Seminar by Sébastien Verkercke, Laboratoire de Physique des Plasmas / École Polytechnique / Centre National d'Etudes Spatiales
Airless bodies of the Solar System have their surfaces unprotected from external forcing by the Sun and space. In the case of Mercury or the Moon, their surfaces are continuously bombarded by the solar wind and micro-meteoroids. Over time, these impacts have damaged the surface, and fractured the ground into fine grains, covering these bodies with a porous layer of silicate grains. This structure affects the weathering of such bodies, influencing the ejection of surface atoms that form the exosphere around these bodies. The adsorption of exospheric volatiles on the Moon and Mercury are also affected by the regolith structure, composition, and temperature. This highlights the importance of the surface micro-structure and composition in the surface-exosphere-magnetosphere interactions. My research aims to understand the effects induced by the surface on the exosphere and magnetosphere, and the feedback these systems have on the Hermean regolith, using both numerical models and spacecraft data. A great example of this is the unexplained observations by MESSENGER of Mercury’s sodium exosphere. Using a multi-scale approach, going from atomic interactions to planetary exospheric transport, our model reproduces the yearly variability of Mercury’s exosphere and reconciles theory with observations. As the neutral exosphere is the source of the magnetospheric ions, this model helps prepare for the interpretation of future observations obtained by Mass Spectrum Analyzer on board BepiColombo.
Host: Daniel Wolf Savin