The mysterious "man in the moon" face we see in the night sky - which is actually just a giant basin known as the Procellarum region - was not born from an asteroid strike as previously thought, but from a large plume of magma deep within the Moon's interior, new NASA data describes.
Made of volcanic terrain some 1,800 miles in diameter, the circular Procellarum region is nearly as wide as the United States. Scientists have long supposed that this basin was formed from a massive impact, followed by subsequent asteroid collisions. However, new data obtained by NASA's GRAIL mission indicates that its border is not circular, but polygonal, composed of sharp angles that could not have been created by a massive asteroid.
Instead, MIT researchers suggest that this angular outline is the result of giant tension cracks that formed in the Moon's crust as it cooled around an upwelling plume of hot magma from the deep interior.
"A lot of things in science are really complicated, but I've always loved to answer simple questions," Maria Zuber, lead investigator for the GRAIL (Gravity Recovery and Interior Laboratory) mission, said in a statement.
"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!"
As described in the journal Nature, as the cracks occurred, they formed a sort of "plumbing system" through which magma could travel from deep within the Moon to its surface. Eventually, this molten lava filled the region's smaller basins, creating what we see today as dark spots on the near side of the Moon - features that lent the name "man in the moon."
Although the mystery has been solved, researchers still don't know exactly what caused these magma plumes in the first place.
"It could be due to radioactive decay of heat-producing elements in the deep interior," Zuber speculated. "Or, conceivably, a very early large impact triggered the plume."
I guess that's one more mystery that will remain unsolved... for now.