The D ring:
Width: 7,600 km
Distance: 66,900-74,510 km
Thickness: unknown
Density: unknown
Eccentricity: unknown
Total mass: unknown
The D ring is the closest to Saturn of any of the known rings, and is fainter than any of the other main rings. This ring, unlike the others, has no distinct structure except for a series of faint, evenly-spaced ringlets. The brighter of the rings are designated D68, D72, and D73. In 1980, the rings orbited at 67,000, 72,000, and 73,000 kilometers respectively. However, later images by the Cassini space probe showed that D72 had moved 200 kilometers closer to Saturn and had grown dimmer. It's expected that the disruption was caused by a comet pushing the ring slightly out of its orbit, and it is currently reverting back into its original orbit.
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| The D ring, showing the evenly-spaced ringlets. Credit: NASA/JPL/Space Science Institute |
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| The D ring in 1980 (bottom) and 2005 (top) showing the inward travel of the D72 ringlet (2nd from left) Credit: NASA/JPL/Space Science Institute |
Width: 17,342 km
Distance: 74,658-92,000 km
Thickness: 5 meters
Density: varies from 1.4 g/cm2 (inner edge) to 17 (titan ringlet)
Eccentricity: unknown
Total mass: 1.1 Pentillion kg.
The C ring is slightly brighter and larger than the D ring, and has more detail in it than the D ring. The main structures of it are the Colombo gap, a hole in the ring system, about 77,900 kilometers from Saturn, and, inside that gap, the Titan ringlet. These two structures are likely caused by an orbital resonance with Titan. The ringlet is slightly eccentric, with the end furthest from the Sun pointing towards Titan's location. Another, weirder gap in the rings is the Maxwell gap. This gap is about 87,500 kilometes out, and has a smaller ringlet within it. This ringlet is called the Maxwell ringlet for lack of a better name. While this ringlet has wave-like structures, implying a shepard moon orbiting near it, there has been no moon discovered to create the Maxwell gap and ringlet.
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| The C ring, showing the Titan gap (right) with the ringlet visible on the outer edge of it. The Maxwell gap is visisble at the upper right corner as a dim area outside the broad, fairly bright ring, and then a small, bright ringlet. |
The B ring:
Width: 25,500 km
Distance: 92,000-117,580 km
Thickness: 5-10 meters
Density: 20-100 g/cm2
Eccentricity: unknown
Total mass: 28 Pentillion kg
Of all of Saturn's rings, the B ring is definitely the brightest, largest, and most massive of any of them. It seems to have a wide range of ringlets and objects, but no apparent gaps. While most of the ring is flat, however, the outer edge of the ring also appears to be full of small moonlets up to 2.5 km across. Among other formations, the ring also appears to have small clouds of dust, called 'spokes, in it. This is confusing, because previously the rings had been believed to be created by gravity alone, but the regular appearance of the spokes doesn't seem to follow the theory. The current explanation for them is that small electric charges in them pushes them slightly away from the rest of the ring (similar to how 2 magnets will repel each other if faced the same direction against each other.) The rings also appear to be seasonal, appearing during Saturn's 'spring' and 'fall' equinoxes. While the ring doesn't appear to have any shepard moons, in 2009, while analyzing Cassini data, scientists found a moonlet about 400 meters in diameter. The moon was given the designation S/2009 S1.
The Cassini Division
Width: 4,700 km
Distance: 117,580-122,170 km
Thickness: 20 meters
Density: 18-20 g/cm2
Eccentricity: unknown
Total mass: unknown, probably around 0.05-0.3 pentillion kg
While Saturn's B ring is the most massive, on the contrary, the Cassini Division, which is right outside it, is the most noticeable gap in the system. It is named after Giovanni Domenico Cassini, who discovered it in 1675. With only a 90x magnification, it's possible to view the gap. However, at the time, the gap appeared to be completely devoid of matter, but today's telescopes show it to have some dust inside of it, including a couple of real 'gaps'. The more notable of these is the Huygens gap, at around 117,700 kilometers out. It marks the beginning of the Cassini division, and appears to be caused by a 2:1 resonance with Mimas (it orbits twice for every orbit of Mimas.) Inside of this gap is a small ringlet called (surprise surprise) the Huygens ringlet. The smaller of these gaps is located at about 121,000 kilometers from Saturn, and is called the Laplace gap. This gap doesn't appear to have any direct cause for its formation except that it is near the outer boundary of the ring. It, unlike most other gaps, doesn't have any known ringlet within it and has no moon causing it to be there, leaving astronomers puzzled.
