Fig. 1. Raman characteristic bands of minerals in lunar soil simulants

Fig. 2. Raman spectral features of water in high wavenumber region（2 600-3 900 cm^-1）in hydrated samples：（a）broad envelope characteristic peak；（b）non-hydrogen bonded hydroxyl characteristic peak；（c）mixed mode peak

Fig. 3. Raman spectral features of adsorbed water，crystalline water，hydroxyl water，and ice in Lunar soil simulant：（a）liquid adsorbed water；（b）magnesium sulfate heptahydrate crystalline water；（c）Kaolinite hydroxyl water；（d）ice

Fig. 4. Relationship between peak area and water content of three water forms in lunar soil simulants：（a）relationship between peak area and water content；（b）relationship between peak area peak normalized and water content；（c）estimation of water detection limit

Fig. 5. Changes and comparison of Raman peaks with water content in different matrices（olivine and pyroxene）：（a）Raman peaks of olivine and liquid water；（b）Raman peaks of pyroxene and liquid water；（c）comparison of water-containing Raman peaks in two matrices；（d）relationship between peak intensity and water content

Fig. 6. Changes in Raman spectra of pyroxene with adsorbed water over evaporation time

Fig. 7. Inversion of water content in lunar soil simulanta by three regression models：（a）RR；（b）PLSR；（c）LR；（d）determination of optimal regularization parameter in RR；（e）determination of optimal number of principal components in PLSR