2026/02/18 by Romain Canu-Blot, Martin Wieser, Umberto Rollero +6 · 1 voice
Engineering · Mathematics · Physics and Astronomy · #Astro and Planetary Science #Hydrogen #Ion #Ion-surface interactions and analysis #Planetary Science and Exploration #Regolith #Scattering #Solar wind #Sputtering #physics.atom-ph #physics.ins-det #physics.space-ph #stat.AP
paper · pdf · open access · doi:10.1051/0004-6361/202659499
published in Astronomy and Astrophysics 710, A182 (EDP Sciences)
arxiv published 2026/02/18 · arxiv updated 2026/02/18 · openalex publication_date 2026/05/06 · openalex created_date 2026/05/07 · openalex updated_date 2026/08/01
Context . Airless planetary bodies are directly exposed to solar wind ions, which can scatter or become implanted upon impact with the regolith-covered surface, while also sputtering surface atoms. Aims . We constructed a semi-analytical model for the scattering of ions of hundreds of electron volts (eV) and the sputtering of surface atoms, both resulting in the emission of negative ions from the lunar surface. Our model contains a novel description of the scattering process that is physics-based and constrained by observations. Methods . We used data from the Negative Ions at the Lunar Surface (NILS) instrument on the Chang’e-6 lander to update prior knowledge of ion scattering and sputtering from lunar regolith through Bayesian inference. Results . Our model shows a good agreement with the NILS data. We find that a precipitating solar wind proton has a roughly 22 −6.1 +4.9 % chance of scattering from the lunar surface in any charge state and 8.1 −3.9 +7.9 % chance of sputtering a surface hydrogen atom. The resulting ratio of scattered to sputtered hydrogen flux is η sc /η sp = 1.5 −1.1 +1.5 for a proton speed of 300 km/s. We found a high probability (7-20%) that a hydrogen atom leaves the surface negatively charged. The angular emission distributions at near-grazing angles for both scattered and sputtered fluxes are controlled by surface roughness. Our model also indicates significant inelastic energy losses for hydrogen interacting with the regolith, suggesting a longer effective path length than previously assumed. Finally, we estimated a surface binding energy of 5.5 eV, consistent with the observations. Conclusions . Our model describes the scattering and sputtering of particles of any charge state from any homogeneous, multi-species surface. Using NILS data, we successfully applied the model to update our understanding of solar wind interacting with lunar regolith and the emission of negative hydrogen ions.