Backscattered and sputtered atoms and ions in the near surface environment of the Moon

Solar wind protons precipitating onto the lunar regolith result in backscattering and sputtering of surface atoms. Emitted particles are a source for the lunar  exosphere. The interaction between precipitating solar wind and the surface does not conserve the charge state, thus positive [1] and negative [2] ions as well as energetic neutral atoms are emitted[3]. We combine data from recent measurements on the lunar surface by the NILS instrument[4] on Chang’e-6 and the ASAN instrument[5] on Chang’e-4, with data measured from orbit by Artemis[6] and Chandrayaan-1 [7]  to investigate the full charge state distribution of emitted hydrogen. We discuss the fate of the different observed particle populations and their effect on in the near lunar environment.[1] Saito, Y., et al., (2008). Solar wind proton reflection at the lunar surface: Low energy ion measurement by MAP-PACE onboard SELENE (KAGUYA). Geophys. Res. Lett., doi:10.1029/2008GL036077.[2] Wieser, M., et. al, (2025). Direct observations of negative ions on the Lunar surface by Chang’E-6. Communications Earth & Environment, doi: 10.1038/s43247-025-02399-7.[3] Wieser, M., et al.,(2009). Extremely high reflection of solar wind protons as neutral hydro- gen atoms from regolith in space. Planetary and Space Science. doi: 10.1016/j.pss.2009.09.012.[4] R. Canu-Blot, et al. (2025), The Negative Ions at the Lunar Surface (NILS) Instrument on the Chang’E-6 Mission. Space Science Reviews, doi:10.1007/s11214-025-01162-w[5] M. Wieser, et al. (2020), The Advanced Small Analyzer for Neutrals (ASAN) on the Chang’E-4 Rover Yutu-2. Space Science Reviews, doi:10.1007/s11214-020-00691-w[6] C. Lue, et al.,(2018), Artemis observations of solar wind proton scattering off the lunar surface. Journal of Geophysical Research: Space Physics, doi:10.1029/2018JA025486[7] Barabash, S., et al., (2009). Investigation of the solar wind–Moon interaction onboard Chandrayaan-1 mission with the SARA experiment. Current Science, 96(4):526–532.