Chinese researchers have proposed that surplus argon-40 detected in lunar soil may originate from a stream of particles escaping Earth's atmosphere, a process they describe as Earth wind. The work, led by the Northwest Institute of Eco-environment and Resources (NIEER) under the Chinese Academy of Sciences, was published in the planetary science journal Icarus.
Argon, a noble gas found in by Riko Seibo
Tokyo, Japan (SPX) Sep 30, 2025
Chinese researchers have proposed that surplus argon-40 detected in lunar soil may originate from a stream of particles escaping Earth's atmosphere, a process they describe as Earth wind. The work, led by the Northwest Institute of Eco-environment and Resources (NIEER) under the Chinese Academy of Sciences, was published in the planetary science journal Icarus.
Argon, a noble gas found in Moon soil, preserves chemical records vital for understanding the Moon's interior, surface evolution, and Earth-Moon material exchange. Li Liwu, a NIEER researcher, explained that isotopic analysis of lunar argon offers new clues to key questions about planetary processes. He added that unexplained surpluses of argon-40 have remained a major topic in planetary science.
The study analyzed argon isotopes in samples returned by China's Chang'e 5 mission. Researchers used stepwise heating and degassing techniques to separate noble gas isotopes, then examined the isotopic compositions. Their findings revealed two distinct sources of argon-40: one derived from radioactive decay of potassium-40 within the soil itself, and another linked to argon-36, suggesting an external origin.
The team concluded that this latter argon-40 is likely carried by Earth wind, produced by atmospheric particles escaping Earth and transported along the planet's magnetosphere to the lunar surface. This mechanism provides a possible explanation for long-standing questions over lunar argon surpluses.
According to Li, the findings not only refine understanding of volatile exchanges between Earth and the Moon but also contribute to broader knowledge of how planetary atmospheres can influence nearby celestial bodies. He noted that future analysis of samples from Chang'e 6 and other lunar missions could further test the extent of Earth wind's reach.
The Chang'e 5 spacecraft returned 1,731 grams of lunar soil and rock to Earth in December 2020, enabling detailed laboratory studies that continue to reshape scientific perspectives on the Moon's evolution and its connection to Earth.
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