Huge impact of space rock may have caused Earth’s magnetic field
Our planet’s magnetic field is a child prodigy, not a late bloomer, a new study suggests.
the protective magnetic field surrounding Soil is so strong that it must have formed early in our history, but there is a complication to the timing that: the earth was probably struck by a Mars-size protoplanet 4.5 billion years ago. That crash may be related to how our magnetic field was formed.
“Previous theories had failed to recognize this potentially important connection,” said study co-author David Hughes, an applied mathematician at the University of Leeds. in a statement (opens in new tab) of the peer-reviewed study in PNAS (opens in new tab)published on Wednesday (November 2).
The interplanetary collision was so colossal that it created blobs of material that… formed from the earth Moon, according to the “giant impact hypothesis” of the moon’s origin story. Scientists have studied isotopes (types of elements), meteorites and geology decades to limit the formation of the moon, but the magnetic field hypothesis has not been explored as thoroughly.
Related: Earth’s moon had a magma ocean for 200 million years
The Earth generates its magnetic field through a geodynamo process, in which a planet has to rotate at a certain speed and has an internal fluid that can conduct electricity, among other things. The Earth’s outer core of molten iron is where the conversion to electrical and magnetic energy takes place.
The field is self-perpetuating because the magnetic field induces electric currents and the currents generate a magnetic field. But how that process started in the first place is poorly understood. In their paper, the authors say these are important questions to ask in future research to determine whether the strong field existed before or after the impact:
- What are the conditions under which disk accretion leads to the formation of a highly magnetized protoplanet?
- What types of impact will leave a liquid core highly magnetized? • Conversely, what types of impact can lead to strong magnetization of the liquid core?
- Could the removal of the crust and/or mantle by a giant impact create the conditions for powerful convection in the core?
- Can the instabilities caused by rapid loss of angular momentum? [loss of rotational speed] lead to strong magnetization of the nucleus?
- Can the recondensation of accretion tori [in other words, the coming together of the donut-shaped accretion disk after the impact] lead to dynamo action?
There’s too little information at this point to choose between the scenarios, the authors point out, but they add that the great crash cannot be ignored when discussing how Earth’s magnetic field formed.
The field is linked to the relatively fast rotation of the Earth (24 hours), which is essential to keep the magnetism alive. The alternator only works if maintained, the researchers said, and cannot be restarted due to physical limitations in the Earth’s interior. However, it’s unclear whether the impact caused the dynamo or whether the Earth’s rotation earlier in history created a strong dynamo — one strong enough to withstand the impact. More research will be needed to narrow down the timing.
“It is this remarkable property [of dynamo persistence] that allows us to draw conclusions about early Earth history — including possibly how the moon formed,” lead author Fausto Cattaneo, an astrophysicist at the University of Chicago, said in the same statement.
The authors added that keeping this dynamo limitation in mind could help future researchers determine the timing of Earth’s magnetic field, either before or after the impact. They also call for more studies that delve deep into Earth’s magnetic history.
Elizabeth Howell is the co-author of “Why am I taller? (opens in new tab)?” (ECW Press, 2022; with Canadian astronaut Dave Williams), a book on space medicine. Follow her on Twitter @howellspace (opens in new tab). follow us on twitter @Spacedotcom (opens in new tab) or facebook (opens in new tab).
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