Abstract | Impact basins have a significant role in modifying Mercury’s surface, notably through the redistribution of material. They provide access to vertical heterogeneities in the crust and allow the sampling of deep units such as the ancient graphite crust of Low Reflectance Material (LRM) buried under the volcanic resurfacing (Klima et al., 2018). However, impact basins and large craters can also be modified after their formation by the emplacement of younger layers. It appears that several impact basins are filled with a smooth, volcanic in origin, High-reflectance Red Plains (HRP). Moreover, some basins are surrounded by a smooth Low-reflectance Blue Plain (LBP) for which the origin is still uncertain between impact melt or volcanism (Whitten et al., 2015; Rothery et al., 2017). This work presents a study of 4 impact basins currently showing HRP, LBP and LRM. We aim to understand whether their actual similarities are due to the initial composition of their location area or whether there is a common process to their formation independent of the location at the surface.
We mapped HRP, LBP and LRM units using multispectral images obtained by the Mercury Dual Imaging System (MDIS) and spectral observations acquired by the Mercury Atmospheric and Surface composition Spectrometer (MASCS) onboard MESSENGER. MASCS/VIRS data used in this present work are contained in the Mercury Surface Spectroscopy (MeSS) database (this conference Munoz et al 2022 and Cornet et al., 2022). The sampling and spectral characterization of HRP and LBP have been performed within the Caloris basin (this conference Doressoundiram et al., 2022). The LRM was in turn sampled around the Rachmaninoff Basin which is considered to be the most visible, carbon rich and least altered LRM deposit (Klima et al., 2018). A statistical study of the sampled areas allows to obtain a spectral characterization for each of the HRP, LBP and LRM units. This characterization was then used to map the different units interacting in our basins’ study.
This study reveals a similarity in the distribution of spectral units associated with impact basins showing a trend according to their size and age. We propose that the formation of spectral units in and around impact basins on Mercury is a common process resulting in different final appearance depending on the basins. The current appearance of basins would be more related to their age and size rather than to the location on the surface.
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