# Prometheus

Saturn XVI - 1980S27

Prometheus [pra-MEE-thee-us] is the third of Saturn's known satellites. It was discovered from photographs taken by Voyager during its encounter with Saturn by S. Collins and others. Prometheus acts as a shepherd satellite for the inner edge of Saturn's F Ring. The moon is extremely elongated about 145 by 85 by 62 kilometers (90 by 53 by 39 miles) in diameter. It has a number of ridges and valleys on its northern side. Several craters about 20 kilometers (12 miles) in diameter are visible, but it appears to be less cratered than its nearby neighbors Pandora, Janus and Epimetheus. The density of Prometheus has been estimated to be quite low, indicating that is a porous, icy body; however, there is a lot of uncertainty in these values.

## Prometheus Statistics

    Discovered by ........................... S. Collins & others
    Date of discovery ...................................... 1980

    Mass (kg) .......................................... 2.7e+17*
    Mass (Earth = 1) ................................. 4.5181e-08
    Radius (km) .................................. 72.5x42.5x32.5
    Radius (Earth = 1) ............................... 1.1367e-02
    Mean density (gm/cm^3) ................................. 0.7*

    Mean distance from Saturn (km) ...................... 139,350
    Rotational period (days) .................................. ?
    Orbital period (days) ................................ 0.6130
    Mean orbital velocity (km/sec) ........................ 16.54

    Orbital eccentricity .................................. 0.003
    Orbital inclination ..................................... 0.0°

    Escape velocity (km/sec) ............................. 0.0223

    Visual geometric albedo ................................. 0.6
    Magnitude (Vo) ......................................... 15.8

## Views of Prometheus

Prometheus (GIF, 16K)
This image of Prometheus was acquired by the Voyager 2 spacecraft on August 25, 1981. (Credit: Calvin J. Hamilton)

Shaded Relief Map of Prometheus (GIF, caption)
This image is a shaded relief map of Prometheus, the inner F Ring Shepherd satellite of Saturn. As with all maps, it is the cartographer's interpretation and not all features are necessarily certain given the limited data available. This interpretation stretches the data as far as is feasible. (Courtesy Phil Stooke)

Cylindrical Map of Prometheus (GIF, caption)
This image is a shaded relief map of Prometheus, the inner F Ring Shepherd satellite of Saturn. It is the same map as the above image, but reprojected to the Simple Cylindrical projection. As with all maps, it is the cartographer's interpretation and not all features are necessarily certain given the limited data available. This interpretation stretches the data as far as is feasible. (Courtesy Phil Stooke)

Prometheus and Pandora (GIF, 73K)
This image shows Prometheus and Pandora next to Saturn's F-ring. (Courtesy NASA/JPL)

## References

Stooke, P. J., "Shapes and Surface Features of Prometheus and Pandora," Earth, Moon and Planets, 62 (1993), 199-221.

Saturn Atlas Pandora

##### Author: Calvin J. Hamilton.