The impact of meteorites on our satellite resulted in the formation of glass “balls”, which, under the effect of the solar wind, are able to store up to 2.7 × 1014 kg of water in the entire ground lunar. So say Chinese scientists after analyzing samples collected by their Chang’e 5 spacecraft.
While the Moon was previously thought to be dry, samples collected by Apollo missions in the 1970s already revealed the existence of water trapped in minerals inside the Moon. Orbiters have also detected it all over the lunar surface, especially at the poles.
The scientists considered that the interaction of the solar wind with the materials of the ground of our satellite could produce water and maintain a cycle of this element there. However, no aqueous reservoir had been identified on the lunar surface. Now an international team led by China thinks they have found it, as published in the magazine natural geosciences.
These are the “impact glass balls” (IGB), formed by the cooling of the molten material ejected after the constant bombardment of asteroids which, in the form of meteorites, fall on the Moon. This granular material is dispersed over its entire surface and can store significant amounts of water under the effect of solar winds.
Analysis of lunar soil samples
Researcher Huicun He from the Chinese Academy of Sciences, together with other colleagues from his country and the United Kingdom, analyzed the water content of these IGBs using lunar soil samples collected by the space probe Chang’ e 5. This probe landed on the moon in December 2020 and that same month it brought the collected material to Earth for analysis.
After measuring the abundance, the isotopic composition of hydrogen and the variations between the core and the edge of the water of the IGBs extracted from the lunar soil, the results reveal that the water they store is compatible with an origin solar wind. For example, the characteristic signature of a positively charged isotope of hydrogen (H+) appears.
Glass “balls” accumulate water by diffusion
In addition, the distribution of water in the individual glass “beads” indicates that H20 can accumulate there rapidly by diffusion, over timescales of only a few years, and be rapidly released. The authors suggest that this presents an efficient recharge mechanism for driving an active water cycle on the Moon’s surface.
“IGBs preserve hydration signatures and show an abundance of water consistent with inward diffusion of water from the solar wind“, point out Huicun He and his colleagues. “Diffusion modeling estimates diffusion times to be less than 15 years at a temperature of 360 K (86.85 °C). These short diffusion times suggest an efficient water recharge mechanism that could support the water cycle on the lunar surface.”.
The researchers note in their study:We estimate that the amount of water stored in these impact glass balls in lunar soils can reach 2.7 × 1014 kg. Our direct measurements of this lunar surface water reservoir show that IGBs can store significant amounts of water from the solar wind on the Moon.“.
The authors note that the water trapped in these impact glass “beads” could represent a potential water resource for future lunar exploration, as it is relatively easy to extract, they say. They also conclude that this type of vitreous material can harbor similar water deposits in other airless bodies.
Hejiu Hui et al. “A Solar Wind-Derived Water Reservoir on the Moon Hosted by Impact Glass Beads”. Nature Geoscience, 2023.