New research is revealing that the Moon may have had more water in its early history than scientists previously believed. A study published in the journal Nature Astronomy shows that the Moon’s primitive crust, which makes up its surface, was significantly enriched in water over 4 billion years ago. This finding goes against earlier theories about the Moon’s dryness.
The discovery was made by Tara Hayden, a planetary scientist now working at Western University in Canada. While a graduate student at the UK’s Open University, Hayden studied a meteorite that she determined came from the Moon.
Examining this primitive lunar rock sample, she identified the mineral apatite for the first time. Apatite is a common phosphate mineral that can contain volatile elements like hydrogen and chlorine within its crystal structure.
Finding apatite in the Moon’s primitive crust is hugely exciting because it allows scientists to learn more about the Moon’s early formation. Analysis showed the crust was richer in water than expected, with clues hidden in the stable isotopes of volatile elements. This opens up new possibilities about the lunar evolution story.
Previously, samples brought back by the Apollo missions in the 1960s and 70s were thought to be “volatile-poor,” leading to the Moon being described as “bone dry”. But in 2008, significant water and other volatiles were discovered within Apollo glass beads. Since then, over 15 years of reanalysis has occurred. Meteorites that have recently fallen to Earth have also revealed that more water existed on the lunar surface.
However, Apollo samples are believed to only represent about 5% of the Moon’s surface. Until more samples are collected by upcoming Artemis missions, meteorites provide the only insights into areas not visited by Apollo. Hayden’s crucial discovery was made while verifying a meteorite sample for a collector during her Ph.D. studies.
Hayden’s work focused on the importance of apatite, which contains volatile elements within its mineral structure. Previously, apatite had been found in all lunar rock types except one—the ferroan anorthositic suite.
This represents the Moon’s primitive crust and is incredibly ancient, dating to 4.5-4.3 billion years ago. It formed directly from the Moon’s initial magma ocean. Finding apatite here allows scientists to study this early period for the first time.
Unraveling the water history of the Moon’s crust from around 4.5 billion years ago is key to understanding where water in our solar system originated. Ancient lunar rocks delivered via meteorites provide an excellent chance to conduct such research.
Hayden’s discovery comes at an opportune time, as NASA’s upcoming Artemis missions plan to return astronauts and samples from more parts of the lunar surface. Future investigations may reveal even more water resources available for use.
Hayden and other scientists are excited to apply these new insights to upcoming Artemis exploration objectives. Understanding the distribution and form of early lunar water could have major implications for long-term human presence on the Moon.
It has long been believed that the lunar surface has been desiccated for thousands or even millions of years, but there may be more water available than we thought on the surface of the Moon and we just have to find a way to extract it, Hayden said.
Sources
Western University | Hayden, T.S., Barrett, T.J., Anand, M. et al., Detection of apatite in ferroan anorthosite indicative of a volatile-rich early lunar crust. Nat Astron (2024). doi.org/10.1038/s41550-023-02185-5
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