Earth's hiding fifth layer in its inner core, reveals fresh evidence

Fresh evidence concerning the possibility that Earth's inner core has a separate inner core of its own was published in Nature Communications on February 21.

The latest findings suggest that the 'innermost inner core' may be an iron ball with a radius of about 650 kilometers inside the inner core. This could indicate a dramatic event in our planet's history and improve our understanding of Earth's genesis and evolution.

What's the proof of Earth's innermost inner core?

In the new study, Thanh-Son Phạm and Hrvoje Tkalčić from the Australian National University collated data from existing probes. From this, they measured the different arrival times of seismic energy waves created by earthquakes as they traveled through the Earth. 

They observed for the first time the waves reverberating along the entire Earth's diameter up to five times. The travel times of the waves suggest the presence of a distinct internal shell, with a radius of approximately 650 kilometers, which is separate from the outer layer of the inner core. The authors suggest that this internal interface may reflect a past change in the inner core growth. 

They also advised that better to comprehend Earth's deep interior and its generation history, future research should concentrate on characterizing the transition between the innermost inner core and the inner core's outer shell.

How many layers does Earth have?

Traditionally we've been taught the Earth has four primary layers: the crust, the mantle, the outer core, and the inner core. 

Though Earth's solid inner core makes up less than 1 percent of Earth's total volume, it has played a significant part in our planet's evolution- particularly in the generation of Earth's magnetic field. However, since its discovery in 1936, the inner core has remained particularly enigmatic.

In fact, the idea of an additional separate layer within the inner core was put forth a few decades ago due to evidence pointing towards a change of composition (or anisotropy) at depth. 

Geophysicist Adam Dziewonski and seismologist Miaki Ishii were the first scientists to explain the discrepancies in specific fit to travel-time wave models of the Inner Core.

Still, probing the Earth's innermost inner core has been challenging due to a lack of probes sensitive enough to sample the Earth's deep interior. Additionally, the status of the innermost inner core as a distinct entity remains contested, with detractors arguing that anomalous data can be explained with other methods. 

The full study can be found here.

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