Network of Melted Iron Helped Create Ancient Earth's Core

Our Earth contains intense pressures and temperatures deep within its core. Because these conditions are so deep beneath the surface, though, scientists are still working on finding out exactly what processes occur. Now, they've discovered a little bit more about Earth's core and their findings may complicate theories of how our planet was formed.

"We know that Earth today has a core and a mantle that are differentiated," said Wendy Mao, one of the researchers, in a news release. "With improving technology, we can look at different mechanisms of how this came to be in a new light."

Earth's innards are divided into layers. There's the rocky mantle, which is composed mostly of silicates, and an iron-rich metallic core. How our planet came to have this orderly arrangement, though, is a major mystery. This is especially so because scientists believe our Earth had both messy and chaotic beginnings about 4.5 billion years ago.

There are a few theories as to how Earth evolved. One idea is that the heat generated by the collisions and by the radioactive decay of certain isotopes warmed Earth. The planet became so hot that its rocks and metals melted and then separated into distinct layers due to their different densities.

Other scientists have proposed that even if the early Earth's temperature was not hot enough to melt silicates, the molten iron might still have separated out by percolating through the solid silicate layer. More specifically, pockets of molten iron trapped in the mantle layer could tunnel through the surrounding rock to create channels, or capillaries. This network of tunnels could have helped funnel molten iron toward the planet's center to join the spherical heart already forming there. Yet this percolation theory was dealt a major blow when researchers found that in the upper mantle, molten iron tended to form isolated spheres that didn't interact with one another.

Now, scientists have discovered a little bit more about Earth formation. The researchers recreated a speck of the molten silicate and iron material that might have once existed deep inside the early Earth. They placed minute amounts of iron and silicate rock into a metal chamber that they then inserted between the tips of two small diamonds before squeezing them together.

In the end, the scientists found that while molten iron in the upper mantle tended to form isolated blobs, something else happened in the lower mantle. With higher temperatures and pressures, the structure of silicates changed in a way that permitted connections to form between pockets of molten iron, making percolation possible.

"Scientists had said that this theory wasn't possible, but now we're saying, under certain conditions that we know exist in the planet, it could happen," said Mao in a news release. "So this brings back another possibility for how the core might have formed."

The findings are published in the journal Nature Geoscience.