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Saturn is the sixth planet from the Sun and second-largest planet in the Solar System. It also has the most known moons out of any planet, totaling at 274 moons. Saturn is primarily renowned for its byzantine ring system, which consists of water ice, rock, and dust.[5] Saturn's rings are incredibly thin, as ring particles collide with each other and thus cause the orbits of irregular ring particles to become less inclined.[6]
Like other gas giants, Saturn is primarily composed of hydrogen and helium, the same material that makes up the Sun. However, Saturn is nowhere close to being massive enough to even become a brown dwarf. To begin deuterium fusion, Saturn would need around 38 to 48 times its mass.[7]
Saturn's moon system is distinct when compared to other systems, with it having the most ellipsoidal moons out of any planet, as well as its major moons having unique properties. As an example, Saturn's largest moon, Titan, is one of two moons[8] to possess substantial atmospheres.[9]
Physical Characteristics
Atmosphere
Diagram of Saturn's upper atmosphere.
Saturn's atmosphere is extremely deep, reaching depths of at least 9,000 kilometers, three times deeper than Jupiter's atmosphere,[10], and is around 15% of Saturn's radius. The atmosphere additionally has an incredibly high pressure, with atmospheric pressure levels presumed to exceed 1,000 bar.[4]
The upper atmosphere of Saturn is incredibly hot, reaching temperatures as high as 325ºC.[11] These high heat levels are caused by aurorae at the north and south poles of Saturn, which generate electric currents. Although this electricity is initially deposited at the poles, the winds throughout the entirety of Saturn distribute this heat across the planet, eventually resulting in global high temperatures.[12]
The atmosphere consists of 96.3% hydrogen, 3.25% helium, and 0.45% methane. Trace gases, such as ammonia, water vapor, and hydrogen deuteride and aerosols, such as ice and sulfides, are also present, but at a significantly lower volume.
Interior
Interior of Saturn, drawn to scale.
Beneath Saturn's atmosphere is a layer of molten hydrogen and helium created by the extreme pressures from within the planet. The threshold for the helium to become liquid is not entirely clear, but it is believed to occur when the pressure reaches 1,000 bar, or around 1,000 kilometers deep.[13] Although the transition to liquid hydrogen begins at this depth, the bulk of this liquid hydrogen is likely significantly further down, probably beginning in the lower regions of the atmosphere.
Deep inside Saturn is believed to be a thin "helium rain" region just above the metallic hydrogen in which the extreme pressure and frigidity causes the helium to no longer mix with the hydrogen. Consequently, molten helium begins to slowly rain down on to the metallic hydrogen layer. Because of its effects on the magnetic field's dynamo, it is believed to help stabilize Saturn's magnetic field.[14]
Around halfway into Saturn, the pressure and temperature is so extreme that hydrogen begins to behave like a metal. This layer of hydrogen is thinner than that of Jupiter's. Beneath the layer of metallic hydrogen is a solid core made out of ice, rock, and a nickel-iron alloy.[15]
Great White Spot
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Outbreak of the 1990 Great White Spot—taken by Pic du Midi.
The Great White Spot refers to a storm that forms in Saturn's atmosphere every 20 to 30 years. Despite their infrequent and seemingly random emergences, the Great White Spots always seem to occur in Saturn's north hemisphere during summer. It initially starts off as small ovals, but quickly extends into a large band that engulfs a significant portion of the atmosphere. Cassini—Huygens noticed incredibly low temperatures in the center of these storms, while the outer edges were relatively hot.[16]
How and why they form is not exactly known, but one theory suggests that the storms are a result of ammonia ices that form during an event where hotter gasses travel upward.[17] Another theory claims that the weight of water molecules in Saturn's atmosphere causes the northern hemisphere to become lighter, causing a gradual cooling event that disrupts the convection in the northern hemisphere and causes hotter gasses to leak into the upper atmosphere and cause a storm.[18]
The Great White Spots have only been witnessed a handful of times. Great White Spots that are a part of the cycle include: 1876 by Asaph Hall, 1903 by Edward Barnard, 1933 by Will Hay, 1960 by J.H. Botham, 1990 by Stuart Wilber, and 2010 by the CICLOPS team.
Orbit and Rotation
Saturn, the second outer planet, orbits significantly further than Earth, thus taking a significantly longer time to orbit. Saturn takes around twenty-nine years and six months to orbit the Sun.
