Fig. 3: The X-ray diffraction (XRD) measurements of Chang’E-5 lunar soil samples and Raman spectra analysis of Chang’E-5 apatite grains in the polished sections.
From: Evidence of water on the lunar surface from Chang’E-5 in-situ spectra and returned samples
a Identification of apatite in lunar soil samples by matching XRD features with the mineral powder diffraction files (PDF) of the International Center for Diffraction Data (ICDD). There are two kinds of crystal structures in apatite: P63/m and P21/b, and the crystal structure of apatite identified in the lunar soils is P63/m. The gray dashed lines show the diffraction peaks of lunar soils matching result with the standard apatite mineral features of the three crystal planes (211), (112), and (202), and the diffraction pattern of the standard apatite mineral (PDF01-080-7126) has been (h00) preferred orientation corrected. b The Raman spectra of different apatite grains in the polished sections. The apatite formulas shown in the figure is derived from the corresponding electron-probe micro-analysis (EPMA) results. We infer that the Raman peak shifts toward 962 cm−1 as the proportion of OH in the apatite grains increased. Part of the Raman measurement positions are marked in Fig. 2c.
