Saturn

Getting Started

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Rubric: [[file:Space Exploration Adventure Rubric.doc]], [[file:Space Exploration Adventure Rubric.pdf]]
=SATURN= The origin of the rings of Saturn (and the other jovian planets) is unknown. Though they may have had rings since their formation, the ring systems are not stable and must be regenerated by ongoing processes, perhaps the breakup of larger satellites. The current set of rings may be only a few hundred million years old. Radius Radius approx. approx.Name inner outer width position mass (kg) -- -- - D-Ring 67,000 74,500 7,500 (ring)Guerin Division C-Ring 74,500 92,000 17,500 (ring) 1.1e18Maxwell Division 87,500 88,000 500 (divide)B-Ring 92,000 117,500 25,500 (ring) 2.8e19Cassini Division 115,800 120,600 4,800 (divide)Huygens Gap 117,680 (n/a) 285-440 (subdiv)A-Ring 122,200 136,800 14,600 (ring) 6.2e18Encke Minima 126,430 129,940 3,500 29%-53%Encke Division 133,410 133,740Keeler Gap 136,510 136,550F-Ring 140,210 30-500 (ring)G-Ring 165,800 173,800 8,000 (ring) 1e7?E-Ring 180,000 480,000 300,000 (ring Distance Radius MassSatellite (000 km) (km) (kg) Discoverer Date-  -- --- -- -Pan 134 10 ? Showalter 1990Atlas 138 14 ? Terrile 1980Prometheus 139 46 2.70e17 Collins 1980Pandora 142 46 2.20e17 Collins 1980Epimetheus 151 57 5.60e17 Walker 1980Janus 151 89 2.01e18 Dollfus 1966Mimas 186 196 3.80e19 Herschel 1789Enceladus 238 260 8.40e19 Herschel 1789Tethys 295 530 7.55e20 Cassini 1684Telesto 295 15 ? Reitsema 1980Calypso 295 13 ? Pascu 1980Dione 377 560 1.05e21 Cassini 1684Helene 377 16 ? Laques 1980Rhea 527 765 2.49e21 Cassini 1672Titan 1222 2575 1.35e23 Huygens 1655Hyperion 1481 143 1.77e19 Bond 1848Iapetus 3561 730 1.88e21 Cassini 1671Phoebe 12952 110 4.00e18 Pickering 1898
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 * The three pairs Mimas-Tethys, Enceladus-Dione and Titan-Hyperion interact gravitationally in such a way as to maintain stable relationships between their orbits: the period of Mimas' orbit is exactly half that of Tethys, they are thus said to be in a 1:2 resonance Enceladus-Dione are also 1:2; Titan-Hyperion are in a 3:4 resonance.
 * See Scott Sheppard's site for the latest about recently discovered moons (there are lots).
 * There are 9 more that have been discovered but as yet not named.

Visuals Make sure to include the location of your image; add a caption with this information
 * [[image:http://galenet.galegroup.com/images/itkids/pct/00207445.jpg width="128" height="99" caption=" "Cassini Image of Saturn" (Lushpix/Royalty Free.) Reproduced in Kids InfoBits. Detroit: Gale, 2012. http://galenet.galegroup.com/servlet/KidsInfoBits"]] || [[image:http://galenet.galegroup.com/images/itkids/pct/00207381.jpg width="123" height="86" caption=" "Crater on Saturn" (Lushpix/Royalty Free.) Reproduced in Kids InfoBits. Detroit: Gale, 2012. http://galenet.galegroup.com/servlet/KidsInfoBits"]] || [[image:http://galenet.galegroup.com/images/itkids/pct/00207410.jpg width="118" height="107" caption=""Saturn" (Lushpix/Royalty Free.) Reproduced in Kids InfoBits. Detroit: Gale, 2012. http://galenet.galegroup.com/servlet/KidsInfoBits"]] ||
 * [[image:http://galenet.galegroup.com/images/itkids/pct/00207437.jpg width="130" height="96" caption=" "Cassini Orbits" (Lushpix/Royalty Free.) Reproduced in Kids InfoBits. Detroit: Gale, 2012. http://galenet.galegroup.com/servlet/KidsInfoBits"]] || [[image:http://galenet.galegroup.com/images/itkids/pct/00207906.jpg width="140" height="88" caption=" "Saturn's Rings" (Photodisc/Royalty Free.) Reproduced in Kids InfoBits. Detroit: Gale, 2012. http://galenet.galegroup.com/servlet/KidsInfoBits"]] || [[image:http://galenet.galegroup.com/images/itkids/pct/00207403.jpg width="132" height="118" caption=" "Three Moons" (Lushpix/Royalty Free.) Reproduced in Kids InfoBits. Detroit: Gale, 2012. http://galenet.galegroup.com/servlet/KidsInfoBits"]] ||

