Keywords:Earth wind, Lunar water, Solar wind
The evidences for lunar water (e.g., polar ice and OH-/H2O) have been discovered in recent lunar missions. The dynamic lunar hydration/dehydration cycle over a lunar day and the suppression of lunar water within lunar magnetic anomalies indicated that solar wind proton should be an important source of lunar surface water. However, the Moon passes through its surrounding plasma environment comprised of solar wind, magnetosheath, and magnetotail. Therefore, the dependence of lunar water content on plasma parameter remains further deep investigations. In this study, we try to find the relevance between the variability of lunar water and lunar plasma environment based on the observations from the Kaguya MAP-PACE and Chandrayaan-1 M3 spectrometer. We first study lunar hydration inside/outside the magnetosphere using the M3 spectral data, from which it is unexpectedly found that the polar surficial OH/H2O abundance remains the same level when in the solar wind and in the magnetosphere. We suggest that the particles from the magnetosphere (Earth wind, naturally different from solar wind) contribute to lunar hydration. And then we studied lunar hydration inside/outside the plasma sheet, in which the proton has a broad velocity distribution with a wide thermal spread. A case study shows that the water content at the same region on the Moon is different when in the plasma sheet and in the lobe of Earth’s magnetotail. Nevertheless, more work is needed to understand the physical mechanism.