In grade school, we’re taught that the Earth consists of four layers: the crust, the mantle, the outer core and the inner core, but a new study published by researchers from the Australian National University (ANU) suggest that our home planet may contain a hidden fifth layer.

What’s going on?

The notion of a possible fifth layer was first introduced decades ago, TNW reports, and ANU’s recent analyses of seismic waves that were sent to the Earth’s core provide evidence to support the theory.

According to TNW, researchers have dubbed this new layer the “innermost inner core” and, when it comes to size, the layer is approximately half the diameter of Earth’s inner core, Futurism reports.

“We found evidence that may indicate a change in the structure of iron,” Ph.D. researcher Joanne Stephenson stated (via Forbes). According to the site, the changes were discovered about 3,600 miles from Earth’s surface (around 400 miles from Earth’s center according to TNW).

Futurism reports that the innermost inner core features iron crystals that extend in an east-to-west direction, whereas the inner core has similar crystals that point in a north-to-south direction. According to the site, this discovery is still puzzling researchers.

Looking ahead

According to Live Science, researchers are now working with mineral physicists and geodynamicists to try to created models of the inner-inner core.

Dr. Stephenson expressed to Live Science that it’s important to understand the Earth’s core and its behaviors as they influence Earth’s magnetic field, which shields the planet from charged particles that stream from the sun. According to the site, such protection enables continued development and evolution of life on Earth.

Futurism reports that Dr. Stephenson believes further analysis of the innermost inner core could yield significant implications and broaden our understanding of the planet we call home.

“It’s very exciting,” Stephenson said (via TNW), “and might mean we have to re-write the textbooks!”