Using the Miniature Radio Frequency (Mini-RF) instrument on NASA’s Lunar Reconnaissance Orbiter spacecraft, mission members have found evidence that the Moon’s subsurface may be richer in minerals like iron and titanium than previously thought.

The Moon is widely believed to have originated from the collision of a Mars-sized proto-plant with the young Earth. In theory, the Moon’s bulk chemical composition should resemble that of the Earth. But many parts of the surface, such as the lunar highlands, appear to be metal-poor.

The mini-RF, explains NASA, allowed scientists to measure an electrical property known as the dielectric constant within lunar soil piled on crater floors in the Moon’s northern hemisphere.

The research team noticed that the property increased with crater size — up to a certain point. When the craters reached three to twelve miles in diameter, the property remained constant. No one expected to find the relationship. Says the NASA article:

Discovery of this pattern opened a door to a new possibility. Because meteors that form larger craters also dig deeper into the Moon’s subsurface, the team reasoned that the increasing dielectric constant of the dust in larger craters could be the result of meteors excavating iron and titanium oxides that lie below the surface. Dielectric properties are directly linked to the concentration of these metal minerals.

If their hypothesis were true, it would mean only the first few hundred meters of the Moon’s surface is scant in iron and titanium oxides, but below the surface, there’s a steady increase to a rich and unexpected bonanza. …

The larger craters, with their increased dielectric material, were also richer in metals, suggesting that more iron and titanium oxides had been excavated from the depths of 0.3 to 1 mile (0.5 to 2 kilometers) than from the upper 0.1 to 0.3 miles (0.2 to 0.5 kilometers) of the lunar subsurface.