The Earth and the Moon are similar in chemistry and composition, and a new study may suggest why.
Researchers at Harvard University theorize that the Moon was once part of the Earth -- and it could have spun off during a massive collision with another giant body in space.
During that time, the Earth would have been spinning much faster, and a day would have lasted between two and three hours.
The accelerated rate of rotation would have been able to launch enough material to create a moon, the study says.
The findings have been published in a recent issue of the journal Science.
With files from Reuters