What the researchers found deep in the lunar interior: a solid iron ball 300 miles across, wrapped in molten iron another 56 miles thick, topped with a 93-mile layer of partially molten material.

The lunar soil (regolith) contains iron, aluminum, calcium, silicon, titanium, and oxygen, as well as trace amounts of lighter elements such as carbon, sulfur, and nitrogen.

But scientists working on a way to harvest oxygen from the iron oxide in lunar soil for future moon bases realized that they happened on a better way to make steel here on Earth.