Pandora (moon)

Stewart A. Collins D. Carlson

Pandora (also Saturn XVII) is the sixth and twelfth largest of the 62 known moons of the planet Saturn. The shepherd moon orbits the planet outside the F ring of Saturn's rings.

  • 3.1 size
  • 3.2 Internal structure
  • 3.3 Surface

Discovery and designation

Pandora was discovered in mid-October 1980 by the astronomer Stewart A. Collins and D. Carlson along with Prometheus in evaluations of recordings of the Voyager 1 spacecraft, which passed through the Saturn on 12 November 1980 already before the flyby, the probe.

On 31 October 1980, the discovery of the International Astronomical Union ( IAU) was announced; the moon first received the provisional designation S/1980 S 26 This high numbers resulted from the belief that Saturn had been 27 moons, which later turned out to be an exaggeration. Since many of the " newly discovered " moons were already known, the number was reduced to 16, so the 15 discovered Pandora and Saturn's moon was confirmed. The simultaneous discovery of Prometheus and Atlas discovered shortly after the Roman numbering were awarded according to the ascending order of the distances to Saturn; Pandora was given by the number XVII.

Relatively late, on January 3, 1986 - the same time as Prometheus and the Pluto Charon - the moon was named after Pandora, which was created by the Greek mythology in order to punish the people for the theft of fire, Prometheus. She is the first woman in history and was created at the direction of Zeus by Hephaestus out of clay. To make it more enticing, it is equipped by the gods with many gifts such as beauty, musical talent, skill, curiosity and exuberance. Aphrodite also gives her gracious charm, Athene she decorated with flowers and Hermes, from which it takes its name, gives it a charming language. Zeus gave her named after her " Pandora's box ", which was filled by each of the Olympian gods with a special gift which were fatal except one all. Zeus went down with Pandora to earth and gave it as a gift to the Titans Epimetheus, Pandora against a previous warning whose brother Prometheus also accepted and married. Pandora (or her husband Epimetheus ) opens the box, and the stored therein diseases, plagues vices and vices were let loose on the people. Before even the only positive response - hope - can escape from the bush, it is closed again. So the world is a desolate place until Pandora opens the box again and also hope can in the world. But the golden age in which mankind was spared from work, sickness and death, is finally over.

Since the early Christianity, the story of Pandora is often seen as an allegory of the biblical Fall. Pandora is for seducing Eve and Epimetheus for transmitting seduced Adam.

The name is derived from pan for general, overall, and for doron gift, assembled gift; however, it is traditionally translated as " all-gifted ".

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Orbit

Pandora orbits Saturn on a prograde, nearly perfectly circular orbit at an average distance of 141,720 kilometers (about 2,351 Saturn radii ) from its center, ie 81,452 km above the cloud tops. The orbital eccentricity is 0.0042, the orbit is inclined 0.05 ° relative to the equator of Saturn, that is almost exactly in the equatorial plane of the planet. Due to the low eccentricity of the track varies in distance to Saturn were only about 1190 km.

The orbit of the next inner moon Prometheus is located in the central 2340 km from the orbit of Pandora, the distance of the path of the next outer moons Epimetheus and Janus is an average of 9,690 or 9740 km.

Pandora orbits Saturn in 15 hours, 5 minutes and 2.8 seconds. This is slightly more than the orbital period of Uranus moon Cupid. Pandora needed for a round about 23 minutes longer than the inner neighboring Prometheus.

The moon runs about 1,500 out of 1979 by the space probe Pioneer 11 discovered narrow faint F ring around the planet. She moves into the gap between the F- ring and the discovered in 2006, about 5,000 km wide Janus / Epimetheus dust ring, whose inner boundary Pandora 7,300 km away. It acts as an outer shepherd moon with its gravity on the F- ring of Saturn and causes the inner shepherd moon Prometheus deformations in the ring. Above all, Pandora has a stabilizing effect on the F ring; keeps them from outside and Prometheus inside the ring in its narrow shape, and prevents the union of the attractive forces of these two moons that the dust is distributed in width.

