“One substantial hunk of junk led to the formation of the Moon. The unexpected scarcity of iron and other higher-mass elements in the Moon, derived from lunar samples returned by Apollo astronauts, indicates that the Moon most likely burst forth from Earth’s iron-poor crust and mantle after a glancing collision with a wayward Mars-sized protoplanet.”

“One substantial hunk of junk led to the formation of the Moon. The unexpected scarcity of iron and other higher-mass elements in the Moon, derived from lunar samples returned by Apollo astronauts, indicates that the Moon most likely burst forth from Earth’s iron-poor crust and mantle after a glancing collision with a wayward Mars-sized protoplanet.”

— Neil deGrasse Tyson