Connections Have Been Discovered Between Earth’s Oxygen And Its Magnetic Field
For 540 million years, the ebb and flow in the strength of Earth’s magnetic field has correlated with fluctuations in atmospheric oxygen, according to a newly released analysis by NASA scientists. The research suggests that processes deep inside the Earth might influence habitability on the planet’s surface.
Earth’s magnetic field arises from the flow of material in the planet’s molten interior, which acts like a giant electromagnet. The flow isn’t perfectly stable, and this causes the field to change over time.
Many scientists have argued that the magnetic field is crucial for protecting the atmosphere from eroded by energetic particles coming from the Sun. But, the authors of the study in Science Advances point out, the role of magnetic fields in preserving the atmosphere is an area of active research.
Before addressing the complexity of the cause-and-effect relationship between magnetic fields and oxygen levels, the study authors decided to see whether Earth’s magnetic field and atmosphere have fluctuated in ways that demonstrate a link.
Time variations of the oxygen (O2) content and the VGADM in the past 540 million years.
(A) Time series of O2 (blue) and VGADM (red). The solid lines are the mean values, and the banded regions are the data uncertainties. The dashed lines are linear trends. (B) Scaled power spectra of the detrended mean O2 and the detrended mean VGADM. The spectra are scaled by their corresponding strongest mode. — Science
The history of the Earth’s magnetic fields is recorded in magnetized minerals. When hot minerals that rise with magma at gaps between spreading tectonic plates cool down, they can record the surrounding magnetic field. The minerals retain the field record as long as they are not reheated too severely.
Scientists can deduce historic oxygen levels from ancient rocks and minerals because their chemical contents depend on the amount of oxygen available when they were formed. Data for both Earth’s magnetic field and oxygen extend over comparable ranges in databases that myriad geophysicists and geochemists have compiled. Until now, the authors of the new study say, no scientists had made a detailed comparison of the records.
“These two datasets are very similar,” said coauthor Weijia Kuang, a geophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Earth is the only known planet that supports complex life. The correlations we’ve found could help us to understand how life evolves and how it’s connected to the interior processes of the planet.”
When Kuang and colleagues analyzed the two separate datasets, they found that the planetary magnetic field has followed similar rising and falling patterns as oxygen in the atmosphere for nearly a half billion years, dating back to the Cambrian explosion, when complex life on Earth emerged.
“This 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 study coauthor Benjamin Mills, a biogeochemist at the University of Leeds.
The researchers hope to examine longer datasets to see if the correlation extends farther back in time. They also plan to investigate the historic abundance of other chemicals essential for life as we know it, such as nitrogen, to determine whether they also support these patterns. As for the specific causes linking the Earth’s deep interior to life on the surface, Kopparapu said: “There’s more work to be done to figure that out.”
Earth is the only known rocky planet to support complex life forms that use oxygen and to have a strong intrinsic magnetic field in much of its history, prompting speculation that Earth’s magnetic field and habitability are related on geological timescales. We search for possible observational evidence for such a relationship by examining evolutions of the virtual geomagnetic axial dipole moment and the atmospheric oxygen level over the past 540 million years.
We find that both exhibit strong linearly increasing trends, coupled with a large surge in magnitude between 330 and 220 million years ago. Our time series analysis and statistical tests show that both are highly correlated, with the maximum correlation reached when there is no time lag between the two. Our findings suggest unexpected strong connections between the geophysical processes in Earth’s deep interior, the surface redox budget, and biogeochemical cycling.
- Strong Link Between Earth’s Oxygen level and geomagnetic dipole revealed since the last 540 million years, Science Advances (open access)
- Strong link between Earth’s oxygen level and geomagnetic dipole revealed since the last 540 million years, Science Advances via PubMed (open access)
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