Saturn's day is also the second-shortest after Jupiter, due to its status as a gas giant. To complete a single rotation, Saturn takes roughly 10 hours and 39 minutes. Its fast rotation causes it to bulge at the equator. Despite having a longer day to Jupiter, its lower density allows to be more oblate.
Moons
Main Page: Moons of Saturn
Saturn's moon system consists of 274 moons, by far the most out of any planet, having a little under three times more than the second most, Jupiter. Like other systems, its moons are separated into different groups, depending on their direct motion and inclination. Saturn's Norse Group has the most moons out of any moon group in the solar system, with the amount exceeding 100. Saturn's two other outer irregular groups, the Gallic and Inuit groups, also contain large amounts of moons.
Major Moons
Several of Saturn's moons to scale—Pan, Atlas, Telesto, Calypso, and Helene are scaled up by a factor of five. Positions are illustrative.
Saturn's major moons are by far the largest moons in the Saturnian system, them being among some of the larger moons in the solar system, ranging in size from that of large asteroids to larger than Mercury. Depending on whether or not Hyperion is considered, Saturn generally has seven or eight major moons. The major moon system has been thought to be stable from outside influences for billions of years.[19][20]
| Name | Discoverer | Date | Diameter (km)[21] |
|---|---|---|---|
| Mimas | William Herschel | September 1789 | 396.4 |
| Enceladus | William Herschel | August 1789 | 504.2 |
| Tethys | Giovanni Cassini | March 1684 | 1,062.2 |
| Dione | Giovanni Cassini | March 1684 | 1,122.8 |
| Rhea | Giovanni Cassini | December 1672 | 1,527 |
| Titan | Christiaan Huygens | March 1655 | 5,149.52 |
| Hyperion | William Lassell | September 1848 | 270 |
| Iapetus | Giovanni Cassini | October 1671 | 1,468.6 |
Inner Moons
The term "inner moons" is a relatively broad term—but at its strictest definition—refers to all moons of Saturn within the orbit of Mimas. Saturn's inner satellites are defined as small, irregular moons orbiting either just outside or within the ring system. As such, most of these moons tend to be either ring shepherds or moonlets. Saturn has eleven inner moons.
| Name | Discoverer | Date | Diameter (km)[22][23] |
|---|---|---|---|
| S/2009 S 1 | Cassini Imaging Team | July 2009 | 0.6 |
| Pan | Mark Showalter | July 1990 | 28 |
| Daphnis | Cassini Imaging Team | May 2005 | 7.6 |
| Atlas | Richard Terrile | October 1980 | 30.2 |
| Prometheus | Stewart Collins and David Carlson | October 1980 | 86.2 |
| Pandora | Stewart Collins and David Carlson | October 1980 | 81.2 |
| Epimetheus | Stephen Larson and John Fountain | October 1978 | 116.4 |
| Janus | Audouin Dollfus | December 1966 | 178.4 |
| Aegaeon | Cassini Imaging Team | August 2008 | 0.66 |
Trojans
The Saturnian system has four known "trojan moons," meaning they orbit in the Lagrange points of a larger moon in the system. Dione and Tethys both have two trojan moons. The existence of these trojan moons imply that the system has likely been stable for a long time.[19]
| Name | Discoverer | Date | Diameter (km)[23] | Parent Moon | Langrage Point |
|---|---|---|---|---|---|
| Telesto | Brad Smith, Harold Reitsema, Stephen Larson, and John Fountain | April 1980 | 24.8 | Tethys | L4 |
| Calypso | Dan Pascu, P. Kenneth Seidelmann, William Baum, and Douglas Currie | March 1980 | 19.2 | Tethys | L5 |
| Helene | Pierre Laques and Jean Lecacheux | March 1980 | 36 | Dione | L4 |
| Polydeuces | Cassini Imaging Team | October 2004 | 2.6 | Dione | L5 |
Alkyonides
The Alkyonides are three small moons of Saturn located between Mimas and Enceladus that are in an orbital resonance with Mimas, causing them to skip forward and backward in their orbits and creating ring arcs.[24]
| Name | Discoverer | Date | Diameter (km)[23] |
|---|---|---|---|
| Methone | Cassini Imaging Team | June 2004 | 2.9 |
| Anthe | Cassini Imaging Team | May 2007 | 1 |
| Pallene | Cassini Imaging Team | June 2004 | 4.46 |
Outer Irregulars
Saturn has 249 outer irregular moons, divided into three groups—the Gallic, Inuit, and Norse groups. Additionally, the Norse group is divided into three sub-groups—the Phoebe, Skathi, and Narvi groups, the Inuit also being divided into three—Kiviuq, Paaliaq, and Siarnaq. Because of the amount of groups and subgroups in the outer irregulars, only the satellites that are approximately 8 kilometers in diameter or larger will be listed.
