Pandora (moon)

Pandora

Pandora, as imaged by Cassini
Discovery
Discovered by	Collins, Voyager 1
Discovery date	October, 1980
Orbital characteristics [1]
Epoch December 31, 2003 (JD 2453005.5)
Semi-major axis	141720±10 km
Eccentricity	0.0042
Orbital period	0.628504213 d
Inclination	0.050°±0.004° to Saturn's equator
Satellite of	Saturn
Physical characteristics
Dimensions	104 × 81 × 64 km [2]
Mean radius	40.7±1.5 km [2]
Volume	≈ 280000 km^3
Mass	(1.371±0.019)×10^17 kg[2]
Mean density	0.49±0.06 g/cm^3[2]
Surface gravity	0.0026–0.0060 m/s^2 [2]
Escape velocity	≈ 0.019 km/s
Rotation period	synchronous
Axial tilt	zero
Albedo	0.6
Temperature	≈ 78 K

Pandora (/pænˈdɔərə/ pan-DOHR-ə; Greek: Πανδώρα) 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.^[3] In late 1985 it was officially named after Pandora from Greek mythology.^[4] It is also designated as Saturn XVII.^[5]

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.^[6][7] 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 moon's surface.^[8]

The orbit of Pandora appears to be chaotic, as a consequence of a series of four 118:121 mean-motion resonances with Prometheus.^[9] The most appreciable changes in their orbits occur approximately every 6.2 years,^[1] 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.^[1]

From its very low density and relatively high albedo, it seems likely that Pandora is a very porous icy body. There is a lot of uncertainty in these values, however, so this remains to be confirmed.

Gallery

• 

  Voyager 2 image of Pandora (August 1981).

• 

  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.

References

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Citations

1. Spitale Jacobson et al. 2006.
2. Thomas 2010.
3. IAUC 3532.
4. IAUC 4157.
5. USGS: Planet and Satellite Names and Discoverers.
6. Lakdawalla, E. (2014-07-05). "On the masses and motions of mini-moons: Pandora's not a "shepherd," but Prometheus still is". Planetary Society. Retrieved 2015-04-17.
7. Cuzzi, J. N.; Whizin, A. D.; Hogan, R. C.; Dobrovolskis, A. R.; Dones, L.; Showalter, M. R.; Colwell, J. E.; Scargle, J. D. (April 2014). "Saturn’s F Ring core: Calm in the midst of chaos". Icarus 232: 157–175. doi:10.1016/j.icarus.2013.12.027. ISSN 0019-1035.
8. Solar System, NASA: Pandora.
9. Renner et al. 2005.

Sources

• Marsden, Brian G. (October 31, 1980). "Satellites of Saturn" (discovery). IAU Circular 3532. Retrieved 2011-12-29.
• Marsden, Brian G. (January 3, 1986). "Satellites of Saturn and Pluto" (naming the moon). IAU Circular 4157. Retrieved 2011-12-29.
• Renner, Stéfan F.; Sicardy, Bruno; French, Richard G. (March 2005). "Prometheus and Pandora: Masses and orbital positions during the Cassini tour". Icarus 174 (1): 230–240. Bibcode:2005Icar..174..230R. doi:10.1016/j.icarus.2004.09.005.
• "Saturn: Moons: Pandora". Solar System Exploration: Planets. NASA. 4 Apr 2011. Retrieved 2011-12-29.
• Spitale, J. N.; Jacobson, R. A.; Porco, C. C.; Owen, W. M., Jr. (2006). "The orbits of Saturn's small satellites derived from combined historic and Cassini imaging observations" (PDF). The Astronomical Journal 132 (2): 692–710. Bibcode:2006AJ....132..692S. doi:10.1086/505206.
• Thomas, P. C. (July 2010). "Sizes, shapes, and derived properties of the saturnian satellites after the Cassini nominal mission" (PDF). Icarus 208 (1): 395–401. Bibcode:2010Icar..208..395T. doi:10.1016/j.icarus.2010.01.025.
• USGS/IAU (July 21, 2006). "Planet and Satellite Names and Discoverers". Gazetteer of Planetary Nomenclature. USGS Astrogeology. Retrieved 2011-12-29.

External links

• Pandora at NASA's Solar System Exploration
• Pandora at The Planetary Society