ENCELADUS'S TECTONIC ACTIVITY IN DEEP TIME

Beyond the geologically active south polar terrains (SPT), Enceladus’s surface can be broadly categorized into the geologically young tectonically resurfaced terrains on the leading and trailing hemispheres (LHT and THT), and the ancient (~4Ga) cratered terrains on the Saturn and anti-Saturn hemispheres. The tectonically resurfaced LHT and THT (~1-2Ga) on Enceladus and the dissection of the Saturn and anti-Saturn cratered terrains by pit chains demonstrate a long, axisymmetric tectonic history. The tectonic resurfacing of the LHT and THT postdate a period of heavy bombardment, removing evidence of cratering and giving way to recent tectonism like pit chain formation and the currently active SPT.

We identify an older group of structures, we term ancient tectonic features, that lie stratigraphically below and therefore predate the ancient cratered terrains. Ancient tectonic features are broad, muted, linear to curvilinear, and typically form in ~10 km long segments. They are identified as ancient based on their almost exclusive occurrence within the cratered terrains and they are crosscut by both pit chains and craters. Ancient tectonic features can be broken up into two primary groups: ancient ridges and ancient troughs.

We present maps of these ancient tectonic features as well as first-order models of global stress fields and attempt to reconstruct the early tectonic activity of Enceladus, prior to the period of heavy bombardment and the formation of the ancient cratered terrains.