Distribution of large-scale contractional tectonic landforms on Mercury: Implications for the origin of global stresses

The surface of Mercury is dominated by contractional tectonic landforms that are evidence of global-scale crustal deformation. Using MESSENGER orbital high-incidence angle imaging and topographic data, large-scale lobate thrust fault scarps have been mapped globally. The spatial distribution and areal density of the contractional landforms are not uniform; concentrations occur in longitudinal bands and between the north and south hemispheres. Their orientations are generally north-south at low latitude to midlatitude and east-west at high latitudes. The spatial distribution and distribution of orientations of these large-scale contractional features suggest that planet-wide contraction due to interior cooling cannot be the sole source of global stresses. The nonrandom orientations are best explained by a combination of stresses from global contraction and tidal despinning combined with an equator-to-pole variation in lithospheric thickness, while the nonuniform areal density of the contractional features may indicate the influence of mantle downwelling or heterogeneities in lithospheric strength.