Cassini Encounters Prometheus
17 April 2007


Credit: NASA/JPL/Space Science Institute


NASA recently published a spectacular image of Saturn's small moon Prometheus (102 km across), acquired by the Saturn-bound Cassini spacecraft, which was looking on the unlit side of the planet's magnificent rings.


The image shows the irregularly-shaped moon gliding between Saturn's bright A ring and kinky F rings. The kinks in narrow F ring are due to the Prometheus's gravitational influence.


The F ring was discovered in 1979. It is only a few hundred km wide. Prometheus and Pandora (84 km across) are the shepherd moons of the F ring.



Potato-shaped moons, Prometheus and Pandora, shepherding Saturn's F ring

Credit: NASA/JPL/Space Science Institute


Prometheus is the inner shepherd moon of the F ring. It has a rugged terrain. It orbits Saturn every 0.61 days, at a distance of approximately 140,000 km. Pandora orbits Saturn every 0.63 days, at a distance of approximately 142,000 km.


Intriguingly, Prometheus perturbs the structure of the F ring, creating kinks, knots and gores in the ring.



A Cassini close-up image of Pandora

Credit: NASA/JPL/Space Science Institute


The image was taken in visible light with the Cassini's narrow-angle camera on 24 February 2007, at a distance of approximately 1.5 million km from Prometheus. Image scale is 9 km per pixel.


Further reading

Three Tiny Moons Align

The Shadows of Saturn's Rings

Cassini-Huygens Mission to Saturn

Aymen Mohamed Ibrahem

Senior Astronomy Specialist


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