Mercury has multiple, superposed global tectonic patterns

Abstract

There is a long tradition in studying tectonic landforms on Mercury, as it hosts myriad structures accommodating both shortening and extension. These landforms have been extensively studied in terms of size, distribution, and age, and many tectonic maps have been produced. The orientations of fault-related landforms were previously studied for subsets of structures, but a detailed global investigation of orientations for all tectonic landforms on Mercury has yet to be carried out. Variations in orientations of tectonic structures across the globe can provide insights into the tectonic processes that formed them. We compile a global tectonic map that contains 18,541 structures specified as shortening landforms, extensional landforms, or troughs. We process the map data to extract fault orientations in three different geographic configurations with radial and concentric bins around the rotational poles, the Caloris basin, and the hot poles. In each of these three representations, we find systematic tectonic patterns that, taken together, show multiple, superposed preferred orientations of faults. In particular, systematic thrust fault orientations radial and concentric to the Caloris basin are detected on the hemispheric scale, revealing an enormous impact damage zone where fractures were reactivated by later tectonic processes. Furthermore, faults display systematic orientations around the hot poles, showing that tectonic processes or lithospheric strength and thickness variations arising from Mercury's spin–orbit resonance with the Sun have played a role in its tectonic history.