| Name | Discoverer | Date | Diameter (km)[23][25][26] | Group | Subgroup |
|---|---|---|---|---|---|
| Phoebe | William Pickering | August 1898 | 213 | Norse | Phoebe |
| Siarnaq | Brett Gladman et al. | September 2000 | 43.2 | Inuit | Siarnaq |
| Albiorix | Matthew Holman et al. | November 2000 | 37 | Gallic | |
| Paaliaq | Brett Gladman et al. | August 2000 | 29 | Inuit | Paaliaq |
| Ymir | Brett Gladman et al. | August 2000 | 19 | Norse | Phoebe |
| Kiviuq | Brett Gladman et al. | August 2000 | 17 | Inuit | Kiviuq |
| Tarvos | John Kavelaars et al. | September 2000 | 15 | Gallic | |
| Ijiraq | Brett Gladman et al. | September 2000 | 13 | Inuit | Kiviuq |
| Erriapus | Brett Gladman et al. | September 2000 | 10 | Gallic | |
| Skathi | Brett Gladman et al. | September 2000 | 8 | Norse | Skathi |
| Hyrrokkin | Scott S. Sheppard et al. | December 2004 | 8 | Norse | Skathi |
| Thrymr | Brett Gladman et al. | September 2000 | 8 | Norse | Phoebe |
| Moons of Saturn | ||
|---|---|---|
| Inner Moons | Ring Moonlets | S/2009 S 1 • Aegaeon |
| Ring Shepherds | Pan • Daphnis • Atlas • Prometheus • Pandora • Epimetheus • Janus | |
| Alkyonides | Methone • Pallene • Anthe | |
| Major Moons and Trojans | Large Moons | Mimas • Enceladus • Tethys • Dione • Rhea • Titan • Hyperion • Iapetus |
| Tethys/Dione Trojans | Tethys Trojans (Telesto • Calypso) Dione Trojans (Helene • Polydeuces) | |
| Inuit | Kiviuq Subgroup | S/2023 S 6 • S/2023 S 1 • S/2019 S 1 • S/2004 S 54 • S/2019 S 22 • S/2019 S 23 • S/2020 S 11 • S/2019 S 25 • Kiviuq • S/2023 S 2 • S/2004 S 55 • S/2005 S 4 • S/2020 S 12 • S/2020 S 1 • Ijiraq • S/2019 S 24 • S/2007 S 10 • S/2019 S 26 • S/2020 S 13 • S/2023 S 7 |
| Paaliaq | Paaliaq | |
| Siarnaq Subgroup | S/2023 S 19 • S/2004 S 31 • S/2023 S 3 • S/2019 S 32 • Tarqeq • S/2019 S 14 • S/2020 S 19 • Siarnaq • S/2005 S 6 • S/2020 S 3 • S/2004 S 58 • S/2006 S 23 • S/2019 S 6 • S/2020 S 5 • S/2023 S 22 | |
| Gallic | Albiorix • S/2020 S 15 • Bebhionn • S/2007 S 8 • S/2004 S 29 • S/2023 S 18 • S/2023 S 17 • S/2019 S 29 • Erriapus • S/2007 S 11 • S/2019 S 31 • Tarvos • S/2020 S 4 • S/2019 S 34 • S/2005 S 7 • S/2006 S 12 • S/2004 S 24 | |
| Norse | Low-inclination | Skathi • S/2020 S 17 • S/2023 S 20 • Hyrrokkin • Narvi • S/2023 S 27 • S/2019 S 37 • Bestla • S/2019 S 11 • S/2023 S 30 • S/2020 S 27 • S/2023 S 46 |
| Kari Subgroup | S/2019 S 28 • S/2006 S 25 • S/2006 S 1 • S/2004 S 45 • S/2023 S 33 • S/2020 S 30 • S/2006 S 3 • Kari • Geirrod • S/2019 S 17 • S/2019 S 19 • S/2019 S 18 • S/2004 S 21 • S/2004 S 36 • S/2023 S 45 • S/2019 S 20 | |
