Laboratory simulation of ion impact and back-scattering on Mercury surface analogues for planetary space weather investigation

Mercury has a surface-bound exosphere that mediates transport of ion and netural species on the surface and within the Hermean environment. When precipitating solar wind particles impact the planet’s regolith, ions may be neutralised and backscattered, form chemical reactions with surface species, or induce sputtering processes. The SERENA (Search for Exospheric Refilling and Emitted Neutral Abundances) instrument onboard BepiColombo aims to study these surface-exosphere-magnetosphere interactions, using a suite of particle detectors and mass spectrometers. 
At INAF/IAPS, the Ion and Energetic Neutral Atom (I-ENA) laboratory facilitates controlled experiments on the interaction of ion/neutral beams with diverse surface analogues and detectors for planetary space weather investigation. ELENA (Emitted Low Energy and Neutral Atoms) one of the SERENA instruments, is devoted to detect backscattered ENA and possibly magnetospheric and solar wind ions with an energy range of 10 eV-5 keV, and its Flight Spare (FS) is tested and calibrated in the laboratory. The ELENA FS is intended to be used for future investigations of backscattering process with Mercury analogues. Laboratory experiments involving irradiation of Mercury analogues aim to provide ground truth to the data provided by this instrument. 
We present a test for simulating Solar Wind interactions with Mercury surface analogues. Mercury analogues are placed in a bespoke vacuum system which achieves working pressures of 10-7 mbar. A particle beam of energies between 0.5-5 keV (Helium-Argon), that can be modulated in intensity, area and direction, is used to irradiate samples. The charged particle beam (ions) can also be made into a beam of ENA with a neutralisation cell for charge exchange effect. 
We plan to investigate a variety of diverse samples, including slabs of meteorite and pellets similar in composition and grain size to Mercury’s surface.
This work will provide a detailed description of the facility and experimental framework, while identifying open questions and fostering discussions on interdisciplinary collaborations needed to advance Mercury science. Such experiments are pivotal for improving our understanding of Mercury’s environment and directly support the goals of the BepiColombo mission.