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Scientists Might Have Figured Out Why Earth's Super-Hot Core Stays Solid

Researchers have a new explanation for why Earth's inner core remains solid - despite being hotter than the Sun’s Surface. Turns out, it could be due to the atomic architecture of the crystallized iron ball at the center of Earth. Scientists propose that this iron core exists in a never-seen-before atomic state that allows it to resist the unbelievable temperatures and pressures found in the Earth’s center – and if they are right, it could crack a secret that has been puzzling scientists for decades.

Vadim Sadovski



A team from the KTH Royal Institute of Technology in Sweden used Triolith –Country's largest supercomputers – to simulate what atomic processes might be occurring some 4,000 miles (6400 kilometers)  beneath the Earth’s surface.

As with any metal, the atomic-scale structures in iron change is dependent on temperature and pressure. At NTP (normal room temperature and pressure), iron is in what's called a body-centered cubic (BCC) phase; under high pressure, it shifts to a hexagonal close packed (HCP) phase.

These practical terms explain the arrangement of atoms inside the metal, which in turn disturbs its strength and other properties, e.g. whether it stays solid or not.

So far, it was believed the solid, crystallized iron at the core of Earth was in an HCP arrangement because conditions were too unbalanced for BCC.

The new study turns that on its head, proposing that the environment at the Earth’s center, in fact, supports this BCC arrangement, rather than breaking it up.

"Under conditions in the core of Earth, BCC iron possesses an arrangement of atomic diffusion never seen before," says one of the scientists, Anatoly Belonoshko.

"The BCC phase proceeds with the motto: 'What does not kill me makes me stronger.' The instability destroys the BCC phase at low temperature, but stables the BCC phase at high temperature."

Belonoshko relates the extreme atomic activity of the iron at the Earth’s center to cards being shuffled in a deck – while the atoms might be getting shuffled extremely quickly because of the high forces of temperature and pressure but the deck remains intact.

And those forces indeed are incredible: 3.5 million times the pressure we experience at the surface, along with temperatures some 10,800°F (6000 °C) hotter than those we experience at the surface of Earth.

The data crunched by Triolith also demonstrates that 96% of Earth's inner core is probably made up of iron – a higher figure than earlier approximations, with nickel and other light elements making up the rest of the core.

Another secret that could be cracked by the latest research is why seismic waves travel faster between the poles than through the equator – a property scientifically known as anisotropy – which means something ordered in one specific direction, like grains in the wood.

The scientists say the behavior of BCC iron under the extreme conditions at the core of the Earth could be enough to create significant anisotropic effects, opening up another opportunity for researchers to explore in the future.

It's important to note that these theories are based on particular simulations of internal movements of Earth, and separate the teams running different models based on different measures could end up with outcomes that are incompatible with these assumptions.

Until we can figure out how to get genuine equipment down there, we will never be 100% sure that the readings are correct - and with the kinds of pressures and temperatures believe to exist down there, we might never have direct proof of the activity of the core.

But it's important discovery to pursue, despite the challenges, because once we know more about the inner activities of Earth, we can make better estimates about what will happen next.
Belonoshko said, "The vital goal of earth sciences is to understand the past, present, and future of the Earth, and our calculations allow us to do just that."

The findings are published in Nature Geoscience.

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