Several theories about how the Earth and the Moon were formed, most involving a giant impact. They vary from a model where the impacting object strikes the newly formed planet with a glancing blow and then escapes through to one where the collision is so energetic that both the impactor and the planet are vaporized. Now, it looks like Earth’s magnetic field played a role in Earth’s formation.
Scientists at the University of Leeds and the University of Chicago have analyzed the dynamics of electrically conducting fluids and concluded that Earth must have been magnetized before the impact or as a result.
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What role did Earth’s magnetic field play in its formation?
They claim this could help to narrow down the theories of the Earth-Moon formation and inform future research into what 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 tell us something about the formation of the Earth-Moon system. At first glance, this seems somewhat surprising, and previous theories had not recognized this potentially important connection.”
This new assessment, published in Proceedings of the National Academy of Sciences (PNAS), 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.”
The scientists, therefore, concluded that if Earth’s magnetic field were to get switched off, or even reduced to a minimal level, it would not have the capability to kick in again. Professor Cattaneo said:
“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.”
Professor Hughes added:
“And if that is true, then you have to think, where did the Earth’s magnetic field come from first? We hypothesize 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.”
Provided by the University of Leeds [Note: Materials may be edited for content and length.]