Evolution of the Mercurian Crust as Recorded in Carbon

Abstract Mercury and other silicate bodies are essential for understanding planetary formation and evolution. The surface of Mercury is unique and enigmatic, yet this innermost planet remains the least explored. The crust exhibits relatively low reflectance, possibly due to the excavation of a buried, primary flotation crust enriched in graphite. The combined spectral ranges of the Mariner 10 vidicon cameras and the MESSENGER Mercury Dual Imaging System (MDIS) characterize a diagnostic reflectance feature of graphitic materials, allowing us to test for their surface presence. We geometrically controlled Mariner 10 images to an MDIS-based control network, achieving subpixel registration between the image sets. With this combined dataset, ratio image mosaics and reflectance measurements comparing ultraviolet (UV) to visible and near-infrared wavelengths are consistent with increased UV reflectance in low-reflectance material, which fades with mixing and maturity. We conclude that space weathering processes mix graphite into the surrounding regolith and may alter it to other carbon phases.