Moon has higher reserves of iron, titanium and other metals than Earth, raises questions on its formation
The Moon has been harboring a secret for a long time. Below its surface, NASA detected metals such as iron and titanium — in amounts that are higher than the Earth's reserves. The discovery is now challenging what scientists know about the lunar body's origins.
Scientists stumbled upon the metal reserves while looking for ice buried in the Moon's craters. In 2018, NASA confirmed the presence of water ice on the surface. Since then, researchers have been trying to learn more about it, hoping it could uncover the mysteries about the lunar body's past. To learn more, scientists used the Miniature Radio Frequency (Mini-RF) instrument aboard NASA’s Lunar Reconnaissance Orbiter (LRO), a satellite orbiting the Moon.
During this quest, the team detected high amounts of metals in the craters.“This exciting result from Mini-RF shows that even after 11 years in operation at the Moon, we are still making new discoveries about the ancient history of our nearest neighbor,” Noah Petro, the LRO project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said in a statement. "The MINI-RF data is incredibly valuable for telling us about the properties of the lunar surface, but we use that data to infer what was happening over 4.5 billion years ago!"
NASA speculates that meteors may have crashed into the Moon, digging deeper into the subsurface and excavating iron and titanium oxides from below the surface. If the theory holds, then the lunar body could be hiding metals deep within its surface.
"The LRO mission and its radar instrument continue to surprise us with new insights about the origins and complexity of our nearest neighbor," says Wes Patterson, Mini-RF principal investigator from the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, and a study coauthor.
These findings also cast doubts on a widely-held theory: the Moon formed when a Mars-sized protoplanet collided with a young Earth 4.5 billion years ago. "It really raises the question of what this means for our previous formation hypotheses," says Essam Heggy, research scientist of electrical and computer engineering at the USC Viterbi School of Engineering, and co-investigator of the Mini-RF instrument. The Moon seems to be richer in metals than Earth, making the collision idea weak. Meanwhile, scientists still have to test other hypotheses to explain the Moon's formation.
The discovery was possible thanks to the Mini-RF instrument. It measures the electrical property — or the dielectric constant — of lunar soils within craters on the northern hemisphere. Water ice has a certain value, but the researchers detected a higher dielectric constant in some of the moon's cavities, suggesting that metals are present. The suspicion was then backed by other analyses, which found iron and titanium.
The team is exploring the southern hemisphere for metals. Studying the metal distribution on the Moon’s subsurface could pave the way for understanding its origins, its evolution, and the role it plays in making Earth habitable. Heggy added: "Our Solar System alone has over 200 moons – understanding the crucial role these moons play in the formation and evolution of the planets they orbit can give us deeper insights into how and where life conditions outside Earth might form and what it might look like."