Fig. 2: Relationships of Spallation-corrected δD values with H₂O contents for the lunar soils.

The results for ilmenite rims in this work are plotted to compare with literature data for olivine, pyroxene, plagioclase, and ilmenite returned by the Apollo and CE5 missions^8,9,25,34. The lunar mantle⁸¹ is also shown for comparison. The SW endmember is inferred to have extremely low δD value (~−997‰; ref. ⁵³). The H isotopic variation can be classified into two categories³⁴, i.e. samples with δD values < −400‰ contains major contribution from SW implantation, where those with δD values > −400‰ are associated with other reservoirs, such as lunar interior, carbonaceous chondrites (CCs) and comets^21,23. All analyzed ilmenite samples in this work, as well as one ilmenite from the literature, show the δD values < −400‰. The black line represents the binary mixing between the pure solar component (H₂O = 12,000 ppm, δD = −950‰) and the indigenous water reservoir of the Moon (H₂O = 100 ppm, δD = 0‰) reservoir of the Moon. Outgassing of H-bearing phases from the minerals into space is also modeled and shown in dashed lines with different colors, i.e., pink for H, green for H₂, and blue for H₂O (see “Methods” section for details). The error bars represent 1σ uncertainty, and some error bars for samples are within the size of the symbol. The silicate minerals and ilmenites are outlined with different colors, and although they overlap with each other, the silicate phases can have a much higher water content and a lower δD range, forming two distinct clusters. It is noted that the seemingly slight positive correlation observed in the ilmenite data appears to be dominated by two (outlier) data points. The data from this study is provided in Supplementary Table 1.