In 1610 Galileo pointed his crude spyglass at Saturn and was dumbfounded by what he saw: “The planet Saturn is not alone, but is composed of three, which almost touch one another and never move nor change with respect to one another.” Worse, the two bulging planets on each side of the main planet had disappeared when he looked again a few months later. “What is to be said concerning such a strange metamorphosis?” he cried. Eventually, the frustrated Galileo decided never to look at Saturn again.
Now, of course, we have much better telescopes, and we know that Galileo was looking at the planet’s unique set of wide, thin rings. Seen broadside, they resembled companion planets through Galileo’s weak lenses; later, seen edge on, they shrank to nothingness—an invisible sliver. But nearly 400 years after Galileo’s observations, Saturn still teases astronomers, and the closer we look, the more oddities we see. Saturn’s magnificent rings, for example, consist of trillions of bits of ice, some no bigger than a speck of dust, making up a weird and complex system of satellites. The ring particles are so puny that you would expect them to quickly scatter and fall into the planet, yet they are still there. And the planet is so loosely built that it would float on water.
At another extreme, Saturn’s giant moon Titan seems more like a planet in its own right, larger than Mercury and cloaked in a dense atmosphere. Titan’s surface seems to be covered with ethane oceans and an organic goo that may resemble the Earth’s early surface chemistry, but nobody knows for sure, because astronomers can’t see through the moon’s maddeningly opaque orange fog. In between, Saturn has at least 30 other smaller moons, some smooth, some battered, some strangely mottled.
