Shepherd moons are the outer space answers to some of earth’s quirkiness! More along that line, they are caretakers of the planet’s rings. At least that is the theory surrounding the smaller moon like substances that appear to put fences around the rings of the moon, not allowing them to scatter far afield. Saturn, in particular show these gravitational fields.
On Saturn, the planet with sensational moons that have caused astronomers to say this is the most dazzling of planets is nicknamed by them, the jewel planet. One f-ring stands out particularly as one worth guarding. These ring herders are likewise named appropriately, Prometheus and Pandora. Supposedly, observers have noted that these literary shepherds not only guard the ring, but are likewise responsible for its “braids and kinks.” An image can be seen at NASA’s Jet Propulsion Laboratory. Caducean, possibly?
(Prometheus is the Greek god of fire, and Pandora is the Greek goddess thought to have opened the box with all of mankind’s evils and turned them loose upon the world. At least that was the Ancient Greeks explanation for the seven deadly sins, lust, greed, gluttony, envy, anger, pride, sloth. )
The Cassini Equinox Mission, that completed its four years of surveying and recording Saturn was completed in 2008, is responsible for the information about the Shepherd moons. The equinox mission was an extension of that mission that was completed in September 2010. Now another extension has been assigned and it is differentiated by the labeling, Cassini Solstice Mission.
Interesting enough, the two moons Prometheus and Pandora, speculative as they are, work as shepherds by using the force of gravity to control the drift of the ring of debris that make up these rings. Each to its opposing force: Pandora prevents the ring from moving outward into the atmosphere, and Prometheus prevents it from moving inward toward Saturn.
How, in earthy language, should these be viewed? The shepherding rings as fences around glitzy mansion whose mission is to prevent theft and the carrying off of the precious jewels of the illustrious ring of Saturn. Or as tree lights decorating a surrounding fence might be another option.
In though, however, the naming is quite appropriate. Much of the heavenly bodies are named for mythological creatures and in this instance, the two shepherds guarding the F-ring is quite appropriately carrying out their mission by retribution. Both of these mythological creatures were naughty.
Prometheus stole fire and Pandora was guilty of introducing the world to torment. Thus Pandora’s duty is to contain these disturbances of the universe and not let further harm come to mankind; Prometheus’ job is to keep the planet from being torched by the brilliant energy of the f-ring.
Cassini launched in 1997, was launched to study Titan, Saturn’s largest and most well known moon. It arrived there Jan. 14, 2005, and has since been reporting back much information. This was the source of the shepherd moon observations. In time and with other missions that survey other planets, it may well be that most of the planet’s have shepherding moons surrounding and protecting their rings, if the truth be known.
Source:
http://saturn.jpl.nasa.gov/faq/FAQSaturn/
http://saturn.jpl.nasa.gov/photos/imagedetails/index.cfm?imageId=817
