Added 1 new A* page:Saturn's moon Hyperion (the Titan of "watchfulness and observation" in Greek mythology) was the first known non-round moon when it was discovered in 1848--which was some feat, considering that this irregularly shaped, dark, and highly pockmarked moon only averages about 270 km in diameter (it's about 360 km from tip to tip along its longest axis). It kinda looks like a potato in photos taken by the Cassini probe (this one's from 2005):
image by NASA (source)
It is the largest irregular moon of which we have good pictures--Neptune's faceted Proteus is larger, but hasn't been seen clearly yet. Hyperion has a very low density: calculations based on its size, orbit, and so forth estimate it to be composed mostly of water ice rather than rock--the dark color is thought to come from a thin coating of dust--and to be as much as 46% empty space, what with all those honeycombs of craters and so on, which have caused the moon to be likened in appearance to a giant sponge.
This strange potato sponge moon is also the only moon in our solar system known to rotate chaotically: likely because of its irregular shape, eccentric orbit, and proximity to Saturn's largest moon, Titan, Hyperion's axis of rotation wobbles so much that its orientation at any particular time is hard to predict.
Unique as it is, Hyperion is just one of 61 confirmed moons of Saturn! About half of them are distant, tiny things under 10 km across, but still!
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