The Moon May Be More Metallic Than Previously Thought

Researchers have uncovered evidence to suggest that the moon may be more metallic than previously thought.

According to a study published in the journal Earth and Planetary Science Letters, the subsurface of our only natural satellite might be richer in metals such as iron and titanium—a finding that could help to shed light on the moon's formation.

Scientists think that the moon was born following the gravitational collapse of a debris cloud produced by the collision of a Mars-sized protoplanet and the young Earth. This can explain why the total chemical composition of the two bodies is similar.

However, when you look in detail at the moon's surface, rocks in the lunar highlands—which make up more than 80 percent of the surface—contain less metal-bearing minerals than many found on Earth. Meanwhile rocks found in the satellite's large, darker plains—known as "marias"—contain higher quantities.

Experts have long puzzled over this discrepancy, and various hypotheses have been proposed to try and explain how the impact of the Mars-sized protoplanet could have contributed to the observed differences in chemical composition.

Now, a group of scientists operating the Miniature Radio Frequency (Mini-RF) instrument on NASA's Lunar Reconnaissance Orbiter (LRO) spacecraft have conducted a study that provides new insights into this puzzle.

The scientists used the Mini-RF to investigate lunar soil in crater floors in the moon's northern hemisphere, while comparing these results with data collected by the LRO's Wide-Angle Camera, Japan's Kaguya mission and NASA's Lunar Prospector spacecraft.

They found that larger craters—those measuring 3 to 12 miles wide—were richer in metals than smaller craters. The team say this finding can be explained by the fact that large meteor strikes—which produced the larger craters—dug up iron and titanium oxides from below the surface.

This suggests that the only the first few hundred feet of the moon's surface is lacking in these substances, whereas they are found in higher quantities deeper down.

The moon
The moon seen from Amsterdam, the Netherlands, on April 7, 2020. Soccrates Images/Getty Images

"The LRO mission and its radar instrument continue to surprise us with new insights about the origins and complexity of our nearest neighbor," Wes Patterson, Mini-RF principal investigator from the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, and co-author of the study, said in a statement.

The latest results shed new light on the distribution of metals in the lunar subsurface, thus providing new evidence that can help scientists better understand the evolutionary history of the moon.

"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, LRO project scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, said in a statement.