Unlike the Earth, the moon today has no magnetic field, but the lunar rocks that were collected during the 1969 Apollo 11 mission are magnetized.
Scientists speculate that this could be a signature of a planet-like process where the moon had an ancient dynamo swirling in its core, which created a magnetic field, or it could be the effect of outside forces, such as the impact of asteroids and other celestial objects on the lunar surface, which sparked electrically charged plasma that created strong but brief magnetic fields.
New scientific techniques and technologies, however, offer a growing number of evidence that the moon had a magnetic core like the Earth's. The flowing metal in our planet's core effectively makes the Earth's heart a magnetic field-producing dynamo, which plays a crucial role in ensuring the habitability of our planet.
Over the past six years, analyses of rocks collected by NASA's scientists from the moon's surface four decades ago have provided strong evidence that the Earth's natural satellite once had a magnetic field produced by an ancient dynamo in its core. Findings of a new research even suggest that this magnetic field was stronger than the Earth's today.
For their study published in the journal Science on Dec. 5, Benjamin Weiss from the Massachusetts Institute of Technology and Sonia Tikoo from the University of California, Berkeley reviewed scientific data on the moon's dynamo and confirmed that 4.25 to 3.56 billion years ago, the moon had a magnetic field produced by a molten liquid core.
The researchers also noted that this magnetic field was stronger than the magnetic field of the Earth today. Weiss said that the magnetic field of the Earth currently has the strength of 50 microteslas, but the early moon may have had a stronger magnetic field possibly reaching over 70 microteslas.
"New laboratory and spacecraft measurements strongly indicate that much of this magnetization is the product of an ancient core dynamo," the researchers wrote. "The dynamo field persisted from at least 4.25 to 3.56 billion years ago (Ga), with an intensity reaching that of the present Earth. The field then declined by at least an order of magnitude by ∼3.3 Ga."
With the confirmation of a lunar dynamo, researchers are now up to answering new questions, such as how the Earth's natural satellite had a seemingly very strong magnetic field given its very small core, and when this dynamo exactly turned off. Answers to such questions could be crucial in mankind's quest for habitable terrestrial worlds.