Pandora, Saturn’s irregularly-shaped, icy moon
Credit: NASA/JPL/Space Science Institute

NASA recently published an amazing image of Pandora, an icy potato-like Saturnian moon. The image was acquired by the Saturn-orbiting Cassini spacecraft, during its flyby of Pandora, on 3 June 2010. Cassini obtained the image at a distance of approximately 101,000 km from Pandora.

Interestingly, the smaller moons of the Solar System are irregular in shape, as their gravitational fields are too weak to make them round. The planets, for instance, are spherical or oblate, due to their much larger masses and stronger gravitational fields. 

Pandora (81 km across) orbits beyond a thin ring of Saturn, termed the F ring. Saturn’s magnificent rings are referred to by letters of the English alphabet, in order of discovery. The F ring was discovered in 1979 by the Pioneer 11 spacecraft. It is one of the most interesting and dynamic features of Saturn’s extensive ring system. The F ring is about 280,000 km in diameter, but it is very narrow, being just a few hundred kilometers wide.

Intriguingly, the motions of the particles constituting the F ring are controlled by two “shepherd moons”, Pandora and its close companion Prometheus (86 km across). Pandora’s orbit lies outside the F ring, while Prometheus circles within the F ring. The gravitational influence of Prometheus changes the structure of the F ring dramatically, giving rise to weird formations of particles, such as kinks and clumps, within the F ring.

Pandora orbits Saturn every 15 hours, approximately, at a distance of nearly 142,000 km.   

Further Reading

Cassini Mission Homepage
http://saturn.jpl.nasa.gov/index.cfm

Aymen Mohamed Ibrahem
Senior Astronomy Specialist