Evidence of water on the lunar surface from Chang'E-5 in-situ spectra and returned samples

The distribution range, time-varying characteristics, and sources of lunar water are still controversial. Here we show the Chang'E-5 in-situ spectral observations of lunar water under Earth's magnetosphere shielding and relatively high temperatures. Our results show the hydroxyl contents of lunar soils in Chang'E-5 landing site are with a mean value of 28.5 ppm, which is on the weak end of lunar hydration features. This is consistent with the predictions from remote sensing and ground-based telescopic data. Laboratory analysis of the Chang'E-5 returned samples also provide critical clues to the possible sources of these hydroxyl contents. Much less agglutinate glass contents suggest a weak contribution of solar wind implantation. Besides, the apatite present in the samples can provide hydroxyl contents in the range of 0 to 179 ± 13 ppm, which shows compelling evidence that, the hydroxyl-containing apatite may be an important source for the excess hydroxyl observed at this young mare region.

Jianjun Liu, Bin Liu, Xin Ren, Chunlai Li, Rong Shu, Lin Guo, Songzheng Yu, Qin Zhou, Dawei Liu, Xingguo Zeng, Xingye Gao, Guangliang Zhang, Wei Yan, Hongbo Zhang, Lihui Jia, Shifeng Jin, Chunhua Xu, Xiangjin Deng, Jianfeng Xie, Jianfeng Yang, Changning Huang, Wei Zuo, Yan Su, Weibin Wen, Ziyuan Ouyang