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Emily LakdawallaMarch 20, 2008

When Titan's Winds Blow, Mountains Move

I'm particularly proud of the melodramatic title I came up with for this news story: "When Titan's Winds Blow, Mountains Move." Most news outlets are reporting the major news from this story as being that Titan has an ocean. It's true that this study is important for providing empirical evidence that Titan has an ocean, but the fact that it does wouldn't be a huge surprise to anybody who studies the moons of the outer solar system. The news here is that Titan's crust doesn't rotate synchronously -- it's totally decoupled from the interior, sliding around on that subsurface liquid ocean. The ocean acts as a lubricant, separating the solid core physically from the solid crust, so you have the whole spherical shell of the solid crust able to move separately from the interior. It's mind-boggling to think of the whole crust of a planet-sized world sliding around separately from its core. This has actually been proposed to happen for many places in the solar system, to explain things like polar wander, but on Titan it apparently happens really fast. Usually, geophysicists employ gravitational or tidal torques to explain this kind of crustal motion. But on Titan, the atmosphere is such a heavy hitter that its motion can actually blow the crust around by enough that Cassini was able to observe the crust move away from the simplistically predicted rotation rate by tens of kilometers over only 20 months. Wow.

Many thanks to several scientists at different institutions who answered their phones and took the time to explain the story to me so I could post it so quickly!

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Emily Lakdawalla

Solar System Specialist for The Planetary Society
Read more articles by Emily Lakdawalla

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