Saturn - The Misnamed
Over the last few months we have recounted the planets, less as astronomical objects but more as their mythic Roman deities. Often there was a reasonable similarity. Mercury is the most fleet-footed god and is the swiftest planet. Venus is the fairest goddess with Moon-like phases the ancients equated with women. Ruddy Mars is the savage god of war. Mighty Jupiter is first among the pantheon and is the greatest of the planets.This duality fails with Saturn. His mythical and the scientific natures diverge. The word saturnine means of course, sad, gloomy and dour. In mythology, Saturn was of the race of titans, the fore bearers of the gods. Indeed Saturn was Jupiter's father. No god or titan was ever more grim or foreboding. Saturn knew that one of his children would overthrow him. To avoid this fate he swallowed his children at birth. Jupiter's mother having seen the fate of her eleven older children determined to save Jupiter. She fed Saturn a boulder, thus allowing Jupiter to be raised by nymphs until he could challenge his father.Yet Saturn the planet is a soft pastel blend of off white and palest yellow, hardly a grim dour hue. Saturn is bedecked with the gaudy Rings which make it instantly identifiable to almost everyone. Swarming about this planet are seven moons bright enough to be seen with modest telescopes. Saturn it is a beguiling world loved by everyone who sees it for the first time.More than half a century ago while visiting an amateur astronomer I had my first look through a "real" telescope. The very first object I ever saw in this telescope was Saturn. To a seven year old boy, it was literally magical. Floating against a dark field was a small but crystal clear ball with Rings. No grim forbidding world could have captivated a small boy but this pearl like world with its Ring was enthralling.Saturn is not the heavy dark world in at least another way. Given its volume and its mass, Saturn is the least dense world in the solar system. In fact if there was an ocean large enough to hold Saturn it would float. All the other planets and asteroids would sink like stones. [Not very surprising since most of them are in fact largely stones].Saturn's largest moon Titan is unique among the satellites in having a substantial atmosphere. Another of its moons Iapetus is variable in brightness. When NASA flew a spacecraft through the system, we were able to see that one side is nearly coal black and the other is much lighter. Scientists speculate that this two toned world was once all one shade but collided with a body of another color.We have long known that Saturn's Ring could not be solid. A single solid Ring would spin too slowly to maintain orbital velocity near the planet while spinning too rapidly at the outermost edge. The differential velocities would tear the Ring into shreds which in turn would crumble into little pieces. The Ring is very thin. If the Ring were reduced in size so that it would fit in a football stadium, it would be thinner than a sheet of paper.There are two gaps in the Rings which can be spotted with moderate telescopes. The larger, called Cassini's Division, is an area where the joint gravity of Saturn's inner Moons sweeps the area free of particles. The very thin Encke Division, near the outer edge of the Rings is caused by another process. A small moon, Pan, pushes its way through the ring, acting as a snowplow.All and all, Saturn was poorly named. I've often thought that a better name would have been Bacchus. Here was a merry god indeed loved by all who met him. He wore an ivy wreath (his Ring no doubt) and was attended by a bevy of reveling beauties (and what else can his Moons be?). He was often slightly tilted to one side or the other, true of both the tipsy god and the planet most obviously canted one way or the other.