| Mundilfari Subgroup | S/2004 S 56 • S/2023 S 8 • S/2023 S 11 • S/2006 S 21 • S/2023 S 9 • S/2006 S 22 • S/2023 S 10 • S/2023 S 12 • S/2007 S 5 • S/2007 S 7 • S/2004 S 37 • S/2004 S 47 • S/2004 S 40 • S/2020 S 14 • S/2019 S 27 • S/2023 S 13 • S/2019 S 3 • S/2020 S 16 • S/2023 S 14 • S/2023 S 16 • S/2020 S 7 • S/2023 S 15 • S/2023 S 50 • Skoll • S/2020 S 18 • S/2019 S 30 • S/2020 S 2 • S/2023 S 4 • S/2019 S 4 • S/2004 S 41 • S/2004 S 57 • S/2020 S 20 • S/2006 S 24 • S/2004 S 42 • S/2019 S 35 • S/2004 S 13 • S/2007 S 6 • Mundilfari • S/2023 S 21 • S/2020 S 21 • S/2019 S 33 • S/2004 S 43 • S/2006 S 10 • S/2019 S 5 • S/2004 S 59 • S/2023 S 23 • S/2020 S 22 • Gridr • Bergelmir • Jarnsaxa • S/2023 S 24 • S/2006 S 27 • S/2004 S 44 • S/2020 S 23 • Hati • S/2004 S 17 • S/2023 S 25 • S/2004 S 12 • Eggther• S/2006 S 13 • S/2023 S 28 • S/2019 S 36 • S/2007 S 9 • Farbauti • S/2023 S 26 • S/2019 S 9 • S/2023 S 48 • S/2020 S 24 • Aegir • S/2019 S 10 • Beli • S/2020 S 25 • S/2023 S 29 • S/2004 S 61 • S/2019 S 12 • S/2023 S 32 • S/2006 S 14 • Gunnlod • S/2019 S 15 • S/2023 S 31 • S/2020 S 6 • S/2004 S 7 • S/2005 S 5 • S/2023 S 34 • S/2020 S 32 • S/2020 S 26 • S/2006 S 16 • S/2006 S 15 • S/2023 S 38 • S/2023 S 36 • S/2004 S 28 • S/2020 S 29 • S/2020 S 8 • S/2023 S 35 • S/2023 S 49 • S/2023 S 39 • S/2004 S 48 • S/2023 S 40 • Fenrir •S/2004 S 50 • S/2019 S 38 • S/2006 S 17 • S/2004 S 49 • S/2023 S 42 • S/2020 S 28 • Surtur • S/2006 S 18 • S/2020 S 34 • S/2020 S 31 • Loge • S/2004 S 39 • S/2019 S 16 • S/2020 S 36 • S/2004 S 53 • S/2020 S 40 • S/2020 S 33 • S/2023 S 43 • Thiazzi • S/2020 S 38 • S/2019 S 42 • S/2019 S 39 • S/2004 S 34 • S/2019 S 40 • S/2020 S 39 • S/2020 S 42 • S/2019 S 41 • Fornjot • S/2023 S 5 • S/2004 S 51 • S/2020 S 10 • S/2020 S 41 • S/2020 S 9 • S/2006 S 29 • S/2019 S 44 • S/2020 S 43 • S/2023 S 44 • S/2019 S 21 • S/2004 S 52 • S/2023 S 47 • S/2019 S 43 • S/2020 S 44
| |
| Phoebe Subgroup | Phoebe • S/2006 S 20 • S/2006 S 9 • S/2007 S 2 • S/2019 S 2 • Greip • S/2006 S 26 • Suttungr • S/2004 S 60 • S/2007 S 3 • S/2006 S 11 • S/2019 S 7 • S/2019 S 8 • Thrymr • S/2004 S 46 • Angrboda • Gerd • S/2019 S 13 • Skrymir • S/2023 S 37 • Alvaldi • S/2023 S 41 • S/2006 S 28 • Ymir • S/2020 S 37 • S/2020 S 35 • S/2006 S 19 • S/2004 S 26 | |
| Other Moons | Hypothetical | Chiron • Themis |
| Unconfirmed Moonlets | S/2004 S 6 • S/2004 S 4 • S/2004 S 3 | |
| Propeller Moonlets | Peggy • Bleroit • Earhart • Santos-Demont | |
History
Observational history
Pre-Telescopic
The earliest observation of Saturn is highly contested, with some claiming that pre-telescopic observations of it date back to 3500 BC. However, the first confirmed observation of Saturn was roughly 1200 BC, in which a text describes that as "Shamash" rises, it approaches the Moon and "two stars."[1] Saturn is not specifically mentioned, but based on the juxtapositions of Saturn and the Moon at the time, it's very likely it was Saturn.[27] In roughly AD 150, Alexandrian astronomer and mathematician Ptolemy developed his geocentric mode and calculated that Saturn's orbit was about thirty years long.
