On the Effect of Magnetospheric Shielding on the Lunar Hydrogen Cycle

The global distribution of surficial hydroxyl on the Moon is hypothesized to be derived from implantation solar wind protons. As traverses geomagnetic tail, it generally shielded wind; therefore, concentration hydrogen expected decrease during full Moon. A Monte Carlo approach used model diffusion implanted atoms in regolith as they form metastable bonds with O atoms, and subsequent degassing H2 into exosphere. We quantify change surface OH exosphere using averaged SW proton flux obtained Acceleration, Reconnection, Turbulence, Electrodynamics Moon's Interaction Sun (ARTEMIS) measurements. At lunar local noon, there a small difference <?10 ppm between concentrations tail compared out. However, cumulative effect traversing magnetotail depleted by ?60 for region that spends most its time wake (waning gibbous waxing crescent) nightside periods when exposed unperturbed wind. decreased approximately an order magnitude while due flux. results are consistent preliminary exospheric observations both (Lyman Alpha Mapping Project Lunar Reconnaissance Orbiter) LAMP mass spectrometer measurements Chandrayaan-I Altitudinal Composition Explorer (CHACE).