Floating

Titan’s surface turns out to be even stranger than we’d imagined:

In a paper to be published in tomorrow’s issue of the journal Science, members of the Cassini RADAR team announce evidence that Saturn’s moon Titan hides an ocean beneath its surface.  The presence of a global ocean means that the entire crust of Titan is “decoupled” from the moon’s interior.  Outside forces acting on Titan’s crust, most importantly the force of the global circulation of the atmosphere, can apparently slide the entire crust around on Titan’s ocean, so that the crust does not rotate at exactly the same rate that the moon orbits Saturn.

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What is making Titan’s surface move?  It’s the wind, says Ralph Lorenz, first author on the Science paper.  Lorenz explained that a pair of atmospheric scientists, Tetsuya Tokano and Fritz Neubauer, had predicted at an American Geophysical Union meeting in 2005 that if Titan had an ocean, the atmosphere could be capable of shoving surface landmarks around by distances of up to 100 kilometers compared with positions predicted from the assumption of a constant rotation rate.  “I thought, ‘Hundreds of kilometers? You’ve got to be kidding,’” Lorenz remembers.  Since each individual RADAR image of Titan is a long “noodle” that is only approximately 200 kilometers wide at its center, employing the wrong assumptions about Titan’s rotation would mean that features on Titan would be very noticeably offset in RADAR images of the same locations taken on different dates, which is exactly what the RADAR team found. [...]