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CUHK joint study reveals Moon volcanoes continue to exhale for years after erupting
Discovery offers new pathways to explore lunar evolution
With lunar exploration once again in the global spotlight following recent missions to the far side of the Moon, a collaborative study by The Chinese University of Hong Kong (CUHK) and the University of California, Los Angeles (UCLA) has proposed a novel explanation for the formation of lunar volcanic glass[1]. The research reveals that the environmental impact of lunar volcanic eruptions can last for years, updating the scientific consensus.
Previously, most scientists thought that lunar volcanic glass formed from the rapid cooling and degassing of magma during volcanic eruptions. However, after analysing the famous sample 74220[2], orange volcanic glass beads brought back to Earth by Apollo 17 in 1972, the research team discovered that lunar ejecta did not lose all its gas components at once while in flight. Instead, when these materials fell back to the lunar surface and were buried by surrounding debris, they continued to slowly cool and exhale gases for several years. This study will help scientists reassess the long-term impact of lunar volcanic activity on the Moon’s environment, and provide a new approach for studying the Moon’s internal water resources and other volatile substances, such as sulphur, chlorine and fluorine. The findings were recently published in the prestigious international scientific journal Nature Communications.
Breaking the traditional understanding of brief degassing
Volcanic glass beads are crucial to the study of the Moon’s composition. Scientists generally believe these tiny beads originated deep within the Moon and act as time capsules that preserve vital information about the Moon’s internal moisture and other volatile substances. However, because these beads lose some water and volatiles during eruption and cooling, accurately estimating the original water content and elemental composition of the lunar interior requires an understanding of exactly when and how these substances were lost.
To solve this mystery, the research team conducted an in-depth analysis of volcanic glass beads from sample 74220 at various stages of cooling and degassing[3]. By combining computer models of diffusion, evaporation, and cooling, the team reconstructed the entire process from the eruption of the ejecta from beneath the lunar surface to its complete cooling.
The results showed that the traditional scientific assumption – that the glass beads only degas during their minutes-long flight – cannot explain the extremely low volatile content found in the Apollo 17 sample. The team proposed a groundbreaking perspective: after falling back to the lunar surface, the glass beads were likely buried by other volcanic deposits. Acting like an incubator, these deposits prevented the beads from cooling rapidly, causing them to slowly and continuously release volatiles over the following years.
Driving future lunar exploration
According to current scientific understanding, water exists on the Moon primarily as ice, concentrated in permanently shadowed regions at the lunar poles. According to the research team, this study could also reshape the scientific community’s understanding of lunar water resources. They note that if lunar ejecta can release gases for extended periods after falling back to the surface, this continuous emission could play a crucial role in maintaining a temporary, localised lunar atmosphere. This would significantly impact the Moon’s volatile cycle and could even help explain how lunar water ice is formed.
Professor Zhan Yan, co-first author of the study, from CUHK’s Department of Earth and Environmental Sciences, said: “The research shows that a lunar volcanic eruption can be not just a single, brief event; its subsequent impacts can last for years. This not only affects how we interpret the information about the lunar interior recorded in the Apollo samples but may also change our understanding of how surface moisture and other volatile components migrate on the Moon.”
Professor Ni Peng from UCLA, also a co-first author of the study, added: “The Apollo 17 volcanic glass beads have always been vital samples for the study of the Moon’s internal composition. Our research shows that if we ignore the prolonged cooling and continuous degassing process this ejecta undergoes after falling back to the lunar surface, scientists might underestimate the amount and composition of volatiles originally contained within the Moon.”
The team conclude that this research will help scientists reassess the long-term impact of lunar volcanic activity on the surface environment, offering new pathways for future studies of lunar samples, the evolution of lunar water resources, the mechanisms of polar ice formation and the creation of transient atmospheres.
For the full research, please visit: https://www.nature.com/articles/s41467-026-69087-8
[1] Volcanic glass beads are solidified molten lava droplets from prehistoric fire-fountain eruptions on the Moon.
[2] Sample 74220 is an orange lunar soil sample and an extremely rare pyroclastic deposit, formed by a fountain-like volcanic eruption.
[3] Degassing is the process of removing dissolved or trapped gases, such as water vapor, nitrogen, or oxygen, from liquids, solids or metals.
Concept art depicting a lunar volcanic eruption
The evolutionary stages of lunar volcanic glass beads: first, volatile-rich magma rises from beneath the surface. Next, a volcanic eruption on the lunar surface forms orange volcanic glass droplets that undergo a brief free-fall in a vacuum. Finally, the droplets fall back and accumulate into a pyroclastic deposit layer, where they slowly cool on the lunar surface and continue to degas for years.
Professor Zhan Yan, Department of Earth and Environmental Sciences, CUHK.
Professor Ni Peng, UCLA.
