"These new data suggest the top 130 feet of the lunar surface are made up of multiple layers of dust, soil, and broken rocks, Feng said. Hidden within these materials was a crater, formed when a large object slammed into the moon. Feng and his colleagues hypothesized that the rubble surrounding this formation was ejecta — debris from the impact. Farther down, the scientists discovered five distinct layers of lunar lava that seeped across the landscape billions of years ago."

Just in case anyone thought it was actually going to be some type of structure like caverns or something like I did.