Reconfiguration of Mercury's Exosphere During Strong Space Weather Events

Abstract Mercury is exposed to various space weathering processes, which alter the surface and cause emission of atoms and molecules into the exosphere. The exosphere thus allows remote insights into the surface composition and erosion processes, with the emission of refractory elements such as Ca and Mg typically being dominated by micrometeoroid‐impact vaporization. Here we present simulations of the enhanced sputtering by ion impacts during interplanetary coronal mass ejections (ICMEs), predicting an exosphere regime change for strong space weather events. Due to higher ion fluxes and erosion of Mercury's dayside magnetosphere, the sputter source increases by up to a factor of 380. As a result, sputtering becomes the dominant release process for Ca and Mg, temporarily causing a reconfiguration from a dawn‐centered, MIV‐dominated exosphere to a dayside‐centered, sputter‐dominated exosphere. Our study thus highlights and quantifies the variability in Mercury's space environment and the system's strong coupling to space weather effects.