Privileged Planet: early magnetic field II (Introduction)

by David Turell , Friday, May 10, 2024, 17:41 (10 days ago) @ David Turell

A new study:

https://www.sciencenews.org/article/weaker-magnetic-field-marine-life-big

"Earth’s magnetic field protects life from harmful cosmic radiation. But sometime between about 590 million and 565 million years ago, that security blanket seems to have been much thinner — with far-reaching effects for the development of life on Earth, researchers suggest.

"A weaker magnetic field could account for the higher levels of oxygen recorded in the Earth’s atmosphere and oceans around that time — and for the ensuing proliferation of macroscopic marine animals, the team reports in the May 2 Communications Earth & Environment.

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"Now, the same team has examined rocks from Brazil dating to about 590 million years ago. Earth’s magnetic field was even weaker back then, the researchers found — just one-thirtieth the modern-day value. That’s the lowest magnetic field strength ever measured for our planet, Tarduno says. “The field almost completely collapsed.”

"If Earth’s magnetic field remained low during the roughly 25-million-year interval bracketed by those samples — and less-precise data from other teams suggest that it did — that’s a remarkable coincidence, Tarduno says. Earth’s magnetic field was dramatically weaker right around the time of the Ediacaran Period, when oxygen levels increased in both the atmosphere and oceans; rock records show higher-than-normal levels of oxygen around that time. It’s also a period when macroscopic animals began to proliferate in the world’s oceans.

"Perhaps there’s a link there, Tarduno and his colleagues propose in the new paper. A weaker magnetic field would have meant less protection from energetic cosmic particles. “Our shield was down,” Tarduno says. Those particles would have broken apart water molecules in the early Earth’s atmosphere. Hydrogen, being extremely light, would have readily escaped into space, while oxygen would have remained behind. Over time, that imbalance would have tipped the scales in favor of a more oxygen-rich atmosphere and oxygen-enriched oceans, the researchers suggest.

"The larger, more mobile animals that the fossil record shows developed during the Ediacaran Period would have needed all that oxygen, Tarduno and his collaborators suggest. It’s no secret that bigger animals require more oxygen than their microscopic brethren, Tarduno says. “This oxygenation set the stage for large life.'”

Comment: It seems our magnetic field plays a dynamic role in its pervasive influence on life at all times.