Unusual feature of Earth’s magnetic field could explain how our planet was formed

According to a new scientific assessment, a peculiar property of Earth’s magnetic field could help us to work out how the planet formed 4.5 billion years ago.

Most theories about how the Earth and the Moon formed involve a giant impact. Examples include an impacting object striking Earth and an energetic collision that leads to the impactor and Earth being vaporised.

Now, scientists at the University of Leeds and the University of Chicago have analysed the dynamics of fluids and electrically conducting fluids. They concluded that Earth’s magnetic field must have formed either before the impact, or as a result of it.

The research, titled ‘How was the Earth-Moon system formed? New insights from the geodynamo,’ were published in the journal PNAS.

Discovering an important connection

The researchers claim that their study can help to narrow down the theories of the Earth-Moon formation, informing future research into what really happened.

Professor David Hughes, an applied mathematician in the School of Mathematics at the University of Leeds, said: “Our new idea is to point out that our theoretical understanding of the Earth’s magnetic field today can actually tell us something about the very formation of the Earth-Moon system.

“At first glance, this seems somewhat surprising, and previous theories had not recognised this potentially important connection.”

This new theory is based on the resilience of Earth’s magnetic field, which is maintained by a rotating and electrically conducting fluid in the outer core, known as a geodynamo.

Professor Fausto Cattaneo, an astrophysicist at the University of Chicago, said: “A peculiar property of the Earth’s dynamo is that it can maintain a strong magnetic field but not amplify a weak one.”

Future Earth formation models must include magnetic field evolution

The scientists concluded that if Earth’s field were to get switched off, or even reduced to a very small level, it would not have the capability to kick in again.

“It is this remarkable feature that allows us to make deductions about the history of the early Earth –including, possibly, how the Moon was formed,” stated Professor Cattaneo.

Professor Hughes added: “And if that is true, then you have to think, where did the Earth’s magnetic field come from in the first place?

“Our hypothesis is that it got to this peculiar state way back at the beginning, either pre-impact or as an immediate result of the impact.

“Either way, any realistic model of the formation of the Earth-Moon system must include magnetic field evolution.”

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