Earth's Core Possibly Formed Like a Morning Espresso, Study Suggests

By recreating the intense pressures and temperatures found deep within the Earth, scientists from the University of Stanford have uncovered evidence in support of a theory proposed 50 years ago, which states that the Earth's iron-rich core and layered internal structure formed in a series of steps over millions of years.

Published in the journal Nature Geoscience, the theory describes a process similar to how water trickles through coffee grinds to create a morning espresso, and helps to explain how Earth evolved from a messy mass of rock and metals billions years ago to the neat and orderly layers that comprise it today.

The process is called percolation and, according to lead author Wendy Mao, an assistant professor of geological and environmental sciences at Stanford, represents a viable explanation regarding the formation of the Earth's core.

Mao, who also teaches photon sciences at SLAC National Accelerator Laboratory, teamed up with researchers from the US Department of Energy's SLAC facility to recreate a small amount of the molten silicate and iron material believed to exist deep within the nascent Earth.

By using X-ray tomography and a state-of-the-art X-ray microscope, the scientists were able to observe previously unseen details in regards to changes in the texture and shape of the molten iron and silicates when placed under the same pressures and temperatures present inside the early Earth.

In doing so, they found that the molten iron formed blobs in the upper mantle -- a theory outlined in previous studies. However, while this would have seemingly prevented percolation from occurring, the team further discovered that, under such extreme pressures and temperatures, the silicates' structures changed so as to allow for connections to form between pockets of molten iron, making percolation possible.

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