Surface Geology and Tectonism on Enceladus

Abstract

Enceladus is remarkable not only for its active water ice eruptions near the south pole, but also because its surface geology preserves a system of large-scale tectonic patterns that record past, as well as present centers of tectonic deformation. The currently active South Polar Terrain (SPT) geological province defines a characteristic tectonic style, geometry, and size scale: It is a crudely circular, kilometer-deep topographic depression that subtends ~70?? in arc and is bounded by a circumpolar chain of south facing arcuate scarps and kilometer-scale mountain belts. Nearer its center, ongoing water ice eruptions emanate from a series of ~200 km-long quasi-parallel rifts, called "tiger-stripes" that have an average spacing of 32 km. Surface locations of ancient, now inactive tectonic provinces similar to the SPT are recorded on the trailing side of Enceladus by the similar geological patterns, geometry, and size-scales of two other tectonically disrupted provinces; Sarandib Planitia (4?N, 298?W) and Diyar Planitia (0?N, 240?W). These regions may record the locations of ancient diapirs that have dissipated or perhaps the progressive migration of a single warm diapir to the south pole of Enceladus as suggested by Nimmo and Pappalardo (Nature 441, 614-616).