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Did the Moon ever have a strong magnetic field? Here’s what modern geophysics tells us

todayAugust 6, 2021 3

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Surrounding Earth is a powerful magnetic field created by swirling liquid iron in the planet’s core. Earth’s magnetic field may be nearly as old as the Earth itself – and stands in stark contrast to the Moon, which completely lacks a magnetic field today.

But did the Moon’s core generate a magnetic field in the past?

In the 1980s, geophysicists studying rocks brought back by Apollo astronauts concluded the Moon once had a magnetic field that was as strong as Earth’s. But a robust magnetic field requires a power source, and the Moon’s core is relatively small. For decades, scientists have struggled to resolve this conundrum: how could such a small core create a strong magnetic field?

I’m a professor of geophysics and have been studying Earth’s magnetic field for more than 30 years. I recently assembled a team to use new scientific techniques to reexamine the evidence for lunar magnetization. We found that the Moon did not in fact have a long-lived magnetic field. Not only does this finding change the modern understanding of the Moon’s geologic history, it also has major implications for the presence of resources on the Moon that could be critical to future human exploration.