The A ring:Total mass: 28 Pentillion kg
Of all of Saturn's rings, the B ring is definitely the brightest, largest, and most massive of any of them. It seems to have a wide range of ringlets and objects, but no apparent gaps. While most of the ring is flat, however, the outer edge of the ring also appears to be full of small moonlets up to 2.5 km across. Among other formations, the ring also appears to have small clouds of dust, called 'spokes, in it. This is confusing, because previously the rings had been believed to be created by gravity alone, but the regular appearance of the spokes doesn't seem to follow the theory. The current explanation for them is that small electric charges in them pushes them slightly away from the rest of the ring (similar to how 2 magnets will repel each other if faced the same direction against each other.) The rings also appear to be seasonal, appearing during Saturn's 'spring' and 'fall' equinoxes. While the ring doesn't appear to have any shepard moons, in 2009, while analyzing Cassini data, scientists found a moonlet about 400 meters in diameter. The moon was given the designation S/2009 S1.
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| The outer B ring, showing the small moonlets embedded in it. Credit: NASA/JPL/Space Science Institute |
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| S/2009 S1's discovery image. Note the long shadow despite the fairly small moon to cast it. Credit: NASA/JPL |
Width: 4,700 km
Distance: 117,580-122,170 km
Thickness: 20 meters
Density: 18-20 g/cm2
Eccentricity: unknown
Total mass: unknown, probably around 0.05-0.3 pentillion kg
While Saturn's B ring is the most massive, on the contrary, the Cassini Division, which is right outside it, is the most noticeable gap in the system. It is named after Giovanni Domenico Cassini, who discovered it in 1675. With only a 90x magnification, it's possible to view the gap. However, at the time, the gap appeared to be completely devoid of matter, but today's telescopes show it to have some dust inside of it, including a couple of real 'gaps'. The more notable of these is the Huygens gap, at around 117,700 kilometers out. It marks the beginning of the Cassini division, and appears to be caused by a 2:1 resonance with Mimas (it orbits twice for every orbit of Mimas.) Inside of this gap is a small ringlet called (surprise surprise) the Huygens ringlet. The smaller of these gaps is located at about 121,000 kilometers from Saturn, and is called the Laplace gap. This gap doesn't appear to have any direct cause for its formation except that it is near the outer boundary of the ring. It, unlike most other gaps, doesn't have any known ringlet within it and has no moon causing it to be there, leaving astronomers puzzled.
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| The Cassini Division is visible at the center of this image, with the Huygens gap visible to the right, and the ringlet on the outer edge of it. The Laplace gap is also visible near the outer edge of the division, showing the obvious lack of a ringlet within it. Credit: NASA/JPL/Space Science Institute |
Width: 14,600 km
Distance: 122,170-136,775
Thickness: 10-30 meters
Density: 30-40 g/cm2
Eccentricity: unknown
Total mass: 6.2 pentillion kg
The A ring marks the end of the popular, bright group of Saturn's rings. The ring is also the largest of the main rings. While the ring is mostly devoid of structure in the form of bright and dark rings, it still contains a few gaps and ringlets. The most notable is the Encke gap. This gap, about 133,590 kilometers from Saturn, is the closest ring to Saturn that is caused by a moon in its orbit, which was discovered in 1990. This moon, named Pan, orbits the closest of any 'moon' of Saturn (not including the moonlet S/2009 S1.) Further out, near the outer boundary of the ring, is the Keeler gap. This gap is much smaller than the Encke gap, only about 1/6th the size. This gap is caused by the moon Daphnis which is about 1/4th the size of Pan. Both of these gaps appear to have small, disturbed ringlets within them probably caused by tidal interactions with the moons in them. Other than these two main moons, hundreds of moonlets have been discovered in the ring. These are only a few hundred meters large, and are only seen from their effects on the ring around them. The most-studied of these has the unofficial name "Bleriot".
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| The Encke Gap is visible, showing a small ringlet with 'knots' caused by previous gravitational interactions with Pan. Credit: NASA/JPL/Space Science Institute |
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| The Keeler Gap with Daphnis in it, showing 'waves' caused by its interaction with the rings. The shadows give a general impression of height relative to the moon itself. Credit: NASA/JPL/Space Science Institute |
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| The Moonlet Bleriot is visible at center bottom in this image, causing small waves in the ring around it, and a partial ring around its orbit. Credit: NASA |
Width: 2,600 km
Distance: 136,775-139,380 km
The Roche Division marks the 'end' to Saturn's main ring system, and is a gap of low-density material between the A and F rings. Around this distance, completely coincidentally, is the Roche Limit. This is the distance from a parent body (in this case Saturn) where a moon of a reasonable size is able to accrete from small particles. The reason the rings drop off significantly here is because most of the rings further out have accreted into small moons already. Anyways, this division is probably caused by the moon Atlas. This moon, about 40*35*19 kilometers across, orbits near the center of this division. It, along with sweeping material out of this area, also forms the F ring. Prometheus, a moon much larger than Atlas, also contributes to the Roche Division, but in an opposite way. This moon pulls material out of the F ring and into the Roche Division. This helps keep the division from being completely devoid of particles, but rather simply a low-density area. Other small moonlets also appear to contribute to it a bit, such as R/2004 S1 and R/2004 S2.
