ANTARCTIC ANALOG FOR DILATIONAL BANDS ON EUROPA (Invited Presentation)

Europa’s surface shows signs of extension, which is revealed as lithospheric dilation expressed along ridges, dilational bands and ridged bands. Ridges, the most common tectonic feature on Europa, comprise a central crack flanked by two raised banks a few hundred meters high and each side. Ridges are thought to form along tensile cracks within the ice shell. Dilational bands are usually topographically lower and wider than ridges and display a smooth lineated interior. Some lineaments, ridged bands, have characteristics of both ridges and bands. Together these three classes may represent a continuum of formation in which ridges and dilational bands are end members. A model of ridge formation in which tidal cycling of a crack opens and closes the crack daily, possibly pushing material to the surface and forming a ridge superimposed with a secular dilation of the crack can combine to form the various morphologies described.

We will present this model of ridge and band formation, along with an Earth analog from the Antarctic Ross Ice Shelf. Tensile failures in the Ross Ice Shelf exhibit secular dilation, upon which a tidal signal can be seen. From this analog we conclude that the extension model for Europa may be credible and that the secular dilation is most likely from a regional source and not tidally driven.