Earth’s Hidden ‘Innermost-Inner’ Core –“May Reveal an Unknown, Dramatic Event in the Planet’s History”

Earth's Innermost Core


“We found evidence that may indicate a change in the structure of iron, which suggests perhaps two separate cooling events in Earth’s history,” said Joanne Stephenson, a researcher from The Australian National University (ANU),  about the confirmation of the existence of the Earth’s “innermost inner core” that may point to an unknown, dramatic event in the Earth’s history.

Still a Mystery

“The details of this big event are still a bit of a mystery, but we’ve added another piece of the puzzle when it comes to our knowledge of the Earths’ inner core,” she added. Investigating the structure of the inner core can help us understand more about the Earth’s history and evolution.

Scientists including Isaac Newton used calculations of Earth’s total density, gravitational pull and magnetic field to probe the core and mantle.

A Radius 3/4s of the Moon

“Traditionally we’ve been taught the Earth has four main layers: the crust, the mantle, the outer core and the inner core,” Stephenson explained. The inner iron and nickel core is almost as hot as the surface of the sun, with a radius about three-quarters that of the moon, located some 6,400 to 5,180 kilometers (4,000 to 3,220 miles) beneath Earth’s surface that spins a faster than the rest of the planet. Pressures at the core are over 3 million times greater than on Earth’s surface.

Search Algorithm Unveils Its Existence

The idea of another distinct innermost layer composed almost entirely of iron, says Stephenson, “was proposed a couple of decades ago, but the data has been very unclear. We got around this by using a very clever search algorithm to trawl through thousands of the models of the inner core. It’s very exciting—and might mean we have to re-write the textbooks.”

Source: J. Stephenson et al. Evidence for the Innermost Inner Core: Robust Parameter Search for Radially Varying Anisotropy Using the Neighborhood Algorithm, Journal of Geophysical Research: Solid Earth (2020). DOI: 10.1029/2020JB020545

Avi Shporer, formerly a NASA Sagan Fellow at the Jet Propulsion Laboratory (JPL) currently with the MIT Kavli Institute for Astrophysics and Space Research via  Australian National University

Image credit: Shutterstock License


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