A new study suggests the Earth’s inner core isn’t a normal solid but composed of a solid iron sublattice and liquid-like light elements in a superionic state.
Earth's core the deepest part of our planet is characterized by extremely high pressures and temperatures. It's composed of a liquid outer core and a solid inner core. The inner core is formed and grows through the solidification of liquid iron at the inner core boundary.
Previous studies have shown that the inner core is less dense than pure iron and some light elements are believed to be present. But there are still a lot of questions to answer.
Now a new study suggests the earth's inner core isn't completely solid but instead is composed of a solid iron sublattice and a mixture of liquid-like light elements in a superionic state.
A superionic state is a sort of intermediate step between a solid and a liquid. And in the case of the earth's solid inner core, it's highly diffused in iron sublattices under the sorts of extreme pressures and temperatures which exist in that environment.
The findings reported in the journal Nature, are based on new high pressure and high-temperature computational simulations using quantum mechanical theories.
The authors found that some iron hydrogen, iron-carbon and iron oxygen alloys, transformed into a superionic state under the sorts of high pressures and temperatures which exist in the earth's inner core.
In superionic iron alloys, light elements become disordered and diffuse like a liquid in the lattice. While the iron atoms remain ordered and vibrate about their lattice grid, forming a solid iron framework.
One long-standing mystery about the inner core is that it's quite soft with a low sheer weight velocity. And so the authors calculated the seismic velocities in these superionic iron alloys and found a significant decrease in shear wave velocity.
And so the theoretical results fit in nicely with seismological observations. The authors say it's the liquid-like elements that make the inner core soften. That's because the highly diffused light elements can affect seismic velocities.
In the process, they're providing critical new clues for understanding other mysteries about the earth's inner core.
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