Researchers have been studying the very, very ancient history of the moon’s magnetic field by analyzing rocks, collected by astronauts, that are billions of years old, the Massachusetts Institute of Technology said Wednesday.
The rocks contain thousands of tiny grains that aligned in the direction of the magnetic field at the long-ago time they were formed, MIT said in a statement.
The latest research, by scientists from MIT and Rutgers University, which was published Wednesday in the journal Science Advances, indicates that the moon’s magnetic field lasted at least 1 billion years longer than previously thought, MIT said.
Magnetic fields around terrestrial bodies are created by a dynamo, the churning of the bodies’ molten metallic cores, researchers said.
Researchers now believe the moon’s magnetic field existed for a total of at least 2 billion years, though now it has dwindled away.
In their latest study, researchers focused on a rock that was between 1 and 2.5 billion years old. It was collected on Aug. 1, 1971, by Apollo 15 astronauts from the southern rim of the moon’s Dune Crater.
The rock showed indications of a much weaker magnetic field than moon rocks the researchers had previously studied that were 4 billion years old.
Researchers plan to analyze more rocks to determine when the dynamo died off completely.
“Today the moon’s field is essentially zero,” said Benjamin Weiss, a professor of planetary sciences at MIT. “And we now know it turned off somewhere between the formation of this [more recent] rock and today.”