PSC

Home

News Center

Saturn’s Dynamic Ring

30 August 2008

Credit: NASA/JPL/Space Science Institute

NASA’s Jet Propulsion Laboratory (JPL) recently published a stunning image showing a small Saturnian moon, known as Prometheus, perturbing one of Saturn’s major rings, the dynamic F ring. The image was acquired by the Saturn-orbiter Cassini spacecraft.

Prometheus (86 km across) shines as a huge rock pulling at the nearby inner strand of the F ring. Gravitational effects of Prometheus are constantly reshaping this narrow ring. The brighter right side of the moon is lit by direct sunlight, and the glow around this side is due to light scattered within the camera optics. The fainter left side of Prometheus is lit by sunlight reflected off its parent giant planet.

Cassini was looking toward the sunlit side of the rings from about 40 degrees below the ringplane. The image was taken in visible light with Cassini’s narrow-angle camera, on 22 July 2008. The spacecraft was approximately 546,000 km from Saturn. Image scale is 3 km per pixel.

Saturn’s rings are composed of icy particles ranging in size from microns up to several meters. The F ring was discovered in 1979 by the Pioneer 11 spacecraft. It is approximately 280,000 km in diameter, and is only a few hundred kilometers wide.

A spectacular image showing Prometheus (right) and Pandora (left), the shepherd moons of Saturn’s active F ring
Credit: NASA/JPL/Space Science Institute

Interestingly, the F ring is associated with two “shepherd” moons, Prometheus and Pandora (approximately 84 km across). The two moons orbit Saturn very close to the F ring; Prometheus is the innermost of the two satellites. The gravitational influence of these small moons on the ring-particles determines the shape of the F ring. Prometheus is responsible for kinks, and other interesting structures in the F ring. The F ring is perhaps the most active planetary ring in the Solar System, showing rapidly changing features.

BASEF 2023 Program