Prometheus image from Cassini (December 26, 2009)
|Discovered by||Collins, Voyager 1|
|Discovery date||October, 1980|
|Orbital characteristics |
|Epoch 31 December 2003 (JD 2453005.5)|
|Semi-major axis||139,380 ± 10 km|
|Orbital period||0.612990038 d|
|Inclination||0.008 ± 0.004° to Saturn's equator|
|Dimensions||135.6×79.4×59.4 km |
|Mean radius||43.1 ± 2.7 km |
|Volume||~340,000 km³ |
|Mass||1.595 ± 0.015 ×1017 kg |
|Mean density||0.48 ± 0.09 g/cm³ |
|Equatorial surface gravity||0.0013–0.0058 m/s² |
|Escape velocity||~0.019 km/s|
In late 1985 it was officially named after Prometheus, a Titan in Greek mythology. It is also designated Saturn XVI (16). Pronunciation for Prometheus is //, US dict: prō·mē′·thē·əs; Greek: Προμηθεύς.
This small moon is extremely elongated, measuring about 136 by 79 by 59 km. It has several ridges and valleys and a number of impact craters of about 20 km diameter are visible, but it is less cratered than nearby Pandora, Epimetheus and Janus. From its very low density and relatively high albedo, it seems likely that Prometheus is a very porous icy body. There is a lot of uncertainty in these values, however, and so this remains to be confirmed.
Interactions with F Ring and other moons
Prometheus acts as a shepherd satellite for the inner edge of Saturn's F Ring. Recent images from the Cassini probe show that the Promethean gravitational field creates kinks and knots in the F Ring as the moon 'steals' material from it. The orbit of Prometheus appears to be chaotic, as a consequence of a series of four 121:118 mean motion resonances with Pandora. 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 1400 km. Prometheus is itself a significant perturber of Atlas, with which it is in a 53:54 mean longitude resonance.
- 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.
- 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". 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.
Media related to Prometheus (moon) at Wikimedia Commons
- "Cassini–Huygens: Multimedia-Videos / Soft Collision". NASA. Archived from the original on 29 October 2007. "Prometheus slowly collides with the diffuse inner edge of Saturn's F ring ... pulls a streamer of material from the ring and leaves behind a dark channel."
- Prometheus Profile at NASA's Solar System Exploration site
- The Planetary Society: Prometheus
- 3-D anaglyph view of Prometheus