The true age of Earth's core has been discovered – and it's younger than previously thought

The finding could help us understand the 'Geodynamo' which keeps compasses pointing north (NASA)
The finding could help us understand the 'Geodynamo' which keeps compasses pointing north. (NASA)

Scientists have recreated the hellish conditions in the heart of our planet in a laboratory – and now believe Earth’s solid core is around a billion years old, far younger than thought.

Researchers measured the conductivity of iron – the material that forms Earth’s core – in core-like conditions, with a pressure greater than one million atmospheres and temperatures as high as the surface of the sun.

They achieved these conditions by squeezing laser-heated samples of iron between two diamond anvils.

The University of Texas at Austin researchers now believe that the planet’s solid inner core formed between one billion and 1.3 billion years ago.

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The finding could help scientists understand the origin of our planet’s geodynamo – the mechanism that sustains the Earth’s magnetic field, which keeps compasses pointing north and helps protect life from harmful cosmic rays.

Professor Jung-Fu Lin said: “People are really curious and excited about knowing about the origin of the geodynamo, the strength of the magnetic field, because they all contribute to a planet’s habitability.”

The research was published in the journal Physical Review Letters.

Our planet’s core is made of iron, with a solid inner core and a liquid outer core. But researchers have struggled to find a theory on when the solid core formed, without requiring unrealistically high temperatures to maintain Earth’s geodynamo.

The new research solves that paradox by finding a solution that keeps the temperature of the core within realistic parameters.

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“We encountered many problems and failed several times, which made us frustrated, and we almost gave up,” said article co-author Youjun Zhang, an associate professor at Sichuan University in China. “We finally worked it out after several test runs.”

Lin said that with this improved information on conductivity and heat transfer over time, the researchers could make a more precise estimate of the age of the inner core.

“Once you actually know how much of that heat flux from the outer core to the lower mantle, you can actually think about when did the Earth cool sufficiently to the point that the inner core starts to crystallise,” he said.

This revised age of the inner core could correlate with a spike in the strength of the Earth’s magnetic field as recorded by the arrangement of magnetic materials in rocks that were formed around this time.

The evidence suggests that the formation of the inner core was an essential part of creating today’s robust magnetic fields.

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