Discovery changes understanding of water¡¯s history on the Moon
Western cosmochemist finds early lunar crust had more water than previously estimated
New research from a Western University postdoctoral fellow shows the early lunar crust, which makes up the surface of the Moon, was considerably enriched in water more than 4 billion years ago, counter to previously held understanding. The discovery is outlined in a study published today in the high impact journal Nature Astronomy.
Working with a meteorite she classified as one that came from the Moon while a graduate student at The Open University (U.K.), Tara Hayden identified, for the first time, the mineral apatite (the most common phosphate) in a sample of early lunar crust.
The research offers exciting new evidence that the Moon¡¯s early crust contained more water than was originally thought, opening new doors into the study of lunar history.
¡°The discovery of apatite in the Moon¡¯s early crust for the first time is incredibly exciting - as we can finally start to piece together this unknown stage of lunar history. We find the Moon¡¯s early crust was richer in water than we expected, and its volatile stable isotopes reveal an even more complex history than we knew before,¡± said Hayden, currently working as a cosmochemist with renowned planetary geologist Gordon ¡°Oz¡± Osinski in Western¡¯s department of Earth sciences.
¡°Lunar meteorites are revealing new, exciting parts of the Moon¡¯s evolution and expanding our knowledge beyond the samples collected during the Apollo missions. As the new stage of lunar exploration begins, I am eager to see what we will learn from the lunar far side,¡± said Hayden.
The Apollo samples were first assumed to be ¡®volatile-poor¡¯ upon their return from the Moon, leading to the wide-known description of the Moon as ¡®bone dry.¡¯
In 2008, Alberto Saal and other researchers discovered the presence of significant amounts of water and other volatiles in glass beads from the Apollo sample collection. This set forth fifteen years of re-analysis of the Apollo samples while newly found lunar meteorites have revealed the Moon had much more water across its surface.
¡°We know most about the history of water on the Moon from the Apollo samples, but those samples are thought to only represent about five per cent of the entire Moon surface,¡± said Hayden. ¡°Until we get more samples back in the upcoming Artemis missions, the only other samples from the surface we have are meteorites.¡±
Hayden made the discovery at The Open University during her PhD studies while verifying a rock sample for a collector as a lunar meteorite. Beyond its identification, the sample proved to be holding a key piece of data about water on the Moon.
¡°I was so lucky the meteorite not only came from the Moon but remarkably, featured chemistry so vital to our understanding about lunar water-bearing minerals,¡± said Hayden.
This work was focused primarily on the mineral apatite, which contains volatile elements in its mineral structure. Apatite was found in all lunar rock types except glass beads and ferroan anorthosites, the latter representing the Moon¡¯s early crust.