Pandora (moon)

This article is about the moon of Saturn. For the fictional moon in the Avatar franchise, see Fictional universe of Avatar. For the asteroid, see 55 Pandora.

Pandora is an inner satellite of Saturn. It was discovered in 1980 from photos taken by the Voyager 1 probe and was provisionally designated S/1980 S 26.^[5] In late 1985, it was officially named after Pandora from Greek mythology.^[6] It is also designated as Saturn XVII.^[7]

Pandora

View of Pandora's western hemisphere.[a]
Discovery
Discovered by	Stewart A. Collins D. Carlson Voyager 1
Discovery date	October 1980
Designations
Designation	Saturn XVII
Pronunciation	/pænˈdɔːrə/
Named after	Πανδώρα Pandōra
Adjectives	Pandoran[1]
Orbital characteristics [2]
Epoch December 31, 2003 (JD 2453005.5)
Semi-major axis	141720±10 km
Eccentricity	0.0042
Orbital period (sidereal)	0.628504213 d
Inclination	0.050°±0.004° to Saturn's equator
Satellite of	Saturn
Group	Possible outer shepherd moon of the F Ring
Physical characteristics
Dimensions	103.0 × 79.0 × 63.0 km (± 0.6 × 0.6 × 0.4 km)[3]: 2
Mean diameter	80.0±0.6 km[3]: 2
Volume	268990±860 km3[4]: 4
Mass	(1.357±0.002)×1017 kg[b]
Mean density	0.5045±0.0017 g/cm3[4]: 4
Surface gravity	0.0022–0.0061 m/s2[3]: 3
Escape velocity	0.019 km/s at longest axis to 0.024 km/s at poles
Synodic rotation period	synchronous
Axial tilt	zero
Albedo	0.6
Temperature	≈ 78 K

Pandora was thought to be an outer shepherd satellite of the F Ring. However, 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.^[8][9] It is more heavily cratered than nearby Prometheus and has at least two large craters 30 kilometres (19 mi) 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.^[10]

The orbit of Pandora appears to be chaotic as a consequence of a series of four 118:121 mean-motion resonances with Prometheus.^[11] The most appreciable changes in their orbits occur approximately every 6.2 years,^[2] when the periapsis of Pandora lines up with the apoapsis of Prometheus and the moons approach to within about 1,400 kilometres (870 mi). Pandora also has a 3:2 mean-motion resonance with Mimas.^[2]

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.

Gallery

• 
  Voyager 2 image of Pandora (August 1981).
• 
  View of the moon, taken during September 2005 flyby by Cassini.
• 
  Pandora as seen from the Cassini probe in 2005; the rings of Saturn are in the background.
• 
  Cassini captured this close view of Saturn's moon Pandora during the spacecraft's flyby on June 3, 2010.