According to current models of planetary formation, Mercury has too much mass. A new explanation proposes that Mercury was created from a much larger parent planet that collided with a giant asteroid 4.5 billion years ago. Astronomers from the University of Bern ran various scenarios modeling early versions of Mercury. This scenario of an early cataclysm best matched the current mass and composition of Mercury. Some of the ejected material would have made it all the way to Venus and even to the Earth.
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