The Distribution of Peak-Ring Basins on Mercury and Their Correlation With the High-Mg/Si Terrane

A catalog of mercurian craters that retain their central peak or peak-ring structure was created to aid target prioritization for the Mercury Imaging X-ray Spectrometer (MIXS), now on its way to Mercury aboard BepiColombo. Preliminary analysis of the MIXS crater catalog suggested a potential spatial correlation between an abnormally high spatial density of peak-ring basins and a region of Mercury with elevated Mg/Si values (High-Magnesium Terrane [HMT]). Robust statistical analysis of previously published crater catalogs confirmed that the spatial correlation exists, with an overall confidence level of 97.7%, specifically between peak-ring basins and the HMT, delineated by a contour of Mg/Si = mean + 2σ = 0.648. Applying empirical impact cratering scaling laws to the 15 basins intersecting the HMT suggested that all have excavated material from ~13 to 20 km depth. None of the basins excavated mantle material, predicting instead that deep crustal material contains elevated Mg/Si material. However, five of the basins are predicted to have melted underlying mantle material, which might be a contributing factor in the elevated Mg/Si signature. In the absence of resolvable volcanic features associated with the rise of basaltic melts from the mantle, we favor excavation of deep crustal, high Mg/Si material. MIXS-T is capable of spatially resolving individual features associated with peak-ring basins and it is proposed that the 15 basins within the HMT are prioritized targets for MIXS, to test the hypothesis of exposed deep-crustal material.