Mercury's geodynamic and tectonic history

Abstract

Mercury’s geodynamic evolution has been characterized by a long history of global contraction in response to interior cooling and inner core growth [1]. A record of this history is preserved in the form of a global population of compressional landforms, including lobate scarps, high-relief ridges, and wrinkle ridges [2,3]. Different interpretations of Mercury’s tectonic record led to distinct contraction estimates of <2 km [2] or up to 7 km [3]. Proponents of the large contraction interpretation consider all tectonic landforms, including wrinkle ridges, as lithosphere-scale faults activated by global planetary contraction, while other interpret wrinkle ridges as thin-skinned structures that do not reflect global contraction. In addition, studies commonly use displacement-length ratios to estimate global contraction. However, it is unclear whether such approach can adequately infer global contraction from tectonic databases that are subject to ridge segmentation and where the shortening associated with individual faults might be overestimated with the mapping of secondary ridges [2]. A further key outstanding question is to what extent strain from deformation of the lithosphere contributes to the tectonic record.

Here, we revisit Mercury’s tectonic record using a global tectonic database [4] together with machine learning to evaluate tectonic strain. We then invert observed gravity and topography to estimate how lithospheric deformation contribute to the tectonic record.