- More than 2 years ago
The story of how the moon was born may finally be complete. According to the most widely accepted scenario, a Mars-size rock slammed into the Earth 4.5 billion years ago, spewing material that coalesced into the moon. But where this gigantic impactor came from has remained unclear.
The moon’s chemical composition suggests that the impactor formed as close to the sun as Earth did, but another factor made that seem impossible: As Earth was forming, its gravity acted like a vacuum cleaner, gobbling up nearby debris.