Why is the recent finding of folds on Europa significant?
It’s impossible to fully understand the geology of Europa (or any icy satellite) until we understand the nature of its extension and compression. If there are only extensional features, then it could mean the whole satellite has expanded. If so, this would have important ramifications for the satellite interior. Or if the satellite has subduction zones, then this would be a way for the satellite to cycle surface material into the interior. Understanding the nature of compressional features tells us (in part) how the icy crust is recycled–we know that new material comes up to the surface to form the plentiful dark bands (extensional features), and now we believe that some (though not all) of the extension is taken up by making folds, which can cycle some shallow subsurface material back into the deeper subsurface. Some other icy satellites show large ridges, and some have been suggested to be folds (e.g. on Enceladus and Dione at Saturn), but no unique and convincing evidence of folds
