AN YIN’S LEGACY: THE TECTONICS OF ENCELADUS’S SOUTH POLAR TERRAIN (Invited Presentation)

An Yin was a creative and innovative thinker who applied terrestrial structural geology expertise to problems in planetary science. The icy moons of the outer solar system display a rich array of geological structures with little erosion, providing the ideal opportunity to apply such skill. Our key collaboration in this area was on the tectonic style and evolution of the South Polar Terrain (SPT) of Enceladus (Yin and Pappalardo, Icarus 260, 409–439, 2015). In this model, SPT is inferred to be bounded by right-slip, left-slip, extensional, and contractional zones on its four edges, accommodating SPT translation as a single sheet. Internal SPT deformation is expressed by distributed right-slip shear, facilitated by left-slip bookshelf-style faulting along the sub-parallel tiger stripe fractures. The SPT transport direction is parallel to the regional topographic gradient, implying gravity-driven motion. The flow-like tectonics across the Enceladus SPT can be explained by the occurrence of a transient thermal event, which allowed the release of gravitational potential energy via lateral viscous flow within the thermally weakened ice shell. In this presentation, I will describe the inferred geology of the Enceladus SPT, while demonstrating the keen structural geological insights that An Yin brought to this topic.