Scientists have discovered a massive formation of radioactive granite below the surface of the far side of the Moon, and this unexpected rock formation may give researchers some clues about our Moon’s long history, according to new research.

In an article published this week in the journal NatureThe existence of subterranean granite suggests that the less-explored and always-facing far side of the moon was once home to one or more volcanoes that erupted early in the moon’s history, about 3.5 billion years ago.

“Any large granite body we found on Earth fed a large group of volcanoes,” co-author Matthew Ziegler, a professor at Southern Methodist University and a research fellow at the Planetary Sciences Institute, said in a statement.

Ziegler added that the underground deposits of erupted rock, called batholiths, left behind after volcanoes have cooled, are “much larger than the volcanoes they feed on at the surface.” “For example, the Sierra Nevada Mountains are a batholith leftover from a long-existing chain of volcanoes in the western United States.”

To determine the chemical composition of the radioactive Moon deposit, the researchers used microwave frequencies to measure the compound’s geothermal activity. From the data, they were able to conclude that the deposit contains certain radioactive elements that can only be attributed to granite.

Still, the results were somewhat surprising. Granite is rare on the Moon, although the region of the Moon where the mysterious rock was discovered – often referred to as the Compton-Belkovich Anomaly – contains a known volcanic complex.

However, the newly discovered piece of granite is quite large and exceeds 48 kilometers in diameter.

“The staggering size and geographic extent of this feature suggest the existence of an advanced Earth-like granite system,” the researchers write.

Despite exciting new discoveries, scientists may have more questions than answers.