Discovery changes understanding of the history of water on the Moon

New research led by a Western University postdoctoral researcher shows that the primitive lunar crust, which makes up the surface of the Moon, was significantly enriched in water more than 4 billion years ago, contrary to what is believed we previously believed. The discovery is described in a study published today (January 15) in the journal Natural astronomy.

Working with a meteorite she classified as coming from the moon while a graduate student at the Open University (UK), Tara Hayden identified, for the first time, the mineral apatite (the most common phosphate current) in a sample of the first lunar crust. .

The research offers exciting new evidence that the Moon’s early crust contained more water than initially thought, opening new doors to the study of lunar history.

“The discovery of apatite in the Moon’s early crust for the first time is incredibly exciting, because we can finally begin to piece together this unknown stage of lunar history. We find that the Moon’s early crust was richer in water than expected, and its volatile stable isotopes reveal an even more complex story than we previously knew,” said Hayden, who currently works as a cosmochemist with renowned planetary geologist Gordon “Oz” Osinski in the Department of Science. Western land.

“Lunar meteorites reveal exciting new parts of the Moon’s evolution and expand our knowledge beyond the samples collected during the Apollo missions. As the next stage of lunar exploration begins, I look forward to seeing what that we will learn from the dark side of the Moon.” Hayden said.

The Apollo samples were initially assumed to be “poor in volatile matter” upon their return from the Moon, leading to the well-known description of the Moon as being “dry to the bone.”

In 2008, Alberto Saal and other researchers discovered the presence of significant amounts of water and other volatile substances in glass beads from the Apollo sample collection. This required fifteen years of reanalyzing the Apollo samples, while newly discovered lunar meteorites revealed that the moon had much more water on its surface.

“We know more about the history of water on the Moon from the Apollo samples, but these samples are thought to represent only about five percent of the Moon’s total surface area,” Hayden said. “Until we collect more samples on future Artemis missions, the only other samples from the surface we have are meteorites.”

Hayden made the discovery at the Open University during his PhD. studies while checking a rock sample for a collector as a lunar meteorite. Beyond its identification, the sample turned out to contain key data about water on the Moon.

“I was so lucky that the meteorite not only came from the moon, but exhibited chemistry that was so vital to our understanding of lunar water-bearing minerals,” Hayden said.

This work has focused primarily on the mineral apatite, which contains volatile elements in its mineral structure. Apatite has been found in all types of lunar rocks except glass beads and ferroan anorthosites, the latter representing the early crust of the moon. The Ferroan Anorthosite Group is known to be incredibly old (4.5 to 4.3 billion years old) and is the only rock type known to have formed directly from the lunar magma ocean, when the moon was almost completely molten.

The discovery of apatite in this rock type made it possible for the first time to directly examine this unknown stage of lunar evolution.

“Unraveling the history of water in the first lunar crust formed about 4.5 billion years ago is important for improving our understanding of the origin of water in the solar system. Ancient rock samples coming from the moon in the form of lunar meteorites provide an excellent opportunity to have undertaken such investigations,” said Mahesh Anand, professor of planetary sciences and exploration at the Open University and Hayden’s official senior supervisor.

Future Artemis missions

Hayden says the timing of the discovery is perfect as NASA’s Artemis missions prepare for launch and researchers, including his current supervisor, develop programs and targets for astronauts.

“It has long been believed that the lunar surface has been dry for thousands or even millions of years, but perhaps there is more water available than we thought on the surface of the Moon and we simply need to find a way to extract it.” Hayden said.

Osinski is also excited about the potential opportunities of this new discovery.

Last year, Osinski was selected to be part of the NASA geology team developing the surface science plan for the first crewed lunar landing mission in more than 50 years. He will join his colleagues in the science backroom of Mission Control at NASA’s Johnson Space Center in Houston to provide support throughout the Artemis III mission.

“The findings from Tara are extremely exciting and will inform our sampling strategy for the Artemis III mission, where we hope to identify and sample some of the Moon’s earliest crusts,” Osinski said.