The giant moon basin often referred to as the Man in the Moon was long thought to have been created by the impact of an asteroid, but scientists now believe the dark splotch was formed by a magma plume that swelled to the surface.
According to MIT News, researchers at the school compiled a high resolution map of the basin — known in science speak as the Procellarum — using data from NASA's 2012 GRAIL mission (Gravity Recovery and Interior Laboratory) to make their discovery.
"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," said Maria Zuber, geophysics professor and MIT's vice president for research.
The GRAIL mission collected gravitational data from January to December 2012 using twin probes that orbited the moon. By measuring the variable distance between the probes as they circled the moon, researchers were able to create a high-resolution map of where the lunar crust thickens and thins.
This detailed topographical map revealed that the edges of the Procellarum contain 120-degree angles — a shape asteroids are not likely to produce when they impact a celestial body like the moon. Instead, the scientists now believe that as the moon was formed and cooled, a magma plume underneath the basin created fractures that bled forth rivers of molten lava.
"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."
According to The Washington Post, the basin, which appears darker in color than most of the moon, forms the cheek of the man in the moon, and the hindquarters of the "moon rabbit" in Chinese mythology.