How was the Moon formed? The most-widely-accepted theory suggests that billions of years ago, our young planet was struck by a body as large as Mars, forming the Moon. However, new observations of the levels of metals on our companion world suggest this origin story may need updating. Roughly 4.5 billion years ago, Theia — a Mars-sized world — is thought to have collided with the upper crust of the Earth, a region of our planet relatively poor in metals. This impact kicked large quantities of material into orbit around the Earth, which coalesced into the Moon. This idea would…

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