Stunning new research shows that we may have been totally wrong about how the moon formed 4.5 billion years ago.

Scientists believe that an object the size of Mars smashed into a young Earth eons ago, creating a huge amount of debris that eventually turned into the moon — but what new research shows is that it was a colossal head-on collision, according to a Discovery News report.

To arrive at their conclusions, researchers examined seven moon rocks that were collected on three of the Apollo missions, as well as one sample from a lunar meteorite that struck Earth and compared it to rocks found in the Earth’s mantle. They found that there were nearly identical oxygen isotopes on both the Earth and the moon, indicating that Earth’s collision to the body, called Theia, was quite a spectacular and thorough collision.

Previously, scientists had thought the bodies hadn’t mixed as much, indicating that it wasn’t a direct strike, but this new research suggests differently. If it had been just a glancing blow, Theia would have a different oxygen makeup than Earth, but this research indicates that the two bodies mixed very thoroughly.

“We don’t see any difference between the Earth’s and the moon’s oxygen isotopes; they’re indistinguishable,” Edward Young, lead author of the new study and a UCLA professor of geochemistry and cosmochemistry, said in a statement. “Theia was thoroughly mixed into both the Earth and the moon, and evenly dispersed between them. This explains why we don’t see a different signature of Theia in the moon versus the Earth.”