Telescopic
Huygens' sketches of the various perceptions of Saturn between 1610 and 1659.
The telescopic observation of Saturn was in July 1610 by Galileo Galilei. Upon observing Saturn, he initially believed that was "not a single but a composite of three," and he observed that the distance between them was "not greater than a fine obscure thread." In 1612, he noticed that the two bodies were gone, and that the "large star in the middle was alone." In June 1614, he explained that he observed two "miters" in place of two moons he saw four years before, and that there were two particularly obscure spots placed in the middle of them.[28] Galileo's various descriptions of Saturn's rings as "stars," "miters," and "ears" is attributed to the fact that Galileo's telescope was not powerful enough to properly resolve the rings. Until Christiaan Huygens published Systema Saturnium in 1659, astronomers continued to variously describe Saturn's ring system as "handles," "miters," and other terms of the like.
Much later in March 1655, Christiaan Huygens first observed Titan, which he dubbed Saturni Luna, Latin for "Saturn's moon." He estimated that Titan's orbital period was about 15 days and 22½ hours, remarkably close to today's calculations. He also was the first person to correctly identify Saturn's ring system, describing Saturn as "surrounded by a thin flat ring, nowhere touching." In 1671–1672, astronomer Jean-Dominique Cassini discovered two more moons of Saturn—Rhea and Iapetus, and later Tethys and Dione in 1684. He named all four of these moons Sidera Lodoicea, in honor of King Louis XIV.[29] Cassini was also the first person to observe the Cassini Gap in 1675, and suggested that Saturn's rings were made out of thousands of small moonlets.
Saturn as seen in a 1922 magazine.
In 1789, astronomer William Herschel later found Mimas and Enceledaus describing them as being "carried away from their places," essentially confirming the discovery. Johann Franz Encke first observed the Encke Gap in Saturn's rings in 1837, which he described as a "broad variation of brightness" in the A ring. In 1848, William Lassel and George & William Bond independently discovered the moon Hyperion, and mentioned its "particular reddish hue," remarking that it was similar to Iapetus.
Probed exploration
Voyager 2 image of Saturn.
Pioneer 11 was the first unmanned object to perform a flyby of Saturn in 1979. Its flyby's purpose initially was to gauge the safety of the recently-launched Voyager probes passing through Saturn's ring plane. Pioneer 11's flyby resulted in NASA obtaining valuable scientific data, proving that the ring plane was safe to pass through, and confirmed observations made by Stephen Larson and John Fountain regarding Janus and Epimetheus being separate bodies.
Voyager 1 and 2 encounter Saturn in 1980 and 1981, respectively, and discovered six new moons—Atlas, Prometheus, Pandora, Telesto, Calypso, and Helene. Additionally, Voyager 1 discovered the Keeler Gap in Saturn's rings. Because the Voyagers had more advanced instruments and flew by closer, they captured significantly more data about Saturn and its moons than Pioneer 11.
Cassini–Huygens arrived at Saturn in 2004 and discovered many new moons and features about Saturn which were previously unknown. This was due to its especially long mission, lasting until 2017. It also captured many high-quality images of Saturn and its moons, unlike Pioneer 11 or the Voyagers. Cassini–Huygens is regarded as one of the most successful missions done by NASA.
