¹E. Caminiti,²S. Besse,³A. Doressoundiram,^4,5J. Wright
Journal of Geophysical Research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2025JE009359]
¹Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), Sagamihara, Japan
²European Space Agency (ESA), European Space Astronomy Center (ESAC), Madrid, Spain
³LIRA, Observatoire deParis, Université PSL, CNRS, Sorbone Université, Université de Paris, Meudon, France
⁴School of Physics and Astronomy, University of Leicester, Leicester, UK,
⁵School of Physical Sciences, The Open University, Milton Keynes, UK
Published by arrangement with John Wiley & Sons

NASA’s MErcury Surface, Space ENvironment, GEochemistry, and Ranging mission hasrevealed that about 27% of the surface of Mercury is covered by smooth plains, which are mostly volcanic inorigin. These plains are mainly located in the northern hemisphere, as well as within and around majorimpact basins. We used Mercury Atmospheric and Surface Composition Spectrometer data to perform anexhaustive spectral analysis of five major impact basins: Caloris, Rembrandt, Beethoven, Tolstoj, andRachmaninoff. We highlighted the existence of a new high‐reflectance spectral unit, that had previously onlybeen identified within the Rembrandt basin, as a major unit being more widespread. We named this new unitYoung High‐reflectance Red Plains. We found a common sequence of volcanic episodes that infilled thebasins and shaped their current surface spectral properties. We have shown that the size of the basin and theage of the volcanic infills are likely important parameters for the layering of different volcanic plains,defining the surface spectral units. Our study gives access to mantle properties, and we suggest thatheterogeneity in the mantle is certainly not necessary to explain the spectral properties of effusive volcanismassociated with impact basins. Future observations by the ESA‐JAXA‐BepiColombo mission are eagerlyawaited to better constrain the planet’s spectral, compositional, morphological, and geophysical surfaceproperties.