- Diameter: 116,460 km
- Mass: 95 Earths
- Density: 0.687 g/cm3
- Surface Gravity at Cloud Tops: 1.07 g
- Semi-major Axis: 9.58 AU
- Orbital Period: 29 Years
- Rotational Period: 10 Hours
- Axial Tilt: 26.73°
- Average Surface Temperature: -139° C
- Notable Features: Saturn's Rings, Northern Polar Hexagon
- Number of Moons: 62
- Number of Total Missions: 4
The planet sometimes known as the Lord of the Rings.
Saturn is the 6th planet in the Solar System, the second most massive (about 95 Earth masses), and the second highest volume, though it's also the least dense (on average, it is less dense than liquid water). It is made mainly of hydrogen and helium gas, with a possibly rocky core in the center, and additional trace elements. Saturn's atmosphere, though looking bland in most far-away pictures, has intense cyclones and storms, and the second fastest winds in the solar system on average (after Neptune). Thanks to its 10.6 hour rotation, the planet bulges from centrifugal force, making it appear a little squashed.
The surface gravity on Saturn is 1.07 g, which is only 7% stronger than Earth despite being more massive. The reason for this disparity has to do with the planet's very low density. If you could stand on Saturn, it would only be about the equivalent of carrying around a moderately heavy backpack on Earth.
Saturn's orbit isn't perfectly circular; at perihelion, it's barely 9 A.U.note from the Sun, but then it swings out until it's over 10 A.U. away from the Sun at aphelion. One complete orbit takes a hair under 29-and-a-half years.
Saturn's magnetic field is the second largest in the Solar System, and is probably generated by metallic hydrogen in the core of the planet. The plasma within the field primarily comes from the moon Enceladus, which shoots water through geysers in the south pole that is then ionized, while some other material comes from Titan, and a bit from other moons. Energy comes from both the solar wind and from Saturn's rotation, somewhat of a mixture of Jupiter's magnetosphere (where rotation supplies most of the energy), and other planetary magnetospheres (where the solar wind supplies almost all the energy). As with other Solar System bodies with magnetic fields, Saturn has its own aurorae. Despite its size, however, Saturn's magnetic field is actually slightly weaker than Earth's, and as such, contains less-potent Van Allen radiation belts. This actually makes the Saturnian system a much more promising place to colonize than most of Jupiter's moons.
Like the other giant planets, Saturn radiates more energy than it receives from the Sun; three times as much in this case. For Saturn this is because its cold temperatures and lack of density causes the helium in its upper atmosphere to condense into droplets, which then rain into the lower atmosphere, converting potential energy to kinetic energy.
Like Jupiter and Neptune, Saturn has its own iconic storm in the Great White Spot, a massive storm that appears approximately every thirty years and lasts for about one Earth year as Saturn approaches its summer solstice. Changes in the density of Saturn's cloud layers as its northern hemisphere receives extra heat from the Sun kicks up an enormous storm that can have varying width. Sometimes the Great White Spot is an oval, similar to Jupiter's Great Red Spot, and other times the Great White Spot can stretch out until it leaves a trail. In one instance, the Great White Spot's trail crossed almost the entire planet. Another iconic storm is Saturn's Hexagon, which is unique in the Solar System for two reasons: it lies on Saturn's north pole (while no other gas giant has a polar vortex), and its outermost layers are shaped like a perfect hexagon.note
It is very likely that the four terrestrial planets, and by extension humanity, have Saturn to thank for their continued existence. Current theories on solar system formation state that it is typical for large gas giants to migrate inward until they orbit extremely close to their stars, often close enough that a full revolution takes only weeks, or even days. Jupiter most likely would have done the same, destroying everything in its path via gravitational forces, if Saturn had not formed with sufficient mass and in the right position to yank Jupiter back, allowing the inner planets to continue forming. This migration also not only pushed Uranus and Neptune to their current positions, but had them swap positions (Neptune had originally been closer to the Sun than Uranus).
The Moons of Saturn are mostly crater-covered ice and rock balls, but the largest, Titan, has a thick atmosphere (about 1.5x the pressure of Earth's), and has a number of hydrocarbon lakes, erosion channels, rivers, and other surface features. Titan may also have ice volcanoes, or other geologic processes. Another moon, Enceladus, has the previously mentioned water geysers, and possibly an underground liquid water layer. The moons of Saturn also help maintain some of the rings, by providing material through collisions, and gravitationally interacting with the rings to keep them stable.
