Saturn
Saturn is the sixth planet from the Sun and the second-largest in the solar system after Jupiter. It is most famous for its spectacular rings, which are made of millions of pieces of ice and rock. Saturn is a gas giant with no solid surface. It has at least 146 moons, the most of any planet.
- Position 6th planet second gas giant
- Distance from Sun 1.4 billion km 9.5 AU
- Diameter 116,460 km 9 times wider than Earth
- Day length 10h 42m second-fastest spin
- Year length 29.5 Earth years a long trip round the Sun
- Moons 146+ including giant Titan
Where Saturn sits
Saturn is twice as far from the Sun as Jupiter. It orbits at about 1.4 billion km from the Sun, taking 29.5 Earth years to complete one full circuit. A child born when Saturn was in one position would be nearly 30 years old before Saturn returned to that same spot. Like Jupiter, Saturn is bright enough to see from Earth with the naked eye, but its rings can only be seen with a telescope.
Saturn vs Earth
The ringed planet compared to home
Saturn is 9 times wider than Earth. You could fit about 764 Earths inside it.
Saturn is so light that if you had a bath big enough, Saturn would float in it. It's the only planet less dense than water.
Despite being so much bigger, Saturn's gravity is only about 8% stronger than Earth's because Saturn is so much less dense.
Saturn spins almost as fast as Jupiter. Its rapid rotation flattens the planet noticeably, making it the most squashed of all the planets.
Saturn takes nearly 30 Earth years to go once around the Sun.
Saturn has the most moons of any planet, with new ones discovered most years. The biggest one, Titan, is larger than Mercury.
The rings of Saturn
Saturn is one of four ringed planets (Jupiter, Uranus and Neptune also have rings), but Saturn's are by far the largest and brightest. They stretch out for almost 300,000 km from the planet, far enough to reach the Moon's distance from Earth.
Despite being so wide, the rings are surprisingly thin. In most places they are only approx. 10 metres thick. They're made of billions of pieces of ice and rock, ranging in size from tiny grains of dust to chunks the size of a house.
What makes the rings shine?
The pieces in Saturn's rings are made mostly of water ice, which reflects sunlight brilliantly. That's why they're so bright. There are tiny gaps between the rings, called divisions, the most famous of which is the Cassini Division, a 4,800 km wide gap visible from Earth through a telescope.
Where did the rings come from?
Scientists used to think the rings were as old as Saturn itself, but recent evidence suggests they may be surprisingly young, perhaps only 100 million years old. That's a tiny fraction of Saturn's 4.5-billion-year age. They might have formed when a moon or comet got too close to Saturn and was torn apart by gravity.
The rings might disappear
Saturn's rings are slowly raining down onto the planet at a rate of several tonnes per second. At this rate, they will completely disappear in approx. 100 million years. We are lucky to be alive at a time when we can see them. Other ringed planets like Jupiter, Uranus and Neptune may have once had rings as spectacular as Saturn's, but theirs have already faded away.
The hexagon at the north pole
One of Saturn's strangest features is a giant hexagonal storm at its north pole. The hexagon has six perfectly straight sides, each about as wide as Earth. It has been spinning there for at least 40 years (since the Voyager spacecraft first photographed it in 1981) and nobody knows for sure why it has that geometric shape. Some scientists think it's caused by jet streams of gas spinning at different speeds in concentric circles.
The fastest winds in the solar system
Saturn has some of the fastest winds in the solar system. Equatorial winds can reach 1,800 km/h, around four times faster than the strongest hurricanes on Earth. The winds blow constantly in one direction, day after day, year after year.
Saturn's biggest moons
Titan: a moon with weather
Titan is Saturn's largest moon and the second-largest moon in the solar system (after Jupiter's Ganymede). It's bigger than the planet Mercury. Titan is the only moon known to have a thick atmosphere, made mostly of nitrogen. Its surface has rivers, lakes and seas, but they're not full of water. They're full of liquid methane and ethane, which are gases on Earth but liquids on Titan because of the bitter cold (about −180°C).
In 2005, the European Space Agency's Huygens probe landed on Titan, becoming the most distant landing in the history of space exploration. It survived for approx. 90 minutes and sent back photos of an orange landscape with rounded pebbles of ice.
Enceladus: tiny moon, huge plumes
Enceladus is a small icy moon, only approx. 500 km across, but it's one of the most exciting places in the solar system. The Cassini spacecraft discovered enormous plumes of water erupting from cracks at its south pole. These plumes shoot ice and water vapour hundreds of kilometres up into space. They prove that beneath Enceladus's icy crust there is a global ocean of liquid water, which makes it one of the best places to search for life beyond Earth.
The Cassini mission
Most of what we know about Saturn comes from the NASA-ESA Cassini-Huygens mission. Cassini orbited Saturn for 13 years (2004 to 2017), taking hundreds of thousands of photos of the planet, its rings and its moons. When it finally ran out of fuel, scientists deliberately crashed it into Saturn to make sure it didn't accidentally contaminate any of the moons that might have life.
Could humans visit Saturn?
Saturn itself, like all gas giants, has no surface for humans to stand on. But its moons are another matter. Titan is sometimes considered as a possible future home for human colonies, because it has an atmosphere (so people wouldn't need spacesuits, just oxygen masks) and the air pressure is similar to Earth's. The catch is the temperature: −180°C. People would need extremely good insulation to survive.