Understanding Compositional Evolution of Hollows at Dominici Crater on Mercury

We investigate the composition of hollows across their devolatilization phases at Dominici crater on Mercury. Utilizing machine learning on Mercury Dual Imaging System data, we delineated surface units at the area and extracted their reflectance spectra. We applied spectral modeling to laboratory sulfides, chlorides, graphite, and silicate minerals spectra to estimate the compositions of hollows and their background terrains. Active hollow at the crater rim/wall predominantly comprises of CaS, MgS, and silicates, with a trace amount of graphite. In contrast, waning hollows at the crater center contain slightly lower amounts of sulfides and silicates, but higher levels of graphite than active hollows. The nearby background terrains in low reflectance materials (LRM) are enriched in graphite and MgS, contributing to their darker appearance, alongside a lower concentration of silicates. We suggest that hollow formation initiates from the loss of sulfides (primarily MgS and CaS) and some graphite. As devolatilization comes to an end, a mixture predominantly of silicate minerals remains in the hollows— impeding further vertical growth.