A higher concentration of metal in Moon’s craters provides new insights into its origin.

Life on Earth would not be possible without the Moon; It keeps the axis of rotation of our planet stable, which controls the seasons and regulates our climate. However, there has been considerable debate about how the Moon formed. The popular hypothesis holds that the Moon was made up of a body the size of Mars that collided with Earth’s upper crust, which is metal poor. But new research suggests that the Moon’s subsoil is richer in metals than previously thought, providing new insights that could challenge our understanding of that process.

Today, a study published in Letters of Earth and Planetary Science sheds new light on the composition of the dust at the bottom of the Moon’s craters. Led by Essam Heggy, research scientist in electrical and computer engineering at USC’s Viterbi School of Engineering, and co-investigator of the Mini-RF instrument aboard NASA’s Lunar Reconnaissance Orbiter (LRO), members of the The Lunar Reconnaissance Orbiter (LRO) Miniature Radio Frequency (Mini-RF instrument) used radar to image and characterize this fine dust. The researchers concluded that the Moon’s subsoil may be richer in metals (i.e. Fe and Ti oxides) than scientists believed.

According to the researchers, the fine dust at the bottom of the Moon’s craters is actually material forced out from under the Moon’s surface during meteorite impacts. By comparing the bottom metal content of the largest and deepest craters with that of the smallest and shallowest craters, the team found higher concentrations of metal in the deepest craters.

What does a change in the presence of registered underground metal have to do with our understanding of the Moon? The traditional hypothesis is that about 4.5 billion years ago there was a collision between Earth and a proto-planet the size of Mars (called Theia). Most scientists believe that the collision fired a large chunk of Earth’s metal-poor upper crust into orbit, eventually forming the Moon.

A puzzling aspect of this theory of Moon formation has been that the Moon has a higher concentration of iron oxides than Earth, a fact well known to scientists. This particular research contributes to the field in that it provides information about a section of the moon that has not been studied frequently and postulates that an even higher concentration of metal may exist deeper below the surface. It’s possible, the researchers say, that the discrepancy between the amount of iron in the Earth’s crust and the Moon could be even greater than scientists thought, questioning the current understanding of how the Moon formed.

The fact that our Moon may be richer in metals than Earth challenges the notion that parts of Earth’s mantle and crust were launched into orbit. A higher concentration of metal deposits may mean that other hypotheses about the formation of the Moon must be explored. It may be that the collision with Theia has been more devastating to our early Earth, with much deeper sections launched into orbit, or that the collision could have occurred when Earth was still young and covered in an ocean of magma. Alternatively, more metal could hint at complicated cooling of an early molten lunar surface, as suggested by several scientists.

According to Heggy, “By improving our understanding of how much metal the Moon’s subsoil actually has, scientists can limit ambiguities about how it has formed, how it is evolving, and how it is helping to maintain livability on Earth.” He further added: “Our solar system only has more than 200 moons; understanding the crucial role these moons play in the formation and evolution of the orbiting planets can give us a deeper insight into how and where life conditions outside of the Earth and what could happen, it seems. “

Wes Patterson of the Planetary Exploration Group (SRE), Space Exploration Sector (SES) at the Johns Hopkins University Applied Physics Laboratory, who is the project’s principal investigator for Mini-RF and co-author of the study, added: ” The LRO mission and its Mini-RF radar imager continue to surprise us with new insights into the origins and complexity of our closest neighbor. “

The team plans to continue making additional radar observations of more crater floors with the Mini-RF experiment to verify initial findings from the published research.