Evolutionary History
There are two main theories that explain the formation of Saturn—the core accretion model, and the disk instability model. Both of these models suggest that Saturn was one of the earliest planets to form. Early in the Solar System's life, material from the Sun's circumstellar disk eventually coalesced into Jupiter and Saturn, and due to their quick and early formation, they immediately dominated the middle solar system.[30]
The core accretion theory suggests that the gas giants gradually formed over time, but this theory is considered obsolete as there are many holes in it. It is believed that if the core accretion theory were real, the gas giants would be on a slow "death march" towards the Sun. The disk instability theory suggests that the gas giants started as premature "clumps" of hydrogen and helium, that rapidly coalesced into planets, potentially within a few millennia.
Ring System
Main Page: Rings of Saturn
Saturn backlit by the Sun, having its faint G and E rings visible. Its rings are labeled.
Saturn's rings are by far the most expansive and complex out of the planets that have them. They stretch as wide as 288,000 kilometers, and hundreds of thousands more if the E ring and Phoebe rings are included. Despite their width, the rings are incredibly thin, and can be only 10 meters high. Some vertical structures in the B ring can reach as tall as 2.5 kilometers, though these are still extremely thin compared to Saturn itself.[31]
Saturn's rings are not one giant ring, but rather five separate rings: the D, C, B, A, and F rings. The rings are not lettered by their distance from Saturn, but rather by the order they were discovered in. Saturn has two other rings—the G and E rings—but these rings lie outside the main ring system, and do not have the same composition as the main rings. The main rings of Saturn are made of various kinds of ice, including water ice, ammonia ice, methane ice, and nitrogen ice.[32] The rings also have small amounts of dust and rock. The G and E rings consist of ejecta from Enceladus's geysers, which are maintained and replenished by both Mimas and Enceladus, respectively.
Saturn's rings are believed to have originated from the destruction of a moon—called Chrysalis—roughly 100–400 million years ago.[33] The main reason for the destruction of Chrysalis is thought to be the outwards migration of Titan. Chrysalis's interactions with Titan caused Saturn's tilt to increase via its resonance with Neptune. Over time, Chrysalis's orbit eventually destabilized and ended up in the Roche limit, causing it to be torn up into Saturn's current ring system.[34] Some theories suggest that Saturn's rings have been replenished by similar moon destructions over billions of years.[35]
Saturn seen during a Ring Crossing Event.
Because Saturn's rings are so thin, every 13–16 years, a ring plane crossing event occurs. This is when Saturn's rings directly face the Earth, causing them to appear invisible from a small, ground-based telescope.
Saturn's rings also have gaps between them, known simply as "gaps." They are formed by small moonlets, ring shepherds, and resonances from other moons. The Cassini and Roche divisions are extremely large gaps that separate the A and B rings, and A and F rings, respectively.
A list of Saturn's rings and gaps and their distances are listed below:
| Ring/Gap Name | Radius of inner edge (km)[36] | Width (km)[36] |
|---|---|---|
| D | 67,000 | 7,500 |
| C | 74,490 | 17,500 |
| Colombo Gap | 77,800 | 100 |
| Maxwell Gap | 87,500 | 270 |
| Bond Gap | 88,690 | 30 |
| Dawes Gap | 90,200 | 20 |
| B | 91,980 | 25,500 |
| Cassini Division | 117,500 | 25,500 |
| Huygens Gap | 117,680 | 285–440 |
| Herschel Gap | 118,183 | 102 |
| Russell Gap | 118,597 | 33 |
| Jeffreys Gap | 118,931 | 38 |
| Kuiper Gap | 119,403 | 3 |
| Laplace Gap | 119,848 | 238 |
| Bessel Gap | 120,236 | 10 |
| Barnard Gap | 120,305 | 13 |
| A | 122,050 | 14,600 |
| Encke Gap | 133,570 | 325 |
| Keeler Gap | 136,505 | 35 |
| Roche Division | 136,770 | 2,600 |
| F | 140,224 | 30–500 |
| G | 166,000 | 8,000 |
| E | 180,000 | 300,000 |
| Phoebe | 7,772,240[37] | 4,766,000[37] |
Exploration
Pioneer 11
Artist's depiction of Pioneer 11's Saturn flyby.
