26 July 2009

Weirder than I can imagine

I've been staring at this image off and on all day.

Titan's surface—all of it—moves. ("We had an erroneous spin model.")

The best available explanation of this is that Titan's cryo-geology, where water is a rock, leads to a large liquid water layer, decoupling the upper crust from the rest of the moon. (Earth has the Moho, where rock stops being a solid and the plates slide on the upper mantle, but this is one of the places where the parallels between terrestrial and Titanian geology break down, since water is way less viscous than molten rock.) This isn't news, it was published more than a year ago now.

The image? Various outer-system bodies—Galilean moons of Jupiter, Titan, Neptunean ice-moons, Sedna, Eris, and Pluto—all hypothesized to have liquid-water layers. Europa's is apparently relatively small, it's just under much less ice crust.

So this whole decoupled surface, the outer crust just rotates on its own thing, might well be relatively common. (Never mind the whole "liquid water in Pluto" thing. It's more like an aqueous mantle, I can keep that from melting my brain.) It's the notion of gyroscope planets, the outer shell spinning freely on a water bearing over the rocky core, that's really messing with my head. What happens if you lay equatorial cables and stick up lots and lots of shiny-one-side, black-the-other fins? Can you run a dwarf planet as a generator?

And certain parties wonder why there's so little solar-system science fiction being written.

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