This image based on data from NASA’s Lunar Reconnaissance Orbiter spacecraft shows the face of the Moon that we see from Earth. The more we learn about our closest neighbor, the more we begin to understand the Moon as a dynamic place with useful resources that could one day even support the human presence. Credit: NASA / GSFC / Arizona State University
Radar spots indicate that the Moon is more metallic than previously thought
What started as a lurking ice hunt in polar lunar craters turned into an unexpected find that might help clear up a bit of a murky history of the Moon’s formation.
Team members of the Miniature Radio Frequency (Mini-RF) instrument at POTThe Lunar Reconnaissance Orbiter (LRO) spacecraft found new evidence that the Moon’s subsoil may be richer in metals, such as iron and titanium, than researchers thought. That finding, published July 1 in Earth and Planetary Science Letters, could help establish a clearer connection between Earth and the Moon.
“The LRO mission and its radar instrument continue to surprise us with new insights into the origins and complexity of our closest neighbor,” said Wes Patterson, Mini-RF principal investigator at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, and a co-author of the study.
Substantial evidence points to the Moon as the product of a collision between a Marslarge and young earth, formed from the gravitational collapse of the remaining debris cloud. Consequently, the Moon’s bulk chemical composition closely resembles that of Earth.
However, look in detail at the Moon’s chemical composition, and that story becomes murky. For example, on the bright plains on the Moon’s surface, called the lunar highlands, rocks contain smaller amounts of metal-containing minerals relative to Earth. That finding could be explained if Earth had fully differentiated into a core, mantle, and crust before impact, leaving the Moon largely metal-poor. But turn to the Moon Maria, the darker great plains, and the abundance of metals becomes richer than that of many rocks on Earth.
This discrepancy has baffled scientists, leading to numerous questions and hypotheses about how much the impactful protoplanet may have contributed to the differences. The Mini-RF team found a curious pattern that could lead to a response.
Using Mini-RF, the researchers sought to measure an electrical property within the lunar soil stacked in the craters of the Moon’s northern hemisphere. This electrical property is known as the dielectric constant, a number that compares the relative abilities of a material and the vacuum of space to transmit electrical fields, and could help locate ice lurking in the shadows of the crater. However, the team noted that this property increased with the size of the crater.
For craters approximately 1 to 3 miles (2 to 5 kilometers) wide, the material’s dielectric constant steadily increased as craters grew larger, but for craters 3 to 12 miles (5 to 20 kilometers) wide, the property remained constant.
“It was an amazing relationship that we had no reason to believe would exist,” said Essam Heggy, co-investigator of the Mini-RF experiments at the University of Southern California, Los Angeles and lead author of the published article.
The discovery of this pattern opened a door to a new possibility. Because meteors that form larger craters also dig deeper into the Moon’s subsoil, the team reasoned that the increasing dielectric constant of dust in larger craters could be the result of meteorites digging iron and titanium oxides. that are below the surface. The dielectric properties are directly related to the concentration of these metallic minerals.
If your hypothesis were true, it would mean that only the first few hundred meters of the Moon’s surface are scarce in iron and titanium oxides, but below the surface, there is a steady increase in a rich and unexpected boom.
Comparing Mini-RF crater floor radar images with metal oxide maps from the LRO wide-angle camera, Japan’s Kaguya mission, and NASA’s Lunar Prospector spacecraft, the team found exactly what they had suspected. The larger craters, with their higher dielectric material, were also richer in metals, suggesting that more iron and titanium oxides have been excavated from depths of 0.3 to 1 mile (0.5 to 2 kilometers) than from the higher 0.1 0.3 miles (0.2 to 0.5 kilometers) from the lunar subsoil.
“This exciting Mini-RF result shows that even after 11 years of operation on the Moon, we are still making new discoveries about the ancient history of our closest neighbor,” said Noah Petro, LRO project scientist at the Flight Center. NASA’s Goddard Space Station. in Greenbelt, Maryland. “MINI-RF data is incredibly valuable in telling us about the properties of the lunar surface, but we use that data to infer what was happening more than 4.5 billion years ago!”
These results follow recent evidence from NASA’s Gravity Recovery and Interior Laboratory (GRAIL) mission suggesting that there is a significant mass of dense material a few tens to hundreds of kilometers below the huge South Pole-Aitken basin of the Moon. , indicating that dense materials are not evenly distributed in the Moon’s subsoil.
The team emphasizes that the new study cannot directly answer the remaining questions about the formation of the Moon, but it reduces the uncertainty in the distribution of iron and titanium oxides in the lunar subsoil and provides critical evidence necessary to better understand the formation of the Moon and its connection to earth.
“It really raises the question of what this means for our earlier training hypotheses,” Heggy said.
Eager to discover more, researchers have already begun examining crater floors in the Moon’s southern hemisphere to see if the same trends exist there.
LRO is managed by NASA’s Goddard Space Flight Center in Greenbelt, Maryland, for the Science Mission Directorate at NASA headquarters in Washington. Mini-RF was designed, built, and tested by a team led by APL, Naval Air Warfare Center, Sandia National Laboratories, Raytheon, and Northrop Grumman.
