Pandora (moon)
A porous icy moon with chaotic orbit and disputed shepherd role.
Pandora is an inner satellite of Saturn, discovered in 1980 from photos taken by the Voyager 1 probe. It was provisionally designated S/1980 S 25 and officially named after Pandora from Greek mythology in late 1985. It is also designated as Saturn XVII. Pandora was thought to be an outer shepherd satellite of the F Ring, but recent studies indicate it does not play such a role; only Prometheus, the inner shepherd, contributes to the confinement of the narrow ring.
Quick Facts
- Pronounced
- p · æ · n · ˈ · d · ɔər · ə
- Adjective
- Pandoran
- Named After
- Πανδώρα Pandōra
- Mpc Name
- Saturn XVII
- Discoverer
- Stewart A. Collins / D. Carlson / Voyager 1
- Discovered
- October 1980
- Eccentricity
- 0.00419
- Satellite Of
- Saturn
Facts from the source article.
Lore & Background
Pandora was discovered in 1980 from photos taken by the Voyager 1 probe and was provisionally designated S/1980 S 25. In late 1985, it was officially named after Pandora from Greek mythology. It is also designated as Saturn XVII. The moon was initially thought to be an outer shepherd satellite of the F Ring, but recent studies indicate that it does not play such a role, and that only Prometheus, the inner shepherd, contributes to the confinement of the narrow ring. Pandora is more heavily cratered than nearby Prometheus and has at least two large craters 30 kilometres in diameter. The majority of craters on Pandora are shallow as a result of being filled with debris. Ridges and grooves are also present on the moon's surface. The orbit of Pandora appears to be chaotic as a consequence of a series of four 118:121 mean-motion resonances with Prometheus. The most appreciable changes in their orbits occur approximately every 6.2 years, when the periapsis of Pandora lines up with the apoapsis of Prometheus and the moons approach to within about 1,400 kilometres. Pandora also has a 3:2 mean-motion resonance with Mimas, and also a 21:19 mean-motion resonance with Epimetheus, but only while it is on the outer orbit relative to Janus. No such configuration with Janus exists. Due to their gravitational interactions with the rings, Prometheus and Pandora are expected to crash into each other or Mimas in the next 20 million years. From its very low density and relatively high albedo, it seems likely that Pandora is a very porous icy body. However, there is much uncertainty in these values, so this remains to be confirmed.
Reader's Guide
Pandora's significance lies in its role as a former candidate for a shepherd moon of Saturn's F Ring, a role now attributed solely to Prometheus based on recent studies. Its chaotic orbit, driven by a series of four 118:121 mean-motion resonances with Prometheus, leads to periodic close approaches every 6.2 years, when the moons come within about 1,400 kilometres of each other. This dynamical complexity, along with additional resonances with Mimas and Epimetheus, makes Pandora a key object for understanding orbital interactions among Saturn's inner moons. The moon's heavily cratered surface, with at least two large craters 30 kilometres in diameter and many shallow craters filled with debris, suggests a history of impacts and surface modification. Its very low density and relatively high albedo indicate it is likely a very porous icy body, though uncertainty remains. The predicted collision of Prometheus and Pandora with each other or with Mimas within the next 20 million years underscores the dynamic and temporary nature of these moons' orbits. Pandora's legacy is thus tied to its evolving scientific understanding, from shepherd to non-shepherd, and its role in the intricate gravitational dance of Saturn's inner satellite system.
More in Moons of Saturn 1-24
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