According to MIT researchers, newly obtained GRAIL data has revealed that the so-called “man in the moon” (or the Procellarum region) came from a volcanic plume, not an asteroid impact.

Researchers have developed a high-res map of the Procellarum and discovered that its border is not circular, but polygonal, made up of sharp angles that could not have been formed by a large asteroid. Alternatively, researchers think that the angular outline was created by enormous tension cracks in the moon’s crust as it cooled around a volcanic plume.

According to Maria Zuber, MIT’s vice president for research, as cracks developed, they created a “plumbing system” in the moon’s crust through which magma could travel to the lunar surface. The region’s smaller basins were filled by this magma, forming the dark spots observed on the moon.

“A lot of things in science are really complicated, but I’ve always loved to answer simple questions,” admits Zuber, principal investigator for the GRAIL mission. “How many people have looked up at the moon and wondered what produced the pattern we see — let me tell you, I’ve wanted to solve that one!”

The study’s findings are described in greater detail in the journal Nature.