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Lists (8)

Prometheus, Pandora, Janus, Epimetheus, and Mimas; these are the moons that shepherd Saturn’s rings.

The rings are only 400 million years old, the result of a passing Kuiper belt ice asteroid being stripped to its core when it passed Saturn too closely.

Mimas, the bull’s-eye moon, is 400 kilometers in diameter, while its crater Herschel is 140. The Herschel impact nearly blew Mimas apart.

Hyperion is a fragment of a similar collision that did blow a moon apart; it is shaped like a hockey puck. The impact caused flash steam explosions across a plane and split the moon as if spalling granite. The facet left behind is pocked like a wasps’ nest by a field of rimless dust-filled craters.

Pandora is shaped like a jelly bean.

Tethys and Dione were both about 1,100 kilometers across (think France), both fractured all over their surfaces, etched by canyons with mile-high walls. Tethys’s Ithaca Chasma is twice as deep and four times as long as the Grand Canyon, and a thousand times older, very battered by Saturn’s everlasting civil wars.

Dione, on the other hand, was disassembled by self-replicating ice cutters in the 2110s, and the Hector-sized segments were then directed downsystem to Venus. They struck Venus on a line parallel to the equator and provided Venus with a deep ocean bed and the water to fill it, while also knocking a good bit of the choking Venusian atmosphere off into space.

Rhea is as wide as Alaska, with the usual plethora of craters, including fresh ones that throw bright ice rays out from their centers.

Iapetus orbits seventeen degrees out of the plane of Saturn’s equator and thus has one of the best views of the rings; is therefore popular. The bulge is the biggest city in the Saturnian system.

Epimetheus is a misshapen pile of loosely consolidated rubble. It switches orbits with the moon Janus every eight years; they are co-orbital moons, very rare—a sign of past impacts.

Enceladus is covered by braided spills of ice. No craters—the ice surface is too new, as it is continuously resurfaced from the liquid-water ocean in the depths. Heat sources boil some of this carbonized water, creating geysers that shoot many kilometers into space. The water quickly freezes in its flight, and some of it makes it up to the slender E ring; the rest falls back down and under its own weight turns to firn and then back to ice again. A suite of microscopic life-forms was discovered in the Enceladan ocean in the year 2244, and scientific stations have been established on its surface, as well as a cult of votaries who ingest a suite of the alien life-forms, to unknown effect.

There are twenty-six irregular small moons. These are all Kuiper belt objects, captured as they crossed Saturn’s earliest gas envelope. Phoebe, at 220 kilometers across, is the largest of these, and it has a retrograde and highly inclined orbit, twenty-six degrees out of the plane; thus another popular viewing platform.

Titan, by far the largest Saturnian moon, is bigger than Mercury or Pluto. More about Titan later.