Abstract | Models based on gravity and topography data suggest the existence of significant large-scale variations in the thickness of Mercury’s crust. In particular, models that use the surface mineralogy to guide the choice of the crustal density predict that the so-called high-Mg region is underlain by a thick crustal root resulting from a high-degree of partial melting (Beuthe et al., GRL, 2020). Numerical simulations using a constant surface temperature, however, predict that convection in Mercury’s thin mantle is characterized by a laterally-uniform pattern of small-scale up- and downwellings, with nearly unitary aspect ratio (Tosi et al., JGR, 2013). While the overall amount of crust produced in these models compares favorably with estimates of the average crustal thickness, the lateral distribution of crust reflects the convection pattern and is thus difficult to reconcile with the large-scale variations inferred from the remote-sensing data. Lateral variations in surface temperature due to uneven insolation can induce long-wavelength variations of the mantle temperature at depth and in turn affect the generation of partial melt. We use 3D simulations of the thermo-chemical evolution of Mercury to investigate the influence of insolation on the production of Mercury’s crust. We test the insolation associated with the present-day 3:2 resonance, as well as with other resonances (1:1 and 2:1) and eccentricities that may have characterized the orbit of Mercury before the capture into its current state. The insolations associated with the 3:2 and 2:1 resonances have a relatively small influence on crust formation. By contrast, the surface temperature distribution resulting from synchronous resonance induces a significant heating of the deep mantle beneath the dayside that causes the formation of large-scale crustal thickness variations. This scenario could contribute to explain the high-degree of melting and large thickness of the crust inferred for the high-Mg region. |
