A recent scientific breakthrough has revealed that around 4 billion years ago, the Moon was abundant in water. This discovery, led by postdoctoral researcher Tara Hayden at the University of Western Ontario, opens a new window into the Moon's evolution and could influence future lunar missions.
The study focused on a lunar meteorite, a fragment from the Moon's surface, where Hayden found apatite, a common mineral. This finding allows for unprecedented analysis of a poorly understood era of the Moon when it was still partly molten. The results suggest that the lunar crust of that time contained more water than previously thought by scientists.
Lunar samples brought back by the Apollo missions in the 1960s and 1970s initially led to the belief that the Moon was extremely water-deficient. However, the 2008 discovery of significant water amounts in the Apollo sample collection challenged this view. Since then, lunar meteorites that landed on Earth have continued to reveal a Moon that is far from dry.
Hayden points out that the Apollo samples were taken from only 5% of the lunar surface. Therefore, lunar meteorites provide a unique opportunity to study unexplored regions of the Moon. By focusing on the apatite found in ferroan anorthosites—lunar rocks formed directly from the Lunar Magma Ocean—Hayden was able to directly investigate this phase in lunar evolution.
These findings come at a pivotal moment for lunar science as humanity prepares to return to the Moon with the Artemis mission. Frozen water on the lunar surface could play a vital role in supporting astronauts and producing hydrogen as fuel for return trips to Earth or travels to other destinations in the solar system.
This research on lunar rocks is detailed in an article published in
Nature Astronomy. It opens up new perspectives on the presence of water on the Moon, challenging established assumptions and suggesting that the lunar surface may harbor more water than previously thought.
Apatite, a Key Mineral to Understanding the History of Water on the Moon
Apatite is a mineral that plays a crucial role in understanding the Moon's water history. It is a group of calcium phosphate with the chemical formula Ca₅(PO₄)₃(F,Cl,OH), and can include fluorine, chlorine, and hydroxyl. This mineral is commonly found in terrestrial rocks, meteorites, and, as recent discoveries show, also in lunar rocks.
What makes apatite particularly interesting to scientists is its ability to incorporate volatiles—elements or compounds that can evaporate or decompose at relatively low temperatures—into its structure. In the lunar context, the most relevant volatiles are water (H₂O) and hydroxylated compounds (OH). Apatite thus serves as an indicator of the presence of water and other volatiles in the lunar rocks.
By examining the composition and structure of the apatite found in lunar meteorites, researchers can infer the amount and form of water that was present in the early lunar crust. This offers valuable clues about the Moon's geological history and, by extension, the evolution of planetary environments in our solar system.
The discovery of apatite in lunar meteorites, particularly in ferroan anorthosites—rocks formed directly from the Lunar Magma Ocean—is significant. It suggests that water was present even during phases when the Moon was predominantly molten, thus revolutionizing our understanding of the Moon's hydrological history. This discovery could have important implications for future lunar mission planning, especially for utilizing in-situ water resources.