In a real center-of-a-Tootsie Pop situation, we may not ever know how inner Earth’s inner core really is. But it’s more than you think.

In a new study published in Nature Communications, a pair of researchers from the Australian National University in Canberra say they’ve found an “innermost inner core” for Earth, a roughly 400-mile thick innermost ball comprised of mainly iron.

This is smaller and separate from what has long been held as Earth’s inner core tradition.Earth’s inner core, believed to be a 762-mile mix of iron and nickel that makes up less than 1 percent of Earth’s volume, isn’t easy to study. Scientists have relied on waveforms reverberating from selected earthquakes along Earth’s diameter, using travel times of seismological events to model the inner core. In the new study, the pair believes that by stacking these reverberating waves from the world’s growing seismograph network, they’ve found the inner core has an outer shell that is different from the true inner core.

The studied waves offer differing angles and speeds for the inner core’s outer shell versus the now-believed distinctive innermost inner core.

The scientists also extrapolate that this finding offers a “fossilized record of a significant global event from the past.” They explain:

“Although the geomagnetic field might have preceded the inner core’s birth, detectable changes in the inner core’s structures with depth could signify shifts in the geomagnetic field’s operation, which could have profoundly influenced the Earth’s evolution and its eco-system.”

The study authors believe “proving the innermost part of the inner core is critical to further disentangling the time capsule and understanding Earth’s evolution in the distant past.”