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?
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Jesse Rogerson, PhD

Jesse is a passionate scientist, educator, and science communicator. As an assistant professor at York University in the Department of Science, Technology, and Society, he teaches three classes: History of Astronomy, Introduction to Astronomy, and Exploring the Solar System. He frequently collaborates with the Canada Aviation and Space Museum, and lends his expert voice to the Ingenium Channel. Jesse is an astrophysicist, and his research explores how super massive black holes evolve through time. Whether in the classroom, through social media, or on TV, he encourages conversations about how science and society intersect, and why science is relevant in our daily lives.