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| The Roche Division and Atlas are visible here, along with the F ring and the Encke and Keeler gaps. Credit: NASA |
Width: 30-500 km
Distance: 140,180 km
Thickness: unknown
Density: unknown
Eccentricity: 0.0026
Total mass: unknown
Just out of the main ring system orbits a small, faint ring called the F ring. It officially marks the end of Saturn's visible rings and is formed by the shepard moons, Pandora and Prometheus. The ring, despite being small, is the most dynamic ring in the system. This ring is also very irregular because Prometheus passes through the orbit of it, leaving gravitational deviations in it. The main ring seems to consist of 3 ringlets: A large, outer one that is sometimes split apart by Prometheus's gravity, a dimmer, inner one that is often straighter, and a faint once near the center that appears to be a faint 'halo'.
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| A straightened-out composite of the F ring, showing the extreme tidal disturbances in it. Note that the inner ring appears to travel within the main ring about 2/3rd to the right of the image. Credit: NASA/JPL/Space Science Institute |
Width: 5,000 km
Distance: 149,000-154,000 km
While the F ring marks the end to the visible rings, there are several faint rings orbiting out of the main system. The closest of these is the Janus/Epimetheus ring. This ring, named after the moons that orbit in it, is extremely faint and is about midway between the F and G ring. The ring is probably caused by ejecta from impacts on these two moons.
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| Saturn's outer ring system, showing the Janus & Epimetheus ring about midway between the F ring (bright, outer ring) and the G ring (shown) Credit: NASA/JPL/Space Science Institute |
Width: 10,000-12,000 km
Distance: 168,000-175,000 km
Thickness: 100,000 meters (100 kilometers)
Density: unknown
Eccentricity: unknown
Total mass: unknown.
The G ring is the furthest out legitimately 'bright' ring, and orbits between the F and E ring. The outer edge of the ring is only 10-20,000 kilometers away from the moon Mimas, which likely formed it. Aegaeon, another moon orbiting within the ring itself, is likely formed by the ring, and not vice versa, accreting out of the ring's faint disk.
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| The central G ring, with Aegaeon (bright dot) orbiting within the brightest segment. The image was taken over 10 minutes. Credit: NASA/JPL/Space Science Institute |
Width: unknown, probably small.
Distance: 194,230 kilometers
Caused by the moon Methone, the Methone Ring arc appears to be caused by collisions with the moon Methone, which explains why it's not very bright (see image below).
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| Image of Methone, showing blatant, obvious lack of impact craters. Credit: NASA/JPL-Caltech/Space Science Institute |
Width: unknown
Distance: 197,665 kilometers
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| The Anthe Ring arc is visible, with Anthe being the bright 'star' near the end of it. |
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| The discovery of Anthe (red square). Note how Mimas appears significantly brighter than the rest of the moons. Credit: NASA/JPL/Space Science Institute |
Pallene ring:
Width: 2,500 km
Distance: 211,000-213,500 km
This ring is the largest of the lunar rings of Saturn, and is formed by the moon Pallene, which is fairly small, but has many impacts on it, forming the large ring. The ring is about as bright as the Janus/Epimetheus ring.
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| The moon Pallene. Credit: NASA/JPL/Space Science Institute |
Width: 302,000 km
Distamce: 181,000-483,000 km
Thickness: 10,000,000 meters (10,000 kilometers)
Density: very low
Eccentricity: unknown
Total mass: unknown
The 2nd outermost of the known rings, and the faintest of the lettered ones, the E ring is one of the dimmest and largest rings of Saturn. The ring begins near Mimas's orbit and ends at that of Rhea, making it span an enormous distance and encompassing everything further than the F ring. Most of the material of the ring seems to come from geysers on Enceladus, which later spreads out around Saturn and occasionally falls to form a blanket on other moons like Tethys, Telesto, Calypso, Helene, and Polydeuces.
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| The E ring, showing Enceladus's silhouette and its effects on the ring. The bright dot directly below it is a geyser erupting near its south pole. Credit: NASA/JPL/Space Science Institute |
Width: 9,000,000 km
Distance: 4,000,000->13,000,000 km
Thickness: 2,300,000 km
In 2009, after the Cassini and Voyager probes had finished finding new rings, scientists searching through Spitzer data found a huge ring around the orbit of Phoebe that, if visible from Earth, would be the size of 2 moons. The ring is probably formed by impacts with Phoebe, which doesn't seem unlikely considering Phoebe's extremely cratered surface. The ring, while orbiting Saturn, orbits Saturn on an angle of 27 degrees. The ring likely migrates inwards over time, eventually falling onto Saturn's outer moons, like Iapetus.
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| The Phoebe Ring in infrared, comparing the size of Saturn to its extent. Credit: NASA/ESA/STScl/AURA |
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| Image of Phoebe, showing heavily-cratered surface. Credit: NASA/JPL/Space Science Institute |
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