Rhea
- This icy moon of Saturn is less than half the size of our own moon.
- It is only 1,530 km (950 miles) in diameter.
- Its orbit is smack in the middle of Saturn's satellite system.
- Just inside big brother Titan's orbit.
- Spectroscopic observations have determined that it has no atmosphere.
- Rhea's surface is a bright material which reflects 60 percent of the sunlight which reaches it.
- Rhea's surface is mostly composed of frozen water and a small amount of darker soil.
- The surface appears to be "sandblasted" by meteorites.
- Rhea has an appearance of creamy white, finely crushed ice.
- A wilderness of craters was revealed by Voyager 1 photos.
- Continuous random bombardment seems to have occurred since the formation of the planets.
- Rhea shows little or no signs of volcanism, tidal heating, or geologic activity.
- Scattered narrow, sinuous fissures and ragged rays of bright material do appear on the surface.
- Rhea has a low density - only 1.3 grams/cm3.
- Compare that to an average density of 1.0 grams/cm3 for rock.
- These numbers imply that Rhea is a giant snowball!
- Saturn's moons are noted for their low densities.
- As far as moons go, they have the lowest of any.
- In this zone of the solar system, world-building material comprised mainly of ice, not rock.
- "Rhea gives us a good opportunity to learn about the evolution of a fairly large world whose geology is controlled by frozen water instead of familiar lavas and soils."
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