How Could the Moon Generate a Magnetic Field?

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An image of the Moon
The Moon once had a magnetic field, but how did it generate it? (image credit: NASA/JPL/USGS)

The Earth's magnetic field is powered by an internal dynamo at the core of the planet. At the very centre of the Earth is a very hot, solid, iron core that is surrounded by an outer liquid iron region. The heat from the inner core drives convection in the outer core (hot parts of the liquid rise, cool parts fall). All the while, the core is rotating. Since the liquid outer core is a conductor, the motions of rotation and convection generates a magnetic field.

The Moon has no such magnetic field, at least not right now. Lunar rocks returned by the Apollo missions indicate a magnetic field was active there about 3 billion years ago, but how could it be generated? Given the size of the Lunar core, it was not believed there would be enough heat to drive convection. In a recent paper published in the peer-reviewed journal Earth and Planetary Science Letters, NASA scientists think they have figured out how the core of the moon could have generated enough heat and therefore convection to support a magnetic field.

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How Could the Moon Generate a Magnetic Field?
NASA
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Jesse Rogerson, PhD

As a passionate science communicator, Jesse Rogerson loves promoting science literacy to the public. He frequently represents the Canada Aviation and Space Museum on television and radio, social media, and at conferences. He co-developed a science communication workshop for Canadian science professionals, to instruct them in more effective methods of communicating their science. A trained and practicing astrophysicist, Jesse holds a PhD in observational astrophysics from York University, and recently published a peer-reviewed paper in The Astrophysical Journal. Jesse enjoys riding his motorcycle, board games, and ultimate frisbee.