The rings of Saturn are composed of large numbers of ice and rock fragments, possibly formed from a collision of a moon that than never came back together, or possibly formed from material that was too close to Saturn to form a moon in the first place. These clumps often combine and then split, maintaining and redistributing material throughout the rings. Normally, when particles clump together, their tiny gravity is enough to make them keep accreting more and more material this is how the planets formed in the first place. But the rings are so close to Saturn that the big planet's own gravity prevents this from happening. This magical distance from a large object, within which no gravitationally-held-together satellites can exist, is called the Roche limit.
Scientists still debate the age of the rings, which may be relatively recent (in Solar System terms), or may be almost as old as the Solar System. The most recent (2018) research suggests both the former and that they may be a short-lived (in astronomical terms again) feature of Saturn, that will disappear from the inside to the outside within the next hundred million years.
The ring system actually consists of thousands of individual rings, each orbiting the planet at a slightly different distance. There are gaps where few or no rings exist, created by the gravitational interaction between the rings and the moons. The rings are extremely thin, no more than a kilometer thick from one side to the other and perhaps as thin as ten meters. While a few of the fragments making up the rings are made of rock, almost all of the ring fragments are made of plain old water ice, ranging in size from 10 meters across all the way down to a centimeter across. All these chunks of ice and rock are packed into a relatively tight space, as well; Saturn's rings make for a better Asteroid Thicket than the actual asteroid belt does.
Larger rock/ice balls around 10 km in diameter, called "shepherd moons", orbit along with the rings inside the ring plane. The tiny gravity of these moonlets is thought to keep the rings in line, hence their name.
Because of the density of the rings and Saturn's 27° axial tilt, they block out most of the sunlight from reaching Saturn's northern and southern hemispheres during their respective winter seasons, casting notable ring shadows that can be seen from space. These shadows increase in size until Saturn reaches its solstice periods, where they're at their maximum and cover most of the hemispheres, until they recede and form a very thin line at the equator during its equinox periods. It's presumed that the ring shadows have drastic effects on Saturn's climate, potentially affecting the frequency of storms on the enshrouded hemisphere.
Saturn in fiction
Film - Live-Action
- In Interstellar, the wormhole leading to the Gargantua system is orbiting Saturn. In the Distant Finale, a Ring World Planet named Cooper Station can also be found there.
- In Fantastic Four: Rise of the Silver Surfer, Saturn is a Sacrificial Planet whose rings are destroyed by Gah Lak Tus on its way to devour Earth.
- In the novel (not movie) version of 2001: A Space Odyssey, the monolith on the moon aims an intense radio beam at Saturn. The spacecraft Discovery was initially built to explore Jupiter, but due to this radio signal, the mission is re-routed to Saturn at the last minute.
- Larklight: The Giant Spider First Ones are hiding out in the rings of Saturn, an environment which allows them to spin their webs between the ring particles.
- The protagonist The Divine Comedy briefly stops by Saturn on his travels to leave the universe and commune with God. Unlike the other planets, none of the extra-dimensional spirits visiting the planet sing or smile because the expression of their divine happiness would be intense enough to disintegrate our hero.
- Grant D. Callin's Saturnalia focuses on Saturn and its moons, as a sort of cosmic Treasure Island with colonists and Earthers hunting down alien artifacts.
- No Doubt's 2000 album Return of Saturn was named that because around that time the band members were all around 29 years old one orbit of Saturn.
- Gustav Holst's "Saturn, The Bringer of Old Age" from "The Planets" movement.
- The Atlas: Space albums of Sleeping At Last feature music themed around all the planets; "Saturn" is the most popular of them, with the message of it being that despite everything, The World Is Just Awesome.
- Saturns Pattern is the title of an album and song by Paul Weller and references the Hexagon.
- Deathcore band Rings of Saturn named themselves and modeled their logo after the planet due to all of their songs being themed around space and extraterrestrials.
- Mike Banks' techno album X-102 Rediscovers the Rings of Saturn has many of its songs named after Saturnian moons of features of it as rings.
- In Nebula, the solar system is shown as a group of Anthropomorphic Personifications, with Saturn being a quiet recluse (with some Extreme Doormat tendencies) that Uranus and their other neighbors run roughshod over.