Pioneer 10 and 11 were both intended to do flyby missions of Jupiter, with Pioneer 11 specifically intended to simply do verifications and follow-ups on information collected by Pioneer 10. Additionally, Pioneer 10 and 11 were essentially used as pathfinders to ensure that the Voyagers would not be damaged by the asteroid belt and Jupiter's ionizing radiation. However, some time during Pioneer 11's flyby of Jupiter, it was realized that Jupiter's gravity could be used to slingshot Pioneer 11 towards Saturn. This idea was formally approved in early 1975.[38]
While en route to Saturn, several of Pioneer 11's instruments failed, but the mission wasn't entirely jeopardized. The flyby of Saturn in 1979 was intended to be another pathfinding mission, with Pioneer 11 being used to pass through the ring plane, as Voyager 2 was intended to pass through the G and F rings of Saturn.[39]
Pioneer 11 gave a preliminary analysis on Saturn, and took several images and observed its ring system and magnetic field, but didn't gather as much information as the Voyagers. This was because it was designed as a pathfinder spacecraft—the Voyagers were more scientifically advanced. During its flyby, it had a close encounter and near collision with the moon Epimetheus.
Voyager 1 & 2
Mosaic of Saturn and its moons compiled from Voyager images.
The Voyager spacecraft were launched a few months apart in 1977, and both arrived at Jupiter—also a few months apart—in 1979. The primary goal of the Voyagers were to give detailed information about Saturn and its moons—particularly Titan—and reassessing data provided by Pioneer 11.
Voyager 1 was the first of the voyagers to arrive at Saturn, arriving within its hill sphere in November 12, 1980. Its flyby of Saturn was optimized specifically for a close flyby of the moon Titan, particularly due to it being the only known moon at the time to have an atmosphere. During its flyby of Titan, it calculated the atmosphere's air pressure, the surface temperature, the composition of the atmosphere (mostly nitrogenous), its hydrocarbon lakes, and its size. Voyager 1 had also discovered five new moons at the time, most of them being ring shepherds. It also noticed a sharp color difference at Titan's poles, which was correctly assumed to be due to seasonal changes.[40]
Voyager 2 subsequently entered Saturn's hill sphere in August 25, 1981, and had a significantly closer encounter with Saturn than Voyager 1, its predecessor. It observed features known as "spokes," which are long, sharp-appearing figures that can be seen in Saturn's ring system during what is known as "spoke season."[41] Additionally, it observed Saturn's inner majors moons, such as Mimas, Enceladus, and Tethys, in greater detail than Voyager 1.
Cassini–Huygens
Saturn as seen by Cassini during its extended Equinox mission in 2008.
Cassini–Huygens was initially launched in 1997, and took its first image of Saturn on October 21, 2002. It entered Saturn's orbit on July 1, 2004. Its objective was to perform flybys of several of Saturn's moons, observe Saturn's storms, its rings, atmosphere, and so on. Its first moon flyby was of Phoebe on June 11, 2004. Phoebe was the only one of Saturn's outer moons to be encountered in the Cassini mission.
A major highlight of the mission was the Huygens landing on Titan, which occurred on January 14, 2005. After a two hour descent, it landed on Titan's surface and provided images. It is to date the only time a spacecraft landed on a body in the outer solar system. Cassini had also performed many flybys of Titan, being able to map its entire surface through its thick orange haze.
Cassini performed flybys of many moons in the Saturnian system during its 13 year-long mission, including the moons Pandora, Anthe, Pallene, Pan, Epimetheus, Janus, Prometheus, Helene, Telesto, Calypso, Polydeuces. Mimas, Enceladus, Tethys, Dione, Rhea, Titan, Iapetus, and Phoebe. It also observed many weather patterns and phenomena associated with Saturn itself. The amount of data gathered by Cassini is the main reason why Cassini is often regarded as one of the most successful NASA missions.
Eventually, as fuel dwindled, a final flyby of Titan occurred on April 22, 2017, before going through a series of dips between Saturn and its ring system to safely crash into Saturn. On September 15, 2017, Cassini eventually descended into Saturn's atmosphere.
Gallery
See Also
References and Footnotes
- ↑ 1.0 1.1 Mesopotamian Astrology, written by Ulla Koch-Westenholz, 1995, page 123.
- ↑ Saturn, author and date unknown.
- ↑ Latitudinal variations in Saturn's ionosphere: Cassini measurements and model comparisons, written by Luke Moore et al., 2010.
- ↑ 4.0 4.1 4.2 4.3 Saturn Fact Sheet, written by David R. Williams, last updated 2025.
- ↑ What are Saturn's rings made of?, written by Stephanie Watson, 2023.
- ↑ The Rings of Saturn, written by Dr. David G. Simpson, date unknown.
