Nature: The tectonic patterns and stress history of Europa are exceedingly complex and many large-scale features remain unexplained. Now Paul Schenk, Isamu Matsuyama & Francis Nimmo in this week's Nature have mapped troughs and depressions on Europa that indicate some features are caused by 'true polar wander'. In other words, they discovered that by re-orientating Europa's floating outer ice shell about Jupiter's tidal axis, and treating the surface as totally decoupled from any rocky interior mass, the tidal forces place on this shell by Jupiter's gravitational pull induce stress fractures seen on the surface of the moon.

These depressions also appear to be geographically related to other large-scale bright and dark lineaments4, 5, suggesting that many of Europa's tectonic patterns may also be related to true polar wander.