Water has been discovered inside tiny glass beads scattered across the moon, according to scientists who analysed lunar soil samples retrieved during China’s Chang’e-5 mission in 2020. The discovery suggests a potential reservoir of water for future human activities on the lunar surface. The moon was previously believed to be dry, but several missions over the last few decades have shown that there is water both on the surface and trapped inside minerals. The glass beads, which are formed when rocks melt and cool during high-energy flash-heating events caused by impactors such as micrometeoroids and large meteoroids, contain water molecules formed by the action of the solar wind on the moon’s surface. The solar wind is a stream of charged particles, primarily protons and electrons, emanating outward from the corona, the outermost part of the sun’s atmosphere, and permeating the solar system. Solar wind-derived water is produced by the reaction of solar hydrogen with oxygen present at the surface of the lunar glass beads. These spheres then act like a sponge for the water.
For future moon exploration, including potential long-term lunar bases staffed with astronauts, water is of vital importance not only as a drinking supply but as a fuel ingredient. While the moon lacks bodies of liquid water that are a hallmark of Earth, its surface is thought to harbour a fairly substantial amount of water, for example in ice patches residing in permanently shadowed locales and trapped in minerals. Researchers see promise in obtaining water from the glass beads, perhaps through a heating process to release vapour that would then turn into liquid through condensation. The glass beads were found to hold a water content of up to about 2,000 parts per million by weight. Such impact glass beads are believed to be a common part of lunar soils, found globally and spread evenly.
“Water is the most sought-after commodity for enabling sustainable exploration of planetary surfaces,” said planetary scientist Sen Hu of the Chinese Academy of Sciences’ Institute of Geology and Geophysics, a co-author of the study published in the journal Nature Geoscience. “Knowing how water is produced, stored and replenished near the lunar surface would be very useful for future explorers to extract and utilise it for exploration purposes.” The capsule returning the soil samples to Earth landed in the northern Chinese region of Inner Mongolia. About 3.8 pounds (1.7 kg) of soil were collected in the Chang’e-5 mission, with 32 glass beads – tens to hundreds of micrometres wide – examined in the study from the small amount of soil made available for this research. Hu said he believes that such impact glass beads are a common part of lunar soils, found globally and spread evenly.