Iron atoms in motion in the Earth’s solid core

Iron atoms in motion in the Earth’s solid core

2023-10-03 18:19:26

Charged ions interacting with Earth’s magnetic field often create auroras near the planet’s poles. The aurora australis or the “southern lights” are captured here by a NASA satellite. -NASA EARTH OBSERVATORY.


The iron atoms that make up Earth’s solid inner core are tightly bound together by astronomically high pressures. But they still have room for maneuver.

A study led by the University of Texas (UT) at Austin and collaborators in China found that certain groups of iron atoms in that region of the inner core can move quickly, changing their places in a fraction of a second while maintaining the underlying metallic structure of the iron, a type of movement known as “collective movement” which is similar to when dinner guests change seats at a table.

The results, which were based on laboratory experiments and theoretical models, indicate that atoms in the inner core They move much more than previously thought.

The results could help explain numerous intriguing properties of the inner core that have long puzzled scientists, as well as help shed light on the role the inner core plays in driving Earth’s geodynamo, the elusive process that generates the planet’s magnetic field.

“We now know the fundamental mechanism that will help us understand the dynamic processes and evolution of the Earth’s inner core,” he said. it’s a statement Jung-Fu Lin, a professor at UT’s Jackson School of Geosciences and one of the study’s lead authors.

The study was published in the journal Proceedings of the National Academy of Sciences.

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It is impossible for scientists to directly sample Earth’s inner core due to its extremely high temperatures and pressures. So, Lin and his collaborators recreated it in miniature in the laboratory taking a small iron plate and shooting it with a fast-moving projectile. The temperature, pressure and velocity data collected during the experiment were then put into a machine learning computer model of atoms in the inner core.

Scientists believe that the iron atoms in the inner core are arranged in a repeating hexagonal configuration. According to Lin, most computer models depicting the lattice dynamics of iron in the inner core show only a small number of atoms, typically less than one hundred. But using an AI algorithm, the researchers were able to significantly strengthen the atomic environment, creating a “supercell” of about 30,000 atoms to more reliably predict the properties of iron.

At this supercell scale, scientists observed groups of atoms moving around, changing places while maintaining the overall hexagonal structure.

The researchers said atomic motion could explain why seismic measurements of the inner core show a much softer and more malleable environment than would be expected at such pressures, said co-senior author Youjun Zhang, a professor at Sichuan University.

“Seismologists have discovered that the center of the Earth, called the inner core, is surprisingly soft, sort of like butter in the kitchen,” he said. “The big discovery we have found is that solid iron becomes surprisingly soft deep in the Earth because its atoms can move much more than we ever imagined. “This greater movement makes the inner core less rigid and weaker against shear forces.”

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The researchers said the search for an answer to explain the physical properties “surprisingly soft” reflected in the seismic data is what motivated their research.

According to the researchers, about half of the geodynamo energy generated by Earth’s magnetic field can be attributed to the inner core, while the outer core makes up the rest. New insights into inner core activity at the atomic scale can help inform future research into how energy and heat are generated in the inner core, how it relates to the dynamics of the outer core, and how they work together to generate the magnetic field. of the planet, which is a key ingredient for a habitable planet.

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