Tethys

/tee"this/, n.
1. Class. Myth. a Titan, a daughter of Uranus and Gaea, the wife of Oceanus and mother of the Oceanids and river gods.
2. Astron. one of the moons of Saturn.
3. Geol. the Mesozoic ocean or seaway of which the Mediterranean Sea is a greatly shrunken remnant.

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 major regular moon of Saturn, remarkable for a fissure that wraps around the greater part of its circumference. It was discovered in 1684 by the Italian-born French astronomer Gian Domenico Cassini (Cassini, Gian Domenico) and named for a Titan in Greek mythology.

       Moons of SaturnTethys has a diameter of 1,060 km (659 miles), and its density of 1.0 grams per cubic cm—the same as that of water—indicates that it is composed essentially of pure water ice. It revolves around Saturn in a prograde, circular orbit at a distance of 294,660 km (183,090 miles), which is within the planet's broad, tenuous E ring. It is involved in an orbital resonance with the nearer moon Mimas such that Tethys completes one 45-hour orbit for every two of Mimas. Tethys rotates synchronously with its orbital period, keeping the same face toward Saturn and the same face forward in its orbit. It is accompanied by two tiny moons, Telesto and Calypso (named for daughters of Titans), that maintain gravitationally stable positions along its orbit, analogous to Jupiter's Trojan asteroids (asteroid). Telesto precedes Tethys by 60°; Calypso follows by 60°. (For comparative data about Tethys, its companions, and other Saturnian satellites, see the table (Moons of Saturn).)

      Tethys's most impressive feature is Ithaca Chasma, a giant crack several kilometres deep that extends along three-quarters of the moon's circumference and accounts for 5–10 percent of its surface. Because the ridges around the feature are heavily cratered, scientists have theorized that the chasm was produced early in the moon's geologic history, when the water that composes its interior froze and expanded. A second notable feature is the crater Odysseus, which measures 400 km (250 miles) across and has a large central peak. The density of impact craters on Tethys is high, suggesting that the surface is ancient. Nevertheless, the surface is highly reflective, especially on Tethys's leading face, which is not typical of geologically old surfaces. Planetary scientists suspect that this distribution of surface brightness is affected by the deposition of micrometre-sized ice particles from Saturn's E ring, in which Tethys is well-embedded. Cited as evidence is the observation that many of the craters on Tethys have bright floors, whereas the craters on Saturn's moon Hyperion, which orbits relatively far from Tethys and the E ring, tend to have dark floors.

William B. Hubbard
 

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Universalium. 2010.

Look at other dictionaries:

  • TÉTHYS — L’idée qu’une ancienne communication marine d’orientation est ouest avait dû séparer des masses continentales aujourd’hui adjacentes (telles l’Inde et l’Asie centrale) a été proposée dès la fin du XIXe siècle, lorsque furent reconnues les… …   Encyclopédie Universelle

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  • Tethys — can refer to:*Tethys (mythology), a Titaness in Greek mythology *Tethys (moon) a natural satellite of Saturn *Tethys Ocean, a Mesozoic era ocean between the continents of Gondwana and Laurasiaee also*Thetis …   Wikipedia

  • Tethys — (auch Thetys) steht für: Tethys (Mythologie), eine Titanin in der griechischen Mythologie Tethys (Mond), einen Saturn Mond Tethys (Ozean), ein Meer im Erdzeitalter des Mesozoikums Siehe auch Thetis Palaeotethys Paratethys …   Deutsch Wikipedia

  • TETHYS — uxor Oceani, Terrae et Caeli filia. Hedsiod. in Theogonia, v. 134. Οὐρανῷ εὐνηθεῖϚα τέκ᾿ Ω᾿κεανὸν βαθυδίνην, Κοῖοντε, χρεῖόν θ᾿, Υ῾περίονά τ᾿, Ι᾿απετόν τε, Θείαν τε Ρ᾿είαν τε, Θέμιν τε, ΜνημοϚύνην τε, Φοίβην τε χρυϚοςέ φανον, Τηθυν´ τ᾿ ἐρατεινην´ …   Hofmann J. Lexicon universale

  • Tethys — Tethys1 [tē′this] n. [L < Gr Tēthys] 1. Gr. Myth. a daughter of Uranus and wife of Oceanus, by whom she is the mother of the Oceanides 2. a satellite of Saturn having long trenchlike valleys and sharing its orbit with other satellites Tethys2… …   English World dictionary

  • Tethys — Te thys, n. [NL., fr. Gr. ? an oyster, or ? a kind of ascidian.] (Zo[ o]l.) A genus of a large naked mollusks having a very large, broad, fringed cephalic disk, and branched dorsal gills. Some of the species become a foot long and are brilliantly …   The Collaborative International Dictionary of English

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  • Tethys [1] — Tethys, (nach der Bezeichnung von E. Sueß) das große Mittelmeer, das sich in der Zeit der obern Jura und der Kreideformation und während der ältern Tertiärzeit von Sumatra und Timor über Tongking, Yünnan zum Himalaja und Pamir, Hindukusch und… …   Meyers Großes Konversations-Lexikon

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