A new study by Nasa scientists has revealed a deep, previously unrecognised connection between the ebb and flow of Earth’s magnetic field and the rise and fall of atmospheric oxygen over the past 540 million years — a discovery that could reshape our understanding of what makes Earth habitable.

Earth’s magnetic field, generated by the swirling motion of molten iron in its core, acts as a vast shield, protecting the atmosphere from being stripped away by the relentless solar wind.

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While scientists have long speculated that this field is crucial for preserving the planet’s life-sustaining gases, direct evidence linking magnetic field strength to oxygen levels has been elusive until now.

By meticulously analysing two independent datasets — one recording ancient magnetic field strength in rocks and minerals, and the other tracking atmospheric oxygen through geochemical proxies — researchers found that the two have fluctuated in near lockstep since the Cambrian explosion, a period when complex life first flourished on Earth.

Peaks in magnetic field intensity coincided with spikes in oxygen, while troughs in one matched dips in the other, with the strongest correlation occurring with virtually no time lag.

“This is the first discovery we’ve ever had to establish the link between the geomagnetic field and the oxygen level,” said study coauthor Weijia Kuang, a geophysicist at NASA’s Goddard Space Flight Center. The findings suggest that processes deep within Earth—such as the movement of continents or changes in the core—may simultaneously influence both the magnetic field and the chemical makeup of the atmosphere.

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Not only does this research offer new clues about how Earth has maintained the delicate balance needed for life, but it may also help scientists identify the conditions necessary for habitability on other planets.

However, the exact mechanisms behind this connection remain unclear, and researchers caution that more work is needed to unravel the complex interplay between Earth’s interior dynamics and its surface environment.

As scientists probe deeper into Earth’s past, this discovery opens a fresh perspective on the forces that have shaped—and continue to sustain—life on our planet.