Kinematics of Plate Rotation on Europa: Case study in Argadnel Regio

Results of recent tectonic reconstructions on the Galilean moon, Europa, have displayed plate-like motions and rotation. Visual analysis of an area in Argadnel Regio suggests similar tectonic behavior in Europa’s past with a significant amount of rotation. These rotations appear to be analogous to kinematic behavior of rotating terrestrial microplates. Plate rotation in Argadnel Regio may be driven by either of two mechanisms: subsurface shear flow (i.e. originating from convective forces) or lateral forcing from bounding plates (e.g. edge-driven). The location of the instantaneous axes of rotation (IAR), the axis that passes through the point of instantaneous zero velocity, can be used to assess the driving mechanism of plate rotation. IARs located on the boundary of a rotating plate suggest laterally forced rotation. IARs located away from plate boundaries are indicative of rotation driven by shear flow at the interface of the lithosphere and asthenosphere. The hypothesis motivating the work presented here is that rotation in Argadnel Regio is driven by shear flow within the ice shell. This hypothesis is tested by measuring locations of IARs on Galileo Solid State Imaging Camera images of Argadnel Regio. Cross-cutting relationships were examined to obtain the sequence of plate motions to reconstruct section of Argadnel Regio using GPlates. The reconstruction was used to extrapolate locations of IARs for a circular feature (CF) composed of a group of plates that rotated collectively ~ 40°. IARs detected away from plate boundaries of the CF suggest that rotation was due to shear flow within the ice shell. However, the IARs associated with two plates in the interior of the CF found on plate boundaries suggest that some “edge-driven” forces are responsible for the rotation and rotation related deformation due to location of IARs on plate boundaries. A plate bordering the (CF) appears to be completely “edge-driven” by the rotation of CF due to the detection of IARs on the plate boundary. These results suggest that rotation in Argadnel Regio was driven from edge-driven forces and forces originating in the subsurface. The detection of convective driven tectonics makes Argadnel Regio a landing site candidate for future missions.