Did Earth’s magnetic field help make life possible on the planet? A new NASA-funded study suggests the answer may lie deep in geological time and the link could be stronger than once believed.
Did Earth’s magnetic field help make life possible on the planet? A new NASA-funded study suggests the answer may lie deep in geological time and the link could be stronger than once believed.
Earth is an outlier among rocky planets. It boasts a long-lasting magnetic field generated by turbulent motions in its core and an oxygen-rich atmosphere that has sustained complex life for hundreds of millions of years. Researchers have long suspected a connection between these two defining features, but direct evidence remained elusive.
Instead of focusing on dramatic, short-lived events, the new study takes a long view, examining slow-moving trends over the past 540 million years. Using existing geological records rather than theoretical models, scientists placed two independent datasets side by side — one tracking the strength of Earth’s magnetic field, the other tracing atmospheric oxygen levels. The results hint at a deep, long-term partnership shaping Earth’s habitability.
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To reconstruct the planet’s magnetic past, researchers analyzed ancient rocks that preserve faint magnetic signatures from the time they cooled. These geological “time capsules” allow scientists to estimate how strong Earth’s magnetic field was across the Phanerozoic era. Though incomplete, the record reveals broad patterns stretching across hundreds of millions of years.
Oxygen, by contrast, leaves no direct fossil record. But its chemical fingerprints linger in sediments, soils, and fossils, offering indirect clues about how much of the gas filled the atmosphere at different points in time. These proxies reveal that oxygen levels were far from stable, rising gradually overall and peaking dramatically during the late Palaeozoic era.
When researchers compared the two timelines, a striking pattern emerged. Both the magnetic field strength and atmospheric oxygen levels increased over the same vast stretches of time. Most notably, both showed a pronounced surge between roughly 330 and 220 million years ago, a coincidence that stood out because the records were derived from entirely different sources.
To test whether this alignment was merely chance, scientists ran extensive statistical simulations. Randomised datasets designed to mimic noise and uncertainty rarely reproduced the strength of the observed correlation. The strongest link appeared only when both records were aligned precisely in time, with no measurable delay between them.
However, the connection dissolved when scientists zoomed in on shorter timescales. Over spans of just a few million years, the relationship vanished, suggesting the link is not driven by sudden or catastrophic events. Instead, it appears to reflect slow, deep-Earth processes unfolding over immense geological periods.
The findings raise the possibility that Earth’s magnetic field played a quiet but critical role in stabilising atmospheric oxygen. A stronger magnetic field offers greater protection from charged solar particles that can strip gases from the atmosphere. Over hundreds of millions of years, this shielding may have reduced oxygen loss.
Beyond protection, the magnetic field is tied to movements within Earth’s core and mantle — forces that influence volcanism, weathering, and nutrient cycling. These processes, in turn, regulate how oxygen is produced and consumed. Together, they suggest a subtle but powerful continuum, in which Earth’s deep interior has supported life at the surface without dramatic signals or sudden transformations.
