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Moon lacked a magnetic field for nearly all its history – new research resolves mystery sparked by rocks brought back on Apollo

Scientists have studying lunar samples brought back from Apollo missions to understand the geologic history of the Moon. NASA

Moon lacked a magnetic field for nearly all its history – new research resolves mystery sparked by rocks brought back on Apollo

Scientists have studying lunar samples brought back from Apollo missions to understand the geologic history of the Moon. NASA

Moon lacked a magnetic field for nearly all its history – new research resolves mystery sparked by rocks brought back on Apollo

Scientists have studying lunar samples brought back from Apollo missions to understand the geologic history of the Moon. NASA

Moon lacked a magnetic field for nearly all its history – new research resolves mystery sparked by rocks brought back on Apollo

Scientists have studying lunar samples brought back from Apollo missions to understand the geologic history of the Moon. NASA

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.

Scientists have studying lunar samples brought back from Apollo missions to understand the geologic history of the Moon. NASA

John Tarduno, University of Rochester

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.

A diagram showing cutouts of the Earth and Moon with the Moon having a much smaller core relative to its size.

Relative to the Earth, the Moon has a small core, and it is not obvious how it could have created a strong magnetic field. Rory Cottrell/U. Rochester, CC BY-ND

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