Earth’s magnetic field is crucial for life; Without it, the Sun’s radiation would destroy it all. However, a new study published in the journal Communications Earth & Environment, suggests that Earth’s magnetic field has not always been stable and everything indicates that life would not exist on Earth if that magnetic field had not collapsed almost completely 500 million years ago.
Would life exist on Earth if this had not happened 500 million years ago?Midjourney/Sarah Romero
A brief and necessary collapse
Researchers led by scientists at the University of Rochester have found a surprising record in which the Earth’s magnetic field decreased for 26 million years, 591 to 565 million years ago and that weakening marked a transformative era in the history of life on Earth.
According to experts, a brief collapse of the magnetic field could have allowed the development of the most complex life forms on the planet during the Ediacaran Periodin which complex multicellular organisms emerged, setting the stage for the explosion of life that would follow.
Records show that soft-bodied animals experienced an increase in diversification 575-565 million years ago, probably due to increased oxygen in the atmosphere and ocean; an event that coincides with the drop in the strength of the Earth’s magnetic field (which has changed direction many times over millions of years).
“Previous ideas about the appearance of the spectacular Ediacara fauna included genetic or ecological factors, but the proximity to the ultra-low geomagnetic field motivated us to review environmental issues and, in particular, atmospheric and oceanic oxygenation,” explained the Dean of Research from the Faculty of Arts and Sciences and the Faculty of Engineering and Applied Sciences and co-author of the work, John Tarduno.
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How can this be known?
The strength and direction of the magnetic field throughout Earth’s history is something that scientists can examine in rocks that preserve a record of the local magnetic field at the time they were formed; That is, minerals can keep a record of the strength of the magnetic field at that moment, thanks to the magnetic particles they contain.
Therefore, the researchers explored a sample of plagioclase crystals from the Fabiana Gabbros Pass, Brazil, deposited 591 million years ago. What they found was evidence of the lowest magnetic field ever recorded, one-thirtieth the level we have today. And also with a lot of difference compared to previous dates. The magnetic field was only 3% of the intensity it has today.
In essence, the magnetic field was in a very unusual state when macroscopic animals thrived and diversified. Let us remember that the Ediacara fauna was the first complex life form on Earth.
Earth’s magnetic field has changed direction many times over millions of yearsMidjourney/Sarah Romero
“They were notable for their resemblance to early animals; some even reached more than one meter (three feet) in size and were mobile, indicating that they probably needed more oxygen compared to earlier life forms,” Tarduno clarifies.
The curious thing is that it was long thought that the weak magnetic field would have been harmful to previous life forms due to exposure to constant radiation and solar winds. This does not seem to be what happened with the Ediacara fauna, prehistoric species that They flourished between 600 and 540 million years ago.
Tarduno’s team suggests that the increase in the percentage of oxygen may have been caused by the escape of atmospheric hydrogen through the Earth’s weakened shield. This allowed life to thrive thanks to it lasting a short time, of course. Researchers previously discovered that the geomagnetic field regained strength during the later Cambrian Period, when most animal groups begin to appear in the fossil record. If the weakened state of the magnetic field had remained much longer, it is possible that all the water on Earth would have vanished over time and Our planet could have become a dry place like Mars.
“If the extraordinarily weak field had remained after the Ediacara, the Earth could look very different from the water-rich planet it is today: the loss of water could have gradually dried the Earth,” the expert clarifies.
Artist’s impression of the Ediacara periodIllustration by the University of Rochester / Michael Osadciw
And why did the magnetic field decrease so much?
Scientists don’t know. Perhaps if we one day find life on other planets we can unravel this dilemma that eludes us.
References:
- Wentao Huang, John A. Tarduno, Tinghong Zhou, Mauricio Ibañez-Mejia, Laércio Dal Olmo-Barbosa, Edinei Koester, Eric G. Blackman, Aleksey V. Smirnov, Gabriel Ahrendt, Rory D. Cottrell, Kenneth P. Kodama, Richard K . Bono, David G. Sibeck, Yong-Xiang Li, Francis Nimmo, Shuhai Xiao, Michael K. Watkeys. Near-collapse of the geomagnetic field may have contributed to atmospheric oxygenation and animal radiation in the Ediacaran Period. Communications Earth & Environment, 2024; 5 (1) DOI: 10.1038/s43247-024-01360-4