- ↑ THE DEUTERIUM-BURNING MASS LIMIT FOR BROWN DWARFS AND GIANT PLANETS, written by David S. Spiegel et al., 2011.
- ↑ The other one is Triton.
- ↑ Constraints on the evolution of the Triton atmosphere from occultations: 1989–2022, written by B. Sicardy et al., 2023.
- ↑ Saturn’s Atmosphere Proves Deep, Its Rings Young author unknown, 2019.
- ↑ Saturn’s auroras may explain the planet’s weirdly hot upper atmosphere, written by Lisa Grossman, 2020.
- ↑ Data From NASA’s Cassini May Explain Saturn’s Atmospheric Mystery, written by Naomi Hartono, 2020.
- ↑ Saturn, written by Mark Marley et al., 2025.
- ↑ HELIUM RAIN INSIDE SATURN MIGHT SHAPE ITS MAGNETIC FIELD, written by Jeff Hecht, 2021.
- ↑ Gas Giant Interiors: 2003, author unknown, 2003.
- ↑ Taking the Temperature of a Saturn Storm, author unknown, 2011.
- ↑ Hubble Observes A New Saturn Storm, author unknown, 1994.
- ↑ Explaining Saturn's Great White Spots, written by Kathy Svitil, 2015.
- ↑ 19.0 19.1 Tethys - NASA Science, unknown author, 2024.
- ↑ Whether Saturn's rings are young or old, its moons may be as ancient as the planet itself, written by Matt Williams, 2023.
- ↑ The Orbits of the Main Saturnian Satellites, the Saturnian System Gravity Field, and the Orientation of Saturn's Pole, written by Robert A. Jacobson, 2022.
- ↑ FREE UNSTABLE MODES AND MASSIVE BODIES IN SATURN’S OUTER B RING, written by J. N. Spitale and C. C. Porco, 2010.
- ↑ 23.0 23.1 23.2 23.3 The inner small satellites of Saturn: A variety of worlds, written by P. C. Thomas et al., 2013.
- ↑ Cassini Images Ring Arcs Among Saturn's Moons, author unknown, 2008.
- ↑ New ephemerides of outer planetary satellites, written by N. V. Emelyanov et al., 2022.
- ↑ CASSINI OBSERVATIONS OF SATURN'S IRREGULAR MOONS written by Tilmann Denk et al., 2019.
- ↑ Saturn as the “Sun of Night” in Ancient Near Eastern Tradition, written by Marinus Anthony van der Sluijs and Peter James, 2013.
- ↑ Galileo's Work on Saturn's Rings, written by E. A. Partridge & H. C. Whitaker, 1896, pages 408–414.
- ↑ Tethys - NASA Science, written by Lauren Lindsey, last updated 2024.
- ↑ How Was Saturn Formed?, written by Nola Taylor Tillman, 2012.
- ↑ The Tallest Peaks, author unknown, 2010.
- ↑ 'Surprising’ chemical complexity of Saturn’s rings is changing the planet’s upper atmosphere, written by Brendan M. Lynch, 2018.
- ↑ Micrometeoroid infall onto Saturn’s rings constrains their age to no more than a few hundred million years, written by Sascha Kempf et al., 2023.
- ↑ Loss of a satellite could explain Saturn’s obliquity and young rings, written by Jack Wisdom et al., 2022.
- ↑ Saturn’s Rings May Be Old Timers, author unknown, 2007.
- ↑ 36.0 36.1 Ring and Ring Gap Nomenclature, Planetary Names, date unknown.
- ↑ 37.0 37.1 The ring system, written by Mark Marley et al., 2025.
- ↑ 40 Years Ago: Pioneer 11 First to Explore Saturn, written by John Uri, 2019.
- ↑ 38 years after Pioneer 11, Cassini enters final 2 weeks of Saturnian mission, written by Chris Gebhardt, 2017.
- ↑ Titan Exploration, written by Amanda Barnett, 2025.
- ↑ Ring Spokes, author unknown, 2004.
| The Planets and Dwarf Planets | |
|---|---|
| Planets | |
| Inner: (Mercury • Venus • Earth • Mars) Outer: (Jupiter • Saturn • Uranus • Neptune) | |
| Dwarf Planets (and candidates) | |
| Ceres • Pluto • Haumea • Makemake • Quaoar • Orcus • Eris • Gonggong • Sedna | |