Surface gravityThis article covers the physics of gravitation. See also gravity (disambiguation). Gravitation is the tendency of masses to move toward each other. The first mathematical formulation of the theory of gravitation was made by Sir Isaac Newton and proved ast

0.022 m/s²In physics, acceleration (symbol: a is defined as the rate of change (or time derivative) of velocity. It is thus a vector quantity with dimension length/ time². In SI units, this is metre/second². To accelerate an object is to change its velocity over a

Escape velocityFor the video game title, see Escape Velocity (computer game). In physics, for a given gravitational field and a given position, the escape velocity is the minimum speed an object without propulsion, at that position, needs to have to move away indefinite

0.5 km/s

Rotation periodprograde planet like the Earth, the sidereal day is shorter than the solar day. At time 1, the sun and a certain distant star are both overhead. At time 2, the planet has rotated 360° and the distant star is overhead again (1→2 one sidereal day).

65h 41m 05s
( synchronousIn astronomy, synchronous rotation is a planetological term describing a body orbiting another, where the orbiting body takes as long to rotate on its axis as it does to make one orbit; and therefore always keeps the same hemisphere pointed at the body it)

Axial tiltAxial tilt is an astronomical term regarding the inclination angle of a planet's rotation axis in relation to its orbital plane. It is also called obliquity . A planet whose rotation axis were perpendicular to the orbital plane would have an axial tilt of

0.006°

AlbedoNote: This article discusses the physical or planetological property of albedo. For other usage, see Albedo (disambiguation). The albedo is a measure of reflectivity of a surface or body. It is the ratio of electromagnetic radiation reflected to the amoun

0.55

Surface temperatureTemperature is the physical property of a system which underlies the common notions of "hot" and "cold"; the material with the higher temperature is said to be hotter. General description The formal properties of temperature are studied in thermodynamics.

min	mean	max
	-186° C

Atmosphere

none

Dione ("dye OH nee") is a moon of Saturn discovered by Giovanni Cassini in 1684. It is named after the titan Dione of Greek mythology. It is also designated Saturn IV. There is also an asteroid called 106 Dione.

Cassini named the four moons he discovered ( Tethys, Dione, Rhea and Iapetus) Lodicea Sidera ("the stars of Louis") to honour king Louis XIV. Astronomers fell into the habit of referring to them and Titan as Saturn 1 through Saturn 5. Once Mimas and Enceladus were discovered, in 1789, the numbering scheme was extended to Saturn 7.

The names of all seven satellites of Saturn then known come from John Herschel (son of William Herschel, discoverer of Mimas and Enceladus) in his 1847 publication Results of Astronomical Observations made at the Cape of Good Hope[1], wherein he suggested the names of the Titans, sisters and brothers of Cronos (the Greek Saturn), be used.

The Cassini orbiter is due to perform a flyby of Dione on October 10, 2005.

Physical characteristics

Dione is composed primarily of water ice, but as the densest of Saturn's moons (aside from Titan, whose density is increased by gravitational compression) it must have a considerable fraction of denser material like silicate rock in its interior.

Though somewhat smaller, Dione is otherwise very similar to Rhea. They both have similar compositions, albedo features and varied terrain. Both have dissimilar leading and trailing hemispheres. On the trailing hemisphere of Dione there is a network of bright streaks on a dark background and few visible craters. The streaks overlay the craters, indicating that they are newer. The leading hemisphere is heavily cratered and is uniformly bright. The origin of the bright wispy material is somewhat obscure. Apparently, it is material with a high albedo and is thin enough that it doesn't obscure the surface feature underneath. It might have formed from eruptions along cracks in Dione's surface that fell back to the surface as snow or ash.

Like Callisto, the craters lack the high relief features seen on the Moon and Mercury; this is probably due to slumping of the weak icy crust over geologic time.

It is thought that shortly after its formation Dione was geologically active, with some process such as ice volcanism resurfaced much of Dione and leaving the pattern of streaks over its whole surface. Later, after the internal activity and resurfacing ceased, cratering continued primarily on the leading hemisphere and wiped out the streak patterns there.

Dione's icy surface includes heavily cratered terrain, moderately cratered plains, lightly cratered plains, and streaks of wispy material. The heavily cratered terrain has numerous craters greater than 100 kilometers in diameter. The plains area tends to have craters less than 30 kilometers in diameter. Some of the plains are heavily cratered while others are not. Much of the heavily cratered terrain is located on the trailing hemisphere, with the less cratered plains area existing on the leading hemisphere. This is opposite from what some scientists expected; Shoemaker and Wolfe proposed a cratering model for a tidally locked satellite with the highest cratering rates on the leading hemisphere and the lowest on the trailing hemisphere. This suggests that during the period of heavy bombardment, Dione was tidally locked to Saturn in the opposite orientation. Because Dione is relatively small, an impact causing a 35 kilometer crater could have spun the satellite. Since there are many craters larger than 35 kilometers, Dione could have been repeatedly spun during its early heavy bombardment. The pattern of cratering since then and the bright albedo of the leading side suggests that Dione has remained in its current orientation for several billion years.

Scientists recognise the following types of geological feature on Dione:

Chasmata (chasms)
Lineae (wispy features)
Craters

The moon Helene orbits in Dione's leading Lagrangian point, L₄.

... | Telesto, Tethys, Calypso | Dione, Helene | Rhea | ...

Saturn
Janus' group \| Mimas \| Enceladus \| Tethys \| Dione \| Rhea
Titan \| Hyperion \| Iapetus \| Siarnaq's group \| Phoebe's group
(For other moons, see: Saturn's natural satellites)
see also: Cassini-Huygens

Saturn's moons

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Topics: Dione (moon), Dione Lucas, Dione (mythology)...

DioneDione (pronounced in three syllables) may refer to several things: In Greek mythology, Dione ("divine queen"), in three syllables, was the mother of Aphrodite by Zeus. She was a Titan. Her name is actually a feminine form of Zeus. The name is also used to	Dione (moon)Dione ("dye OH nee") is a moon of Saturn discovered by Giovanni Cassini in 1684. It is named after the titan Dione of Greek mythology. It is also designated Saturn IV. There is also an asteroid called 106 Dione. Cassini named the four moons he discovered	Dione LucasDione Lucas was an English woman who was the first female graduate of Le Cordon Bleu''. Lucas was fundamental in establishing an unprecedented extension of the famous Paris culinary school in London in the 1930s. She worked as a hotel chef in Hamburg befo
Dione (mythology)Dione in Greek mythology is the goddess considered to be the mother of Aphrodite. This name comes from Book V of Homer's Iliad Aphrodite journeyed to Dione's side after she is wounded in battle while protecting her favorite and son Aeneas. In this episode	Dioner NavarroDioner Faviau Navarro (born February 9, 1984 in Caracas, Venezuela is a Major League Baseball catcher and switch-hitter batter who plays for the New York Yankees. The Yankees promoted Navarro from AAA Columbus. Considered to be the best prospect left in t