A group of MIT researchers believe they have discovered the source of the moon’s magnetism, a puzzler that has baffled scientists since the 1970s when Apollo astronauts first brought moon rocks to Earth, Space.com reports.
“Earth’s rotating, iron core produces the planet’s magnetic field. But the moon does not have such a setup,” the report said. Instead, MIT scientists now believe that the Moon did in fact have a liquid core with a dynamo about 4.2 billion years ago. Most moon rocks lose their traces of magnetism when subjected to major shocks from impacts. But the scientists found their smoking gun by examining the oldest moon rock brought to Earth—by Harrison “Jack” Schmitt, the only geologist ever to walk on the moon, during the last lunar landing mission, Apollo 17, in 1972.
“Many people think that it’s the most interesting lunar rock,” said MIT’s Ben Weiss in the article; his team found traces of the original magnetic field using a commercial rock magnetometer equipped with a robotic system geared toward detecting faint traces of magnetism. The report said that the findings fit in with the prevailing theory that the moon was born when a Mars-sized body crashed into the Earth and blasted much of its crust into space, where it clumped together to form the moon.