On May 18, the Cassini spacecraft entered the Saturn planetary system, where the gravitational pull of Saturn overtook the influence of the Sun and we crossed the outer limits of the most distant group of the planet's moons.
In this new image, the craft captured three moons. Prometheus (102 kilometers, or 63 miles across) and Pandora (84 kilometers, or 52 miles across), shepherd the planet's narrow F-ring. Prometheus overtakes Pandora in orbit around Saturn about every 25 days.
The F-ring is a narrow, ribbon-like structure, with a width seen in this geometry equivalent to a few kilometers. The two small, irregularly shaped moons exert a gravitational influence on particles that make up the F ring, confining it and possibly leading to the formation of clumps, strands and other structures observed there.
Slightly above the pair and to the right is another moon, Epimetheus (116 kilometers, or 72 miles across). The image was taken on May 1, 2004, at a distance of 31.4 million kilometers (19.5 million miles) from Saturn. The image has been magnified and greatly contrast-enhanced to aid visibility. It was released yesterday.
Early next month, the spaceship will make its closest approach to Phoebe, the largest member of the outer moon population and perhaps a captured asteroid. The probe will explore Saturn and its moons, including deploying its piggybacked Huygens probe, which will descend through the smog of the largest moon, Titan.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The imaging team is based at the Space Science Institute, Boulder, Colo.
