New water reservoir found on the Moon’s surface

A team of researchers led by Professor HU Sen from the Chinese Academy of Sciences (CAS) has discovered that impact glass beads in Chang’e-5 (CE5) lunar soils contain water. The study, published in Nature Geoscience, suggests that these glass beads may represent a new water reservoir on the Moon that is responsible for the dynamic ingress and egress of solar wind-derived water, acting as a buffer for the lunar surface water cycle.

Although many lunar missions have confirmed the presence of structural water or water ice on the Moon, the exact amount and location of water on the lunar surface has been the subject of intense research. The lunar surface water has attracted much attention due to its potential for in-situ resource utilization by future lunar exploration missions and other space missions. 

The surface water on the Moon displays diurnal cycles and loss to space, indicating that there should be a hydrated layer or reservoir at depth in lunar soils to sustain the retention, release, and replenishment of water on the surface of the Moon.

Previous studies have been unable to explain the retention, release, and replenishment of water on the lunar surface, suggesting that there must be a yet-unidentified water reservoir in lunar soils that has the capacity to buffer the lunar surface water cycle. 

Under the guidance of Professor HU Sen, doctoral student HE Huicun proposed that impact glass beads, a ubiquitous component in lunar soils with an amorphous nature, were a potential candidate for investigation of the unidentified hydrated layer or reservoir in lunar soils.

To identify and characterize the missing water reservoir on the Moon’s surface, the researchers systematically characterized the petrography, major element composition, water abundance, and hydrogen isotope composition of the impact glass beads returned by the CE5 mission. 

The CE5 impact glass beads have homogeneous chemical compositions and smooth exposed surfaces, characterized by water abundance up to about 2,000 μg.g-1, with extreme deuterium-depleted characteristics. The negative correlation between water abundance and hydrogen isotope composition reflects the fact that water in the CE5 impact glass beads comes from solar winds.

The researchers also analyzed water abundance along six transects in five glass beads, which showed the hydration profiles of solar wind-derived water. Some glass beads were overlapped by a later degassing event. The impact glass beads acted as a sponge for buffering the lunar surface water cycle. The researchers estimate that the amount of water contributed by impact glass beads to lunar soils varies from 3.0 × 1011 kg to 2.7 × 1014 kg.

“These findings indicate that the impact glasses on the surface of the Moon and other airless bodies in the solar system are capable of storing solar wind-derived water and releasing it into space,” said Professor HU.

The discovery of a new water reservoir on the Moon provides important information for future lunar exploration missions and other space missions, as it may represent a valuable resource for sustained human presence on the Moon and beyond.

NASA’s plan for a sustained presence on the Moon is part of the Artemis program, which aims to land the first woman and the next man on the Moon by 2024. However, this timeline has recently been pushed back due to funding and technical challenges, and the new target date for the Artemis III lunar landing mission is 2025.

The Artemis program is not just about landing humans on the Moon, but also establishing a sustainable presence there. NASA’s long-term plan is to use the Moon as a testbed for technologies and systems that will be necessary for future crewed missions to Mars and other destinations.

To achieve this goal, NASA plans to build a Lunar Gateway, a small space station in orbit around the Moon, which will serve as a command center for human and robotic missions on the lunar surface. The agency is also developing a new lunar lander called the Human Landing System (HLS), which will transport astronauts from the Lunar Gateway to the surface of the Moon.

NASA aims to establish a sustainable presence on the Moon by 2028, which includes building a lunar base and conducting a range of scientific experiments and technology demonstrations. The agency also plans to work with international partners and commercial companies to achieve this goal.

This study was a collaboration with Nanjing University, The Open University, The Natural History Museum, The University of Manchester, and the University of Science and Technology of China. 

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