Earth’s magnetic field was formed in the first billion years of the planet’s existence. At least, that’s what recently discovered evidence suggests. The revelation is crucial as it comes closest to answering the long-debated question about the origin of Earth’s magnetic field and its correlation with the planet’s early formation.
For those in a hurry:
- Newly discovered evidence suggests that Earth’s magnetic field was formed within the first billion years of the planet’s existence. This offers crucial insights into understanding its origin and correlation with the planet’s early formation;
- The magnetic field is essential to protect the Earth from solar radiation. Therefore, it is fundamental for the formation and maintenance of life. So much so that the existence and strength of these fields on other rocky planets remains a debated and crucial question for the possibility of advanced life elsewhere in the galaxy;
- Scientists have found clues in the banded iron formations of the Isua Supracrustal Belt in Greenland, where magnetite in rocks aligns according to the direction of the magnetic field. These orientations, confirmed to be original and unaltered by reheating, provide valuable records of the strength and direction of the ancient magnetic field;
- Research led by Professor Claire Nichols from the University of Oxford points out that convective movements in Earth’s liquid outer core may have occurred before the formation of the solid core, suggesting that the magnetic field predates multicellular life. These findings have significant implications for understanding the heat that escaped the Earth’s core and how it influenced volcanic activity and the planet’s geological and biological development.
The Earth’s magnetic field partially protects the planet from solar radiation. Therefore, it is considered essential for the formation and maintenance of life. While giant planets like Jupiter have powerful magnetic fields, the prevalence of these fields on rocky planets is still a matter of debate. To give you an idea, the rarity or weakness of these fields could limit the possibility of advanced life on other planets in the galaxy.
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The study that points to the evidence in question, published in the Journal of Geophysical Research: Solid Earth, offers fundamental insight into the Earth’s magnetic history and its implications for the planet’s geological and biological evolution.
Origins of Earth’s magnetic field
The search for the origins of Earth’s magnetic field has been a priority for geologists. The rocks may preserve evidence of the field’s formation, but that evidence could be lost if the rocks heat enough to change the orientation of internal iron particles. Now, scientists have found clues in some of the oldest and most preserved rocks on the planet.
The Isua Supracrustal Belt in West Greenland is composed of some of the earliest continental crustal material and has parts that have remained relatively unchanged by geological processing. This region, despite being one of the most inhospitable places for field research, has proven to be fundamental to better understanding Earth’s magnetic history.
The banded iron (rock type) formations of the Isua Belt show the direction and, to some extent, the intensity of the magnetic field during its formation. Magnetite (the most important ferromagnetic mineral in nature and present in igneous, sedimentary and metamorphic rocks) in these formations aligns itself in the direction of the magnetic field, similar to iron filings around a magnet.
Inside the magnetic field
Professor Claire Nichols, from the University of Oxford, led the research and is confident that these guidelines are original and not the result of later reheating. Claire expressed excitement at confirming the presence of primary magnetic signals in the analyzed samples.
“Extracting reliable records from rocks this old is extremely challenging,” she said, in an interview with IFLScience. The importance of these signals is amplified by the possibility that they help understand the role of the ancient magnetic field in the emergence of life on Earth.
It is still not completely understood what causes the Earth’s magnetic field. But it is known to arise from movements in the Earth’s liquid outer core. These convection movements, driven by the solidification of the inner core, work like a dynamo that sustains the magnetic field.
The rocks studied by Nichols and his team indicate that such convective movements may have occurred even before the formation of the solid core. These findings suggest that the magnetic field is likely older than multicellular life, having implications for how much heat escaped Earth’s core early and how this influenced the mantle and volcanic activity.
