The Moon likely formed when a giant body collided with Earth, chomping a hungry bite out of it in a spectacular collision billions of years ago. That’s the abridged bedtime story, at least. There are still many pages missing from the Moon’s biography.
For instance, scientists are unsure about the size and speed of the colliding object, the percentage of debris that fell to earth, flew into space or formed the moon and how long it took the debris to condense toward a single, compact body that now floats in space 240,000 miles from Earth.
Although scientists have an idea about the beginning and end of the story of the Moon's origin, the steps in between are less understood. For example, a disk of material likely formed out of the scattered debris and wrapped itself around the Earth shortly after the collision. The structure of this disk is not known, but scientists think that it says a lot about why the Moon is one eightieth the mass of the Earth and how long it took the Moon to for…