The origin of Earth’s abnormally large moon is a long-standing mystery in astronomy. Most scientists believe our satellite formed from the remains of a small world called Theia after it smacked into Earth 4.5 billion years ago. Models show that chunks of the Mars-size interloper spun off and coalesced into the moon. So astronomers were puzzled when lunar samples returned by Apollo astronauts showed striking similarities to Earth rocks instead.
A moon rock recovered during the Apollo 16 mission puzzled researchers initially because its composition of a rare metal is identical to Earth's. (Credit: NASA/JSC)
NASA/JSC
In April, astrophysicists announced they’d found a possible reason: Theia was Earth’s twin. In a Nature study, scientists modeled the solar system’s birth and watched virtual worlds collide like wrecking balls. They found that Theia likely formed close to Earth and collected the same cosmic debris as it grew. It makes sense, then, that ...
