What Created the 'Man in the Moon': Massive Magma Plume Rose from Beneath the Surface

Most of us are familiar with the "man in the moon," the shadowy face that appears in the night sky. Now, scientists have examined new data from NASA's GRAIL mission and have found that the giant basin probably wasn't created by a massive asteroid strike, but rather was formed from a large plume of magma deep within the moon's interior.

The basin that's commonly referred to as the "man in the moon" is called the Procellarum region. It's a roughly circular piece of volcanic terrain that's about 1,800 miles in diameter. Previously, scientists believed that this area was formed by a massive impact, which would make it the largest impact basin on the moon. Subsequent impacts overprinted the area with smaller basins.

Yet it looks like that this may not be the whole story. The scientists have found that the border of the Procellarum region isn't circular, but polygonal. It consists of sharp angles that couldn't have been created by a massive asteroid. Instead, it's more likely that it was created from an upwelling plume of hot material.

"A lot of things in science are really complicated, but I've always loved to answer simple questions," said Maria Zuber, principal investigator for the GRAIL, in a news release. "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 researchers mapped the Procellarum region using data obtained by GRAIL. They determined the strength of gravity across the moon's surface in order to create a highly detailed map, which they used to determine where the crust thickens and thins. In the end, they were able to get a better view of the Procellarum region than ever before.

"How such a plume arose remains a mystery," said Zuber. "It could be due to radioactive decay of heat-producing elements in the deep interior. Or, conceivably, a very early large impact triggered the plume. But in the latter case, all evidence for such an impact has been completely erased. People who thought that all this volcanism was related to a gigantic impact need to go back and think some more about that."

The findings are published in the journal Nature.