Scientists have recreated the sacred conditions in the heart of our planet in a laboratory – and now believe that the Earth’s solid core is about a billion years old, much younger than previously thought.
Researchers measure the conductivity of iron – the material that forms the Earth’s core – in nuclear-like conditions, with a pressure greater than one million atmospheres and temperatures as high as the sun’s surface.
They achieve these conditions by pressing laser-heated samples of iron between two diamond legs.
Researchers from the University of Texas at Austin now believe that the solid inner core of the planet formed between one billion and 1.3 billion years ago.
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The discovery could help scientists understand the origin of our planet’s geodynamo – the mechanism that sustains the Earth’s magnetic field, that holds compasses pointing north, and protects life from harmful cosmic rays.
Professor Jung-Fu Lin said, “People are really envious and excited about knowing the origin of the geodynamo, the strength of the magnetic field, because they all contribute to the viability of a planet.”
The study was published in the journal Physical Review Letters.
The core of our planet is made of iron, with a solid inner core and a fluid outer core. But researchers are struggling to find a theory about when the solid core formed, without requiring unrealistically high temperatures to maintain the Earth’s geodynamo.
The new research solves this paradox by finding a solution that keeps the temperature of the core within realistic parameters.
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“We have encountered many problems and failed several times, which has frustrated us, and we have almost given up,” said article-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, researchers can make a more accurate estimate of the age of the inner core.
“Once you know how much of that heat flow from the outer core to the lower mantle, you can really think about when the Earth cools enough to the point where the inner core begins to crystallize,” he said.
This revised age of the inner core could correlate with a peak in the strength of the Earth’s magnetic field, as evidenced 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 the creation of current magnetic fields.
