According to recent research, Earth's inner core may not be a solid sphere of nickel and iron as previously thought, but rather a complex structure consisting of two layers: a distinct central region surrounded by an outer shell.

Using a new type of seismic wave that travels through and bounces back and forth within the Earth's core, scientists have confirmed the existence of this innermost inner core. By analyzing seismic data from earthquakes of magnitude 6 or larger that occurred over the past decade, the researchers were able to detect faint reflections of seismic waves, with 16 events producing waves that bounced through the inner core multiple times.

The Earth's core generates the planet's magnetic field, which protects us from harmful charged particles emitted by the sun. Understanding the structure and behavior of the core is therefore crucial for the study of Earth's magnetic field and its evolution over time. The core consists of two main parts: a liquid outer core and a solid inner core. As fluid rich in iron circulates in the outer core, some of it cools and solidifies, forming a solid center. This process generates the Earth's magnetic field. However, