Pandora (moon)
| View of Pandora's western hemisphere. a
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]: 7 | |
| Semi-major axis | 141712 km |
| Eccentricity | 0.00419 |
| Orbital period (sidereal) | 0.628503 d |
| Inclination | 0.050° |
| Satellite of | Saturn |
| 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[5] |
| 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[3]: 4 |
| Axial tilt | assumed zero |
| Albedo | 0.62±0.08[2]: 7 |
| Temperature | ≈ 78 K |
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.[6] In late 1985, it was officially named after Pandora from Greek mythology.[7] It is also designated as Saturn XVII.[8]
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.[9][10] 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.[11]
The orbit of Pandora appears to be chaotic as a consequence of a series of four 118:121 mean-motion resonances with Prometheus.[12] The most appreciable changes in their orbits occur approximately every 6.2 years,[13] 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,[13] 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.[14]
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.[15][16]
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.
References
- Back to citation Robert Kolvoord (1990) Saturn's F ring: imaging and simulation, p. 104
- Back to citation occurrence 2.0 Back to citation occurrence 2.1 Ciarniello et al. 2024.
- Back to citation occurrence 3.0 Back to citation occurrence 3.1 Back to citation occurrence 3.2 Back to citation occurrence 3.3 Thomas & Helfenstein 2020.
- Back to citation occurrence 4.0 Back to citation occurrence 4.1 Lainey et al. 2023.
- Back to citation Calculated from the standard gravitational parameter GM = (9.058±0.011)×10−3 km3·s–2 given by Lainey et al. (2023), divided by the gravitational constant G = 6.6743×10−2 km3·kg–1·s–2. Lainey et al. 2023.
- Back to citation IAUC 3532.
- Back to citation IAUC 4157.
- Back to citation USGS: Planet and Satellite Names and Discoverers.
- Back to citation 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.
- Back to citation 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. Bibcode:2014Icar.232.157C. doi:10.1016/j.icarus.2013.12.027. ISSN 0019-1035.
- Back to citation Solar System, NASA: Pandora.
- Back to citation Renner et al. 2005.
- Back to citation occurrence 13.0 Back to citation occurrence 13.1 Spitale Jacobson et al. 2006.
- Back to citation Cooper, N. J; Renner, S; Murray, C. D; Evans, M. W. (2014-12-24). "SATURNʼS INNER SATELLITES: ORBITS, MASSES, AND THE CHAOTIC MOTION OF ATLAS FROM NEW CASSINI IMAGING OBSERVATIONS". The Astronomical Journal. 149 (1): 27. arXiv:1406.6492. doi:10.1088/0004-6256/149/1/27. ISSN 1538-3881.
- Back to citation Poulet and Sicardy 2001.
- Back to citation Esposito and De Stefano 2018.
Bibliography
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. Archived from the original on 2 June 2015. 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". 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.
- Thomas, P. C; Helfenstein, P. (July 2020). "The small inner satellites of Saturn: Shapes, structures and some implications". Icarus. 344: 20. Bibcode:2020Icar.34413355T. doi:10.1016/j.icarus.2019.06.016. S2CID 197474587. 113355.
- Lainey, V; Rambaux, N; Cooper, N; Dahoumane, R; Zhang, Q. (February 2023). "Characterising the interior of five inner Saturnian moons using Cassini ISS data". Astronomy & Astrophysics. 670: 6. Bibcode:2023A&A...670L.25L. doi:10.1051/0004-6361/202244757. L25.
- Ciarniello, Mauro; Filacchione, Gianrico; Nicholson, Philip D; Hedman, Matthew M; Charnoz, Sebastien; Cuzzi, Jeffrey N; El Moutamid, Maryame; Hendrix, Amanda R; Rambaux, Nicolas; Miller, Kelly E; Mousis, Olivier; Baillié, Kevin; Estrada, Paul R; Waite, J. Hunter (2024-09-17). "The Origin and Composition of Saturn's Ring Moons". Space Science Reviews. 220 (7): 72. doi:10.1007/s11214-024-01103-z. ISSN 1572-9672.
- Esposito, L. W; De Stefano, M. (2018). "Space Age Studies of Planetary Rings". In Murray, Carl D; Tiscareno, Matthew S. (eds.). Planetary Ring Systems: Properties, Structure, and Evolution. Cambridge Planetary Science. Cambridge: Cambridge University Press. pp. 3–29. doi:10.1017/9781316286791. ISBN 978-1-107-11382-4.
- Poulet, F; Sicardy, B. (2001-04-01). "Dynamical evolution of the Prometheus--Pandora system". Monthly Notices of the Royal Astronomical Society. 322 (2): 343–355. Bibcode:2001MNRAS.322.343P. doi:10.1046/j.1365-8711.2001.04128.x. ISSN 0035-8711.