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Evidence for a Shift of Europa’s Icy Crust

27 Aug 2020, 13:08 UTC
Evidence for a Shift of Europa’s Icy Crust
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A hypothesis about an astronomical object snaps into sharper detail when it can be tested. Thus the new findings on Europa and the movements of the ice shell that covers its ocean, which are the subject of a paper in Geophysical Research Letters. The work of Paul Schenk (Lunar and Planetary Institute, Houston) and colleagues, the paper argues that the shell has rotated by about 70 degrees during the last several million years. Clearly, such movement can only happen with a shell floating freely over a liquid ocean beneath, and Europa Clipper should be able to tell us more.
Remember, we are talking about a geologically young surface on this Jovian moon, as indicated by, among other things, the relative smoothness of the terrain and the paucity of impact craters. All that is consistent with ice in motion in one way or another. Schenk’s team homes in on large global-scale circular patterns that can be made out by reference to Galileo and Voyager data, previously identified features that could only have been formed during a reorientation of the shell. The process moves the outer shell with respect to the moon’s spin axis, and is known as true polar wander (TPW). ...

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