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[|orbit]: 1,429,400,000 km (9.54 [|AU]) from [|Sun][|diameter]: 120,536 km (equatorial)[|mass]:5.68e26 kg In Roman mythology agriculture. The associated Greek god, [|Cronus], was the son of Uranus and Gaia and the father of Zeus (Jupiter). Saturn is the root of the English word "Saturday" (see [|Appendix 5]). Saturn has been known since prehistoric times. [|Galileo] was the first to observe it with a telescope in 1610; he noted its odd appearance but was confused by it. Early observations of Saturn were complicated by the fact that the Earth passes through the plane of Saturn's [|rings] every few years as Saturn moves in its orbit. A low [|resolution] image of Saturn therefore changes drastically. It was not until 1659 that [|Christiaan Huygens] correctly inferred the geometry of the rings. Saturn's rings remained unique in the known solar system until 1977 when very faint rings were discovered around [|Uranus] (and shortly thereafter around [|Jupiter] and [|Neptune]). Saturn was first visited by NASA's [|Pioneer 11] in 1979 and later by [|Voyager 1] and [|Voyager 2]. [|Cassini] (a joint NASA / ESA project) arrived on July 1, 2004 and will [|orbit] Saturn for at least four years. Saturn is visibly flattened (oblate) when viewed through a small telescope; its equatorial and polar diameters vary by almost 10% (120,536 km vs. 108,728 km). This is the result of its rapid rotation and fluid state. The other gas planets are also oblate, but not so much so. Saturn is the least dense of the planets; its specific gravity (0.7) is less than that of water. Like Jupiter, Saturn is about 75% hydrogen and 25% helium with traces of water, methane, ammonia and "rock", similar to the composition of the primordial [|Solar Nebula]from which the solar system was formed. Saturn's interior is similar to Jupiter's consisting of a rocky core, a [|liquid metallic hydrogen] layer and a molecular hydrogen layer. Traces of various [|ices] are also present. Saturn's interior is hot (12000 K at the core) and Saturn radiates more energy into space than it receives from the [|Sun]. Most of the extra energy is generated by the [|Kelvin-Helmholtz mechanism] as in Jupiter. But this may not be sufficient to explain Saturn's luminosity; some additional mechanism may be at work, perhaps the "raining out" of helium deep in Saturn's interior. The [|bands] so prominent on Jupiter are much fainter on Saturn. They are also much wider near the equator. Details in the cloud tops are invisible from Earth so it was not until the [|Voyager] encounters that any detail of Saturn's atmospheric circulation could be studied. Saturn also exhibits long-lived ovals (red spot at center of image at right) and other features common on Jupiter. In 1990, [|HST] observed an enormous white cloud near Saturn's equator which was not present during the Voyager encounters; in 1994 another, smaller storm was observed (left). Two prominent rings (A and B) and one faint ring (C) can be seen from the Earth. The gap between the A and B rings is known as the **[|Cassini] division**. The much fainter gap in the outer part of the A ring is known as the **Encke Division** (but this is somewhat of a [|misnomer] since it was very likely never seen by Encke). The [|Voyager] pictures show four additional faint rings. Saturn's rings, unlike the rings of the other planets, are very bright ([|albedo] 0.2 - 0.6). Though they look continuous from the Earth, the rings are actually composed of innumerable small particles each in an independent [|orbit]. They range in size from a centimeter or so to several meters. A few kilometer-sized objects are also likely. Saturn's rings are extraordinarily thin: though they're 250,000 km or more in [|diameter] they're [|less than one kilometer thick]. Despite their impressive appearance, there's really very little material in the rings -- if the rings were compressed into a single body it would be no more than 100 km across. The ring particles seem to be composed primarily of water ice, but they may also include rocky particles with icy coatings. [|Voyager] confirmed the existence of puzzling radial inhomogeneities in the rings called "spokes" which were first reported by amateur astronomers (left). Their nature remains a mystery, but may have something to do with Saturn's magnetic field. Saturn's outermost ring, the F-ring, is a complex structure made up of several smaller rings along which "knots" are visible. Scientists speculate that the knots may be clumps of ring material, or mini moons. The strange braided appearance visible in the Voyager 1 images (right) is not seen in the Voyager 2 images perhaps because [|Voyager 2] imaged regions where the component rings are roughly parallel. They are prominent in the [|Cassini images] which also show some as yet unexplained wispy spiral structures. There are complex tidal [|resonances] between some of Saturn's moons and the ring system: some of the moons, the so-called [|"shepherding satellites"] (i.e. [|Atlas], [|Prometheus] and [|Pandora]) are clearly important in keeping the rings in place; [|Mimas] seems to be responsible for the paucity of material in the [|Cassini] division, which seems to be similar to the [|Kirkwood gaps]in the asteroid belt; [|Pan] is located inside the Encke Division and [|S/2005 S1] is in the center of the Keeler Gap. The whole system is very complex and as yet poorly understood.

The origin of the rings of Saturn (and the other jovian planets) is unknown. Though they may have had rings since their formation, the ring systems are not stable and must be regenerated by ongoing processes, perhaps the breakup of larger satellites. The current set of rings may be only a few hundred million years old.

Like the other jovian planets, Saturn has a significant magnetic field.

When it is in the nighttime sky, Saturn is easily [|visible] to the unaided eye. Though it is not nearly as bright as [|Jupiter], it is easy to identify as a planet because it doesn't "twinkle" like the stars do. The [|rings] and the larger satellites are visible with a small astronomical telescope. There are several [|Web sites] that show the current position of Saturn (and the other planets) in the sky. More detailed and customized charts can be created with a [|planetarium program]. Saturn has 53 named satellites (as of spring 2010):


 * The three pairs Mimas-Tethys, Enceladus-Dione and Titan-Hyperion interact gravitationally in such a way as to maintain stable relationships between their orbits: the period of Mimas' [|orbit] is exactly half that of Tethys, they are thus said to be in a 1:2 [|resonance]; Enceladus-Dione are also 1:2; Titan-Hyperion are in a 3:4 resonance.
 * See [|Scott Sheppard's site] for the latest about recently discovered moons (there are lots).
 * There are 9 more that have been discovered but as yet not named.

Major moons:

Distance Radius MassSatellite (000 km) (km) (kg) Discoverer Date- -- --- -- -[|Pan] 134 10 ? Showalter 1990[|Atlas] 138 14 ? Terrile 1980[|Prometheus] 139 46 2.70e17 Collins 1980[|Pandora] 142 46 2.20e17 Collins 1980[|Epimetheus] 151 57 5.60e17 Walker 1980[|Janus] 151 89 2.01e18 Dollfus 1966[|Mimas] 186 196 3.80e19 [|Herschel] 1789[|Enceladus] 238 260 8.40e19 [|Herschel] 1789[|Tethys] 295 530 7.55e20 [|Cassini] 1684[|Telesto] 295 15 ? Reitsema 1980[|Calypso] 295 13 ? Pascu 1980[|Dione] 377 560 1.05e21 [|Cassini] 1684[|Helene] 377 16 ? Laques 1980[|Rhea] 527 765 2.49e21 [|Cassini] 1672[|Titan] 1222 2575 1.35e23 [|Huygens] 1655[|Hyperion] 1481 143 1.77e19 [|Bond] 1848[|Iapetus] 3561 730 1.88e21 [|Cassini] 1671[|Phoebe] 12952 110 4.00e18 [|Pickering] 1898

Saturn's Rings
Radius Radius approx. approx.Name inner outer width position [|mass] (kg) -- -- - D-Ring 67,000 74,500 7,500 (ring)Guerin Division C-Ring 74,500 92,000 17,500 (ring) 1.1e18Maxwell Division 87,500 88,000 500 (divide)B-Ring 92,000 117,500 25,500 (ring) 2.8e19[|Cassini] Division 115,800 120,600 4,800 (divide)Huygens Gap 117,680 (n/a) 285-440 (subdiv)A-Ring 122,200 136,800 14,600 (ring) 6.2e18Encke Minima 126,430 129,940 3,500 29%-53%Encke Division 133,410 133,740Keeler Gap 136,510 136,550F-Ring 140,210 30-500 (ring)G-Ring 165,800 173,800 8,000 (ring) 1e7?E-Ring 180,000 480,000 300,000 (ring)

Read more about [|Saturn l Saturn facts, pictures and information.] by [|nineplanets.org]