Pandora is one of the inner moons of Saturn and the outer shepherd moon for the F-ring. It was discovered in 1980 from Voyager 1 photos and is also known as Saturn XVII.

 

Pandora is heavily cratered and, as revealed by the Cassini probe during its passage of the moon at a distance of 52,000 kilometers on 5 September 2005, there are small grooves and ridges in the dust-fine icy material that has collected over the craters. The two largest craters identified measure about 30 kilometers (19 miles) across.

 

Pandora and Prometheus, the inner shepherd of the F-ring, both follow chaotic orbits as a result of their gravitational interaction. Each time Pandora passes inside Prometheus, which happens about every 28 days, the two moons give each other a gravitational kick. Because neither moon's orbit is quite circular, the distance between them on those occasions – hence the strength of the kick - varies. The perturbations lead to changes in motion that are not periodic or predictable. This is the first observation ever of chaotic orbital motions in the Solar System. A larger moon of Saturn, Hyperion, had earlier been found to have chaotic rotation around its axis.

 

discovery	1980, by S. Collins from Voyager 1 data
semimajor axis	141,720 km (88,080 mi)
diameter	103 × 80 × 64 km (64 × 50 × 40 mi)
mean density	0.5 g/cm3
escape velocity	0.019 km/s (68 km/h, 43 mph)
orbital period	0.629 days (15 h 6 min.)
orbital eccentricity	0.004
orbital inclination	0.05°
visual albedo	0.6