The orbit of Pandora appears chaotic; it is a consequence of four 121:118 - track resonances with Prometheus. The most noticeable changes in the orbit takes place approximately every 6.2 years, when the periapsis of Pandora with the apoapsis of Prometheus is on a line and the two bodies are separated a distance of about 1,400 km. Pandora itself disturbs the orbit of the inner neighbor Atlas to a certain degree, but far less than the inner shepherd moon Prometheus, with which Atlas is in a 54:53 - orbital resonance. This leads to deviations of the Atlas track with a length of up to 600 km (~ 0.25 ° ) of the precessing Keplerian orbit with a period of roughly three years. In addition, Pandora is in a 3:2 resonance with Mimas.

2008, further dynamics were discovered in this system, which indicates that small " moonlets " circulate within the F ring of Saturn. This moonlets, the S 4 (which may be the same body and have since not been sighted ) tentatively identified as S/2004 S 3 and S/2004 and S/2004 S 6 are referred to, are probably clumps of ring material and happen because of perturbations by the internal neighbors Prometheus continuously the narrow and densely core of the ring.

The moon orbits Saturn within a critical distance, the so-called Roche limit, which would bring a larger moon in this field to shatter. Probably Pandora is preserved only because of their small size or a loose internal structure of this fate.

Rotation

The rotation period is equal to the orbital period and Pandora has with how the Earth's moon, a synchronous rotation, which therefore also takes place within 15 hours, 5 minutes and 2.8 seconds. Your rotation axis is almost exactly perpendicular to its orbital plane.

Physical Properties

Size

Pandora has an average diameter of 80.6 km. Pandora appears to be a very irregularly shaped, extremely elongated object with dimensions of 103 × 80 × 64 km, wherein the longitudinal axis is aligned with Saturn on the images of the Cassini and Voyager spacecraft.

From the size Pandora is best compared with the Uranian moons Cressida and Juliet or the Neptune moon Thalassa.

The total area of ​​21,000 km ² Pandora is estimated, which corresponds approximately to the area of ​​Slovenia.

Internal construction

The mean density of Pandora is 0.49 g / cm ³ by far lower than that of the earth and even much lower than the density of Saturn; she is so low that Pandora would float on water. This indicates that the moon is composed mainly of water ice.

That Pandora Saturn within the Roche limit rotates, points out that it has either a very strong internal structure, or that it belongs to the so-called porous Rubble Piles, which, due to the relatively weak gravitational inside cavities. Due to the extremely low mean density, the latter hypothesis is more likely.

Surface

The surface of Pandora has many impact craters on more than Prometheus, Epimetheus and Janus but less than. It is possible to identify at least two larger impact crater 30 km in diameter. The surface also has beam systems.

Pandora has a relatively high albedo of about 0.60, which means that it has a very bright surface that reflects 60 % of the incident sunlight. On its surface is the acceleration of gravity 0.0034 m / s ², equivalent to about 3 ‰ of the earth. The average surface temperature of Pandora is estimated to be about -195 ° C ( 78 K).

Research

Pandora has an apparent magnitude of 16.3 m, which is 1:1900000 of the central planet. Since the discovery and confirmation of 1980 and the Voyager flybys Pandora has been studied by ground-based telescopes and the Hubble Space Telescope and its Bahnpararameter could be clarified.

Pandora has so far been visited by three spacecraft, notably by the flyby probes Voyager 1 on 12 November 1980 and Voyager 2 on August 1981 and the Saturn orbiter Cassini, orbiting Saturn since July 1, 2004 25. Pandora was repeatedly taken by Cassini targeted so that their size and shape, and their orbital parameters are now fairly well known. The next flybys of Cassini occurred during the 14th orbit around Saturn on 5 September 2005, when the spacecraft Pandora happened at a distance of 52,000 km. It was some well-resolved images are taken.

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