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Mimas is a moon of Saturn which was discovered in 1789 by William Herschel.[1] It is named after Mimas, a son of Gaia in Greek mythology, and is also designated Saturn I.

With a diameter of 396 kilometres (Template:Convert/round mi) it is the smallest astronomical body that is known to be rounded in shape because of self-gravitation.


Mimas was discovered by the astronomer William Herschel on 17 September 1789. He recorded his discovery as follows: "The great light of my forty-foot telescope was so useful that on the 17th of September, 1789, I remarked the seventh satellite, then situated at its greatest western elongation."[2]


Mimas is named after one of the Giants in Greek mythology, Mimas. The names of all seven then-known satellites of Saturn, including Mimas, were suggested by William Herschel's son John in his 1847 publication Results of Astronomical Observations made at the Cape of Good Hope.[3][4] He named them after Titans specifically because Saturn (the Roman equivalent of Cronus in Greek mythology), was the leader of the Titans and ruler of the world for some time.

The adjectival form of Mimas is Mimantean or Mimantian.[5][6]

Physical characteristicsEdit


PIA06256 Mimas full view

Cassini view of Mimas's trailing hemisphere, showing craters up to 6 km deep and 1-km-deep chasmata (grooves). The large crater near center is Morgan; Arthur is close to the lower right limb. Pelion Chasma is faintly visible as a horizontal trough left of Arthur and below Morgan.

The surface area of Mimas is slightly less than the land area of Spain. The low density of Mimas, 1.15 g/cm³, indicates that it is composed mostly of water ice with only a small amount of rock. Due to the tidal forces acting on it, Mimas is noticeably prolate; its longest axis is about 10% longer than the shortest. The ellipsoidal shape of Mimas is especially noticeable in some recent images from the Cassini probe.

Mimas's most distinctive feature is a giant impact crater 130 kilometres (Template:Convert/round mi) across, named Herschel after the discoverer of Mimas. Herschel's diameter is almost a third of Mimas's own diameter; its walls are approximately 5 kilometres (Template:Convert/round mi) high, parts of its floor measure 10 kilometres (Template:Convert/round mi) deep, and its central peak rises 6 kilometres (Template:Convert/round mi) above the crater floor. If there were a crater of an equivalent scale on Earth (in relative size) it would be over 4,000 kilometres (Template:Convert/round mi) in diameter, wider than Australia. The impact that made this crater must have nearly shattered Mimas: fractures can be seen on the opposite side of Mimas that may have been created by shock waves from the impact travelling through Mimas's body.[7]

The Mimantean surface is saturated with smaller impact craters, but no others are anywhere near the size of Herschel. Although Mimas is heavily cratered, the cratering is not uniform. Most of the surface is covered with craters larger than 40 kilometres (Template:Convert/round mi) in diameter, but in the south polar region, there are generally no craters larger than 20 kilometres (Template:Convert/round mi) in diameter.

Three types of geological features are officially recognized on Mimas: craters, chasmata (chasms) and catenae (crater chains).

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Orbital resonancesEdit

A number of features in Saturn's rings are related to resonances with Mimas. Mimas is responsible for clearing the material from the Cassini Division, the gap between Saturn's two widest rings, the A Ring and B Ring. Particles in the Huygens Gap at the inner edge of the Cassini division are in a 2:1 resonance with Mimas. They orbit twice for each orbit of Mimas. The repeated pulls by Mimas on the Cassini division particles, always in the same direction in space, force them into new orbits outside the gap. The boundary between the C and B ring is in a 3:1 resonance with Mimas. Recently, the G Ring was found to be in a 7:6 co-rotation eccentricity resonance[Clarification needed] with Mimas; the ring's inner edge is about 15,000 kilometres (Template:Convert/round mi) inside Mimas's orbit.[citation needed]

Mimas is also in a 2:1 mean-motion resonance with the larger moon Tethys, and in a 2:3 resonance with the outer F Ring shepherd moonlet, Pandora.


Pioneer 11 flew by Saturn in 1979, and its closest approach to Mimas was 104,263 km on September 1, 1979.[8] Voyager 1 flew by in 1980, and Voyager 2 in 1981.

Mimas has been imaged several times by the Cassini orbiter, which entered into orbit around Saturn in 2004. A close flyby occurred on February 13, 2010, when Cassini passed by Mimas at 9,500 km (Template:Convert/round mi).

In popular cultureEdit

When seen from certain angles, Mimas resembles the Death Star, a fictional space station known from the 1977 film Star Wars Episode IV: A New Hope, which is said to be roughly 140 kilometres in diameter. Herschel resembles the concave disc of the Death Star's "superlaser". This is coincidental, as the film was made nearly three years before Mimas was resolved well enough to see the crater.[9]

In Star Trek: The Next Generation, Wesley Crusher once beamed to Mimas in an emergency.

In 2010, NASA revealed a temperature map of Mimas, using images obtained by Cassini. The warmest regions, which are along one edge of Mimas, create a shape similar to the video game character Pac-Man, with Herschel Crater assuming the role of an "edible dot" or "power pellet" known from Pac-Man gameplay.[10][11][12]


See alsoEdit


  1. Cite error: Invalid <ref> tag; no text was provided for refs named Herschel1790
  2. Herschel, William Philosophical Transactions of the Royal Society of London, Vol. 80, reported by Template:Cite journal
  3. As reported by William Lassell, Monthly Notices of the Royal Astronomical Society, Vol. 8, No. 3, pp. 42–43 (January 14, 1848)
  4. Template:Cite journal
  5. "Cassini Equinox Mission: Mimas". 2005-08-02. Retrieved 2012-02-26. 
  6. The nt comes from the Latin genitive case Mimantis, from Greek Μῑμάντος; the old form of the name had been Mimans Μίμανς (Liddell and Scott's Greek-English Lexicon)
  7. Template:Cite book
  8. "Pioneer 11 Full Mission Timeline". Retrieved 2012-02-26. 
  9. Young, Kelly (2005-02-11). "Saturn's moon is Death Star's twin". New Scientist. Retrieved 2008-08-21. "Saturn's diminutive moon, Mimas, poses as the Death Star – the planet-destroying space station from the movie Star Wars – in an image recently captured by NASA's Cassini spacecraft." 
  10. Cook, Jia-Rui C. (2010-03-29). "1980s Video Icon Glows on Saturn Moon". NASA. Retrieved 2010-04-02. 
  11. "Bizarre Temperatures on Mimas". NASA. 2010-03-29. Retrieved 2010-04-02. 
  12. "Saturn moon looks like Pac-Man in image taken by Nasa spacecraft". The Daily Telegraph. 2010-03-30. Retrieved 2010-04-02. 

External linksEdit

Template:Moons of Saturn

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