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The reporter learned today (23rd) from the Institute of Physics of the Chinese Academy of Sciences that Chen Xiaolong, a researcher at the Beijing National Research Center for Condensed Matter Physics, the Institute of Physics of the Chinese Academy of Sciences, Jin Shifeng, an associate researcher, Hao Munan, a doctoral student, and others, together with Guo Zhongnan, an associate professor at the University of Science and Technology Beijing, Yin Bohao, an engineer at Tianjin University, Ma Yunqi, a researcher at the Qinghai Institute of Salt Lakes of the Chinese Academy of Sciences, and Deng Lijun, an engineer at Zhengzhou University,Among the lunar samples brought back by Chang'e 5, an unknown mineral crystal rich in water molecules and ammonium on the moon, ULM-1, was discovered. This marks the first time that scientists have discovered molecular water in lunar soil, revealing the true existence form of water molecules and ammonium on the moon.The research results were recently published online in the academic journal Nature Astronomy.

Whether there is water on the moon is crucial to lunar evolution research and resource development.Studies of Apollo samples collected between 1969 and 1972 showed that no water-containing minerals were found in the lunar soil.Since then, the basic assumption of lunar science is that the moon does not contain water, which has had an important impact on understanding the evolution of lunar volcanoes, the origin of the moon and the earth. In 1994, researchers observed the lunar poles through the Clementine probe and proposed that water ice may exist in the lunar soil in the permanent shadow areas of the polar regions. In 2009, the lunar mineral mapping spectrometer carried by Chandrayaan-1 found that there were signals of hydroxyl and/or water molecules caused by solar wind on the lunar surface. In the same year, the Lunar Observation and Sensing Satellite hit the permanent shadow area of ​​the moon at a speed of 2.5 km/s, and remote sensing measurements of the impact dust showed signals of water. In recent years, remote sensing data have shown signs of the presence of water molecules in the illuminated areas of the moon.Using highly sensitive characterization techniques, scientists found "water" (H+, OH- or H2O) in some glasses and minerals at levels of one part per million during the Apollo lunar samples collected that year, but there was no conclusive evidence of the existence of water molecules.

The lunar soil samples collected by my country's Chang'e 5 are the youngest basalt and the lunar samples with the highest latitude to date, providing new opportunities for the study of lunar water.The study conducted by Chinese researchers based on single crystal diffraction and chemical analysis found that these lunar water and ammonium appear in the form of a hydrated mineral with the composition of (NH4, K, Cs, Rb)MgCl3·6H2O. The mineral molecular formula contains up to six crystal water, the mass ratio of water molecules in the sample is as high as 41%.The characteristic vibration peaks from water molecules and ammonium can be clearly observed in both infrared and Raman spectra. The charge density of the crystal can clearly see the hydrogen in the water molecule. The crystal structure and composition of ULM-1 are similar to a rare crater mineral discovered on Earth in recent years. On Earth, this mineral is formed by the interaction of hot basalt with volcanic gases rich in water and ammonia.thisforThe sources of water and ammonia on the moon provide new clues.

To ensure the accuracy of this discovery, the study conducted rigorous chemical and chlorine isotope analysis. Nano-secondary ion mass spectrometry data showed that the Cl isotope composition of the mineral was significantly different from that of Earth minerals and consistent with minerals on the moon. The researchers analyzed the chemical composition and formation conditions of the mineral and further ruled out Earth contamination or rocket exhaust as the source of this hydrate. The presence of this hexahydrate mineral provides important constraints on the composition of lunar volcanic gases. Thermodynamic analysis shows that the lower limit of water content in lunar volcanic gases at the time was comparable to that of the current driest Lengai volcano on Earth. This reveals a complex history of lunar volcanic degassing,It is of great significance to explore the evolution process of the moon.

The discovery of this hydrated mineral reveals a possible form of water molecules on the moon - hydrated salt.Unlike volatile water ice, this hydrate is very stable in the high-latitude region of the moon (Chang'e 5 sampling site), which means that this stable hydrated salt may exist even in the vast sunlight-exposed area of ​​the moon.This provides new possibilities for the future development and utilization of lunar resources.

(CCTV reporter Shuai Junquan and Chu Erjia)

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