Prometheus (moon)
Moon of Saturn
From Wikipedia, the free encyclopedia
Prometheus /prəˈmiːθiːəs/ is an inner satellite of Saturn. It was discovered on 24 October 1980 from images taken by the Voyager 1 probe, and was provisionally designated S/1980 S 27.[6] In late 1985 it was officially named after Prometheus, a Titan in Greek mythology.[7] It is also designated Saturn XVI.[8]
D. Carlson
Voyager 1
Prometheus image from Cassini (December 26, 2009) | |
| Discovery | |
|---|---|
| Discovered by | Stewart A. Collins D. Carlson Voyager 1 |
| Discovery date | 24 October 1980 |
| Designations | |
Designation | Saturn XVI |
| Pronunciation | /prəˈmiːθiːəs/[1] |
Named after | Προμηθεύς Promētheys |
| Adjectives | Promethean, -ian /prəˈmiːθiːən/[2] |
| Orbital characteristics[3]: 4 | |
| 139378 km | |
| Eccentricity | 0.00223 |
| 0.612990 d | |
| Inclination | 0.008° |
| Satellite of | Saturn |
| Physical characteristics | |
| Dimensions | 137.0 × 81.0 × 56.2 km (± 1.0 × 2.8 × 0.8 km)[4]: 2 |
| 85.6±1.4 km[4]: 2 | |
| Volume | 327740±1710 km3[5]: 4 |
| Mass | (1.59720±0.00072)×1017 kg[a] |
Mean density | 0.4873±0.0026 g/cm3[5]: 4 |
| 0.0007–0.0056 m/s2[4]: 3 | |
| 0.018 km/s at longest axis to 0.028 km/s at poles | |
| synchronous[4]: 4 | |
| assumed zero | |
| Albedo | 0.67±0.07[3]: 7 |
| Temperature | ≈ 74 K |
Prometheus is extremely elongated, measuring approximately 137 km × 81 km × 56 km (85 mi × 50 mi × 35 mi). The surface is heavily cratered, giving it a similar appearance to nearby Epimetheus and Janus.[9] It has several ridges and valleys and a number of impact craters of about 20 km (12 mi) diameter are visible. From its very low density and relatively high albedo, it is likely that Prometheus is a very porous icy body.
Interactions with F Ring and other moons
Prometheus is a shepherd satellite for the inner edge of Saturn's narrow F Ring. Pandora orbits just outside the F Ring, and has traditionally been viewed as an outer shepherd of the ring; however, recent studies indicate that only Prometheus contributes to the confinement of the ring.[10][11]
Images from the Cassini probe show that Prometheus's gravitational influence creates kinks and knots in the F Ring as it shepherds material from it. The orbit of Prometheus appears to be chaotic, due to a series of four 121:118 mean-motion resonances with Pandora.[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, as they approach to within approximately 1400 km. Prometheus is itself a significant perturber of Atlas, with which it is in a 53:54 mean-longitude resonance.[13]
Prometheus also participates in a 17:15 mean-motion resonance with Epimetheus, but only while it is on the outer orbit relative to Janus. No such configuration with Janus exists.[14]
Physical characteristics
The surface of Prometheus can be distinguished into two types of terrain, both equally cratered[4] and separated from each other by long scarps, one of which could be indicative of an exposed core section. This core section would make up roughly two-thirds of the total volume of Prometheus.[9]
Prometheus' elongated shape could be a result of the low-speed merging of several similar-sized bodies.[4]
Gallery
Selected images
Prometheus pulling material from the F Ring
Prometheus tugging kinks into the F Ring
Voyager 2 (August 25, 1981) image
Cassini image (with moon's Saturn-facing end at lower right) reveals a surface covered with a blanket of fine material.
Image from Jan. 27, 2010. Saturnshine illuminates the moon's night side.
Brightened version of same image
Prometheus flyby
(December 6, 2015)
Animations
- Prometheus collides with the F ring, pulls a streamer, and leaves behind a dark channel. 12 seconds 107 kbit/s
- Movie of Prometheus and the F Ring looped once. 5 seconds 48 kbit/s
