Tidally Driven Failure Along Europa's Rhadamanthys Linea

The surface of Europa is crosscut by a dense network of fractures and there are many candidate faults for studying past tectonic activity. To better understand the role of tidal stress sources and implications for faulting on Europa, we investigate the relationship between shear and normal stresses at Rhadamanthys Linea, a northwest oriented fracture in the northern hemisphere. Previous work on Agenor Linea, a right-lateral strike-slip fracture in the southern hemisphere, suggests that both tidal diurnal and non-synchronous rotation (NSR) stresses play a critical role in the mechanics of Coulomb shear failure on Europa. At Agenor Linea, shear failure from diurnal tidal stress mechanisms is difficult to achieve because the relatively large over¬burden stress (ie., 1.2 MPa at 1 km depth) dominates the stress field; however, MPa order stresses from NSR permit right-lateral shear failure along the west side of the fault at shallow depths (< 3 km) and along the east side of the fault at 3 - 4 km depths. Much like Agenor Linea, our new results for Rhadamanthys Linea, using a combined diurnal and NSR stress model, indicate that shear failure occurs along the west side of the fracture at shallow depths (< 2 km) and along the east side at 2 - 3 km depths. These results assume a constant coefficient of friction of 0.6; a reduced frictional coefficient would permit shear failure to propagate to slightly deeper depths. Our results also imply that Rhadamanthys Linea has a left-lateral sense of slip, which is further supported by global stress calculations and photogeologic evidence. Tidally driven failure parameters and sense of slip for additional structures like Astypalea Linea and Conamara Chaos will also be investigated, offering a unique comparison of geologic activity of fractures residing in geographically diverse locations of Europa.