Beads of glass could become a key source of water for future crewed settlements on the moon, researchers say.
That claim is based on an assessment of the water contained within a sampling of glassy beads that were created over the course of millennia by cosmic impacts on the moon, and ended up being brought back to Earth in 2020 by China’s Chang’e-5 sample return mission.
A spectroscopic analysis determined that the beads contained more water than the researchers expected based on past studies. They surmised that interactions between hydrogen ions in the solar wind and oxygen-bearing materials in lunar soil created H2O molecules that could be trapped within the glass — and then diffused under the right conditions.
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Based on an extrapolation of such findings, the research team — headed by scientists from the Chinese Academy of Sciences — estimates that glass beads in lunar soil may contain up to 270 trillion kilograms (595 trillion pounds, or 71 trillion gallons) of water.
“We propose that impact glass beads in lunar soils are a prime water reservoir candidate able to drive the lunar surface water cycle,” the researchers report in Nature Geoscience.
Scientists have known for decades that the moon harbors reservoirs of water in the form of ice, concentrated at the poles. That sort of water is thought to have arrived in the form of cometary impacts, with water molecules migrating to permanently shadowed craters in the lunar polar regions.
Water was even detected in glass bead samples that were brought back to Earth by NASA’s Apollo lunar missions in the late 1960s and early 1970s — but the water detected in the Chang’e-5 samples was three times as abundant on average. And based on studies of basaltic glass beads on Earth, the researchers say it’s theoretically possible for the abundances to be even greater.
“This could be the result of dynamic diffusion and release of water in the impact glass beads controlled by the time-of-day temperature oscillations,” they write. “The dynamic ingress and egress of water in impact glass beads could have acted as a buffer to explain the global and daily variations of water abundance on the lunar surface and in the lunar exosphere.”
If enough of the beads could be collected, and if engineers can come up with an efficient way to heat up the beads and extract the H2O, that could give future lunar explorers a source of water for drinking, oxygen for breathing, and hydrogen for rocket fuel. Those are a couple of big “ifs,” but the research team says the problems seem solvable.
“These findings indicate that the lunar soils contain a much higher amount of solar wind-derived water than previously thought, which could be a water reservoir for in situ utilization in future lunar exploration,” they say in their study. “Indeed, this water entrapped in impact glass beads appears to be quite easy to extract.”
Astronauts could investigate the possibilities further as part of NASA’s Artemis program, which is due to send the first crewed mission since the Apollo era to the lunar surface in the mid-2020s. And if the newly reported findings hold up, they could also apply to the exploration of other worlds where water has been detected, such as Mercury and Vesta.
“Our findings indicate that the impact glasses on the surface of solar system airless bodies are capable of storing solar wind-derived water and releasing it to space,” the researchers behind the new study say.
Huicun He of the Chinese Academy of Science’s Key Laboratory of Earth and Planetary Physics is the lead author of the study in Nature Geoscience, titled “A Solar Wind-Derived Water Reservoir on the Moon Hosted by Impact Glass Beads.” Twenty-seven other researchers are listed as co-authors.