Earth’s magnetic field strength and atmospheric oxygen levels have oscillated in tandem for around 540 million years, according to a NASA-led study, pointing to a deep-Earth process that could knit our planet’s life-supporting systems more tightly than previously understood.
Mapping trends from the Cambrian explosion to modern times, scientists found that periods of peak geomagnetic force—often logged in minerals as they cool within erupting magma—align closely with elevated oxygen levels, inferred from charcoal deposits and geochemical signatures in ancient rocks.
Lead author Weijia Kuang of NASA’s Goddard Space Flight Center asserts this constitutes the first statistically robust link between the magnetic dipole and atmospheric oxygen across geological time.
Rises in both parameters registered pronounced peaks during the span from around 330 to 220 million years ago—coinciding with both a supercontinent cycle and heightened wildfire evidence—suggesting an underlying mechanism shorter than the age of the planet but far-reaching in effect.
The research, appearing in Science Advances on 13 June 2025, assigns a leading role to Earth’s magnetic field in potentially preserving atmospheric oxygen. By deflecting solar and cosmic radiation, the magnetic shield may slow atmospheric erosion and guard oxygen-producing photosynthetic lifeforms from harmful radiation.
Alternate hypotheses suggest plate tectonics as a grand orchestrator. As continental drift drives crustal recycling and alters the thermal and chemical gradient at the core–mantle boundary, it may influence both geomagnetic behaviour and oxygen cycling—mirroring the oxygen flux through time.
“The correlation raises the possibility that both the magnetic field strength and the atmospheric oxygen level are responding to a single underlying process, such as the movement of Earth’s continents,” said co-author Benjamin Mills from the University of Leeds.
Despite the strong correlation—approximately 0.72 across data spanning 540 million years—uncertainty lingers over cause and effect. The team points to a negligible lag between the datasets, but concedes that whether the magnetic field drove oxygen dynamics, vice versa, or if both were shaped by tectonic activity, remains unresolved.
An intriguing outlier arose from nearly 591–565 million years ago, when a weaker geomagnetic field coincided with a dramatic oxygen spike and a surge in marine biodiversity, implying that at times other forces may dominate.
Demonstrations from Mars reinforce the protective value of a magnetic field: as its field waned around four billion years ago, atmospheric loss ensued, drying the planet’s surface and chilling its climate.
If validated, this geophysical coupling could reshape the parameters scientists use in the search for life on other rocky worlds. As Ravi Kopparapu from NASA notes, understanding this interplay is vital—and yet still in preliminary stages.
The team intends to probe further back in time, seeking whether earlier supercontinents beyond Pangaea exhibited the same synchronicity. They also aim to include other biologically relevant atmospheric constituents—such as nitrogen—to evaluate whether they too display linked fluctuations.
Collaboration across geology, geochemistry and planetary science appears essential. As Kopparapu explains: “One single mind cannot comprehend the whole system of the Earth. We’re like kids playing with Legos… trying to fit all of it together and see what’s the big picture”.