My Favorite Moon (Science Advent 9)

(Every day until Christmas, I’ll be posting a science-related image.)

Day 9

Saturn's strange moon Hyperion, one of the largest irregularly-shaped objects in the Solar System.
Saturn’s strange moon Hyperion, one of the largest irregularly shaped objects in the Solar System.

Like Spaceman Spiff, I love the weirdness we sometimes find when we explore the Universe. Symmetry appeals to the eye—we often find symmetrical objects more beautiful, for whatever reason—but weirdness? That can appeal to the mind, especially if it involves mystery. Take, for example, my favorite of the Solar System moons, Saturn’s odd potato-shaped satellite Hyperion. While it’s not a huge moon—only about 360 kilometers along its largest axis—it stands as one of the largest irregularly shaped bodies in the Solar System. As I mentioned last week when talking about Methone, gravity tends to make objects spherical, while rotation tends to flatten them out. That’s why Earth is mostly spherical, but still bulges at its equator.

For a relatively large body like Hyperion to be irregular, it has to have an interesting history. To drive that point home, consider the moon’s structure: like many of Saturn’s moons, Hyperion is composed largely of water ice, but it’s a lot less dense than that: about half the density of liquid water! The only way for that to happen is if the moon has a lot of empty space, which its appearance also suggests. Perhaps Hyperion experienced a violent collision early in its history, exploding it out like a kernel of popcorn, and leaving it tumbling chaotically.

For Spaceman Spiff, weirdness is its own reward. To me, the weirdness of Hyperion inspires wonder and thought.

(I wrote a longer post about Hyperion last year, if you want to read a little more.)

3 responses to “My Favorite Moon (Science Advent 9)”

  1. My favorite Dan Simmons’.

  2. […] will not apologize for the love I’m giving Saturn’s moons this month. Thanks to the Cassini probe, we are learning so […]

  3. Do not forget the Saturniinae Moon Moth.

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