Antarctic Rifts as an Analog for Studying Tidal Motions along Cracks on Icy Satellites


Abstract

  • A variety of ridges and dilational bands have been observed on Europa. Double ridges, which are thought to flank a central fracture, are among the most common tectonic features on Europa. While their exact formation mechanism remains a mystery, cyclic motion of the central fracture, induced by tidal stresses, likely plays a role in their development. If regional tension is applied to a fault that is undergoing cyclic tidal motions, other more complex tectonic systems may form. The different observed morphologies of ridges and bands may thus depend on the rate of regional expansion relative to the tidal timescale. Regional expansion that is much faster than the ridge formation timescale would likely produce a smooth dilational band because ridges would not have time to form as the fracture was being pulled apart. Ridged bands, on the other hand, display parallel ridge structures. This type of band may form as a result of expansion that occurred on a timescale commensurate with the ridge formation timescale, allowing new ridge pairs to form throughout the dilation process. Together these three classes of tectonic features may represent a continuum of formation in which ridges and dilational bands are end members. Ross Ice Shelf, Antarctica, represents an Earth analog for the interaction of regional dilation and tidal motion and may provide insight to the model proposed for Europa. Tensile failures near the front of the Ross Ice Shelf exhibit secular dilation, upon which a tidal working of the rift can be observed. From this analog we conclude that the extension model for Europa may be credible and that the secular dilation is driven mainly by a regional source. Wedging of the rift apart by its infill material drives a second source of dilation. We will present an overview on Europa and its observed morphologies. We will also present an overview on Antarctic ice shelves and their potential as an analog for further modeling of icy moons.