Deep underneath our feet lies Earth's outer core, a fluid layer over two thousand kilometers (1,500 mi) in thickness. Sandwiched between the planet's mantle and solid inner core, this super-hot structure is made of molten metal such as iron and nickel.
Seismic waves measured from earthquakes and volcano activities have been providing scientists information about the inner structure of our planet. But the movement of these acoustic waves is highly dependent on the property of the medium and the depth of their origins, thereby posing a restriction on how much information seismologists can obtain through seismic observations.
In a recent report, scientists at the University of Tokyo described their simulation of the Earth's center using a diamond anvil. For the first time in history, a tiny sample of liquid iron was compressed and maintained under the ultra-high pressure and temperature for a substantial period in a lab environment.
The Japanese researchers probed the iron sample with a highly focused synchrotron X-ray source and measured its density. They found that the compressed liquid iron specimen is about 8% denser than the outer core, whose density was estimated from previous studies. This evidence suggests that the molten outer core is likely to include lighter elements that have yet been identified.
The new finding regarding the core's composition could have significant implications for its movement. By combining the anvil-based measurement with mathematical modeling, this study represents a brand new approach to explore Earth's inner structure and improves our understanding of what's underneath its surface.
This study is published in the journal Physical Review Letters.
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