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In a surprising revision to earlier theories, researchers report that a massive feature on the moon formed due to lunar rifts.
Scientists had previously thought the Ocean of Storms, also known as Oceanus Procellarum, was created by a giant cosmic impact that left a crater about 2,000 miles wide (3,200 kilometers). But readings from NASA's GRAIL mission reveal that the feature is not round. Instead, it's surrounded by a strange giant rectangle beneath the surface.
This suggests the Ocean of Storms was not caused by a meteor strike, but formed as the moon's surface rifted apart.
"As a solid cools and contracts, fractures and faults can form, and these fractures will commonly take on a polygonal pattern," lead study author Jeffrey Andrews-Hanna of the Colorado School of Mines explained. On the moon, these ancient rift zones took on a rectangular shape.
"The observed pattern of gravity anomalies on the moon is so strikingly geometric and in such an unexpected shape that it is forcing us to think in new and different ways about the processes operating on the moon and planets in general," Andrews-Hanna said.
The research is detailed in Thursday's issue of the journal Nature.