Saturn’s outermost bright ring, the A-ring, and its sixth-largest moon, Enceladus, enjoy a symbiotic-like relationship recently discovered by the space probe Cassini. Separated by only 62,000 miles (100,000 km), Eceladus is six times closer than the Moon is to the Earth. The relationship as observed by the spacecraft Cassini involves Enceladus delivering a portion of its mass directly into the outer edge of the A-ring. The mass is expelled by ice geysers on Enceladus, which in 2006 were found to be responsible for the content of the E-ring. The E-ring is the outermost ring, bright or dull, and extremely wide. These ice geysers, rather than expelling molten rock, erupt volatiles such as water, ice, methane or ammonia. Tidal friction creates heat in the inner part of Enceladus. As the particles and gas are ejaculated from the interior of Enceladus, they become electrically charged by sunlight and interact with other atoms and electrons. This “plasma” is subjected to magnetic influence and become swept into orbit around Saturn. If they are carried into the A-ring by the powerful attraction of Saturn, they become lodged permanently. The A-ring then is basically a sponge, sucking up all this debris from Enceladus.

  Plumes from Enceladus that migrate into Saturn’s A-ring

Enceladus was discovered in 1789 by William Herschel. The Voyager spacecraft passed by it in the 1980’s and determined it to be 300 miles (500 km) wide. At this size, it could fit inside the state of Arizona or inside the British Isles. It seems to reflect 100% of the sunlight hitting it. Voyager 1 found that it actually orbits in the densest part of the E-ring, which makes me wonder which came first; Enceladus or the ring.

The backlit E ring, with Enceladus silhouetted against it at center.  The moon's south polar jets erupt brightly below it, while tendrils of the E Ring wrap around it.The E-ring with Enceladus at center.

I find the rings of Saturn amazing, and the action of both Saturn and Jupiter as well. Hopefully we’ll discover more about the material in the rings as time goes by.