens probe landed on Titan in 2005, the most distant landing ever made.
- 2028 (planned)
Dragonfly · NASA
A rotorcraft lander planned to launch in 2028 to fly between sites on Titan.
Surprising facts about Saturn
- Saturn is less dense than water.
- Its rings are vast but, in most places, only about as thick as a building is tall.
- Titan is the only moon with a thick atmosphere, and the only other world known to have stable liquid on its surface.
- Saturn's north pole is crowned by a hexagon-shaped jet stream.
- Every 15 years or so the rings appear to vanish when seen edge-on from Earth.
Saturn compared with Earth
| Property | Saturn | Earth |
|---|---|---|
| Diameter | 120,536 km | 12,756 km |
| Mass (Earth = 1) | 95.1 | 1.000 |
| Gravity | 0.92 g | 1.00 g |
| Day | 10.7 h | 24.0 h |
| Year | 29.42 yr | 365.2 d |
| Mean temperature | -140°C | 15°C |
| Moons | 274 | 1 |