ESA Science & Technology04-Jul-2005 14:21:33

Saturn's Moons


XVI - Discovered by Collins & Carlson (1980)

Physical Parameters

Orbital Parameters

Radius (km)


Radius (km)

139 353

Mean Density (kgm-3)



14d 42h 43m

Mass (kg)

3.3 x 1017

Velocity (kms-1)


Magnitude (V0)


Rotational Period


Escape Velocty (kms-1)




Mean Surface Albedo


Inclination ( )


Knowledge before Cassini-Huygens

Pandora and Prometheus together act as shepherd moons for Saturn's thin, knotted F ring, with Pandora maintaining the outer edge and Prometheus maintaining the inner edge of the ring.

Prometheus has an elongated shape with radii of about 74 by 50 by 34 kilometres. The surface is covered with a number of ridges and valleys on the northern side of the satellite, along with several craters roughly 20 kilometres in diameter.

*Note: in the following section all images courtesy NASA/JPL/Space Science Institute unless stated otherwise.

30 September 2004

Cassini Instrument: Imaging Science Subsystem

Date: 01 July 2004

Distance: 181 000 - 190 000 km from Saturn

Scale: ~11 km per pixel

Images Notes: Wide angle mode, magnified x5, a composite of nine raw images combined to improve resolution and reduce noise

The component images were taken over about ten and a half minutes. During that time, the spacecraft's motion caused some blurring of the F ring in the background. Cassini was below the ring plane at the time the images were obtained, and the view here is across the rings toward the distant arm of the F ring. Sunlight is coming from below left.

03 December 2004

Cassini Instrument: Imaging Science Subsystem

Date: 29 October 2004

Distance: 782 000 km

Scale: 4.7 km per pixel

Phase Angle: 147

Image Details: Narrow Angle mode, visible wavelength, magnified x2, contrasted enhanced

The F ring resolves into five separate strands in this close-up view. Potato-shaped Prometheus is seen here, connected to the ringlets by a faint strand of material. Imaging scientists are not sure exactly how Prometheus is interacting with the F ring here, but they have speculated that the moon might be gravitationally pulling material away from the ring. The ringlets are disturbed in several other places. In some, discontinuities or kinks in the ringlets are seen; in others, gaps in the diffuse inner strands are seen. All these features appear to be due to the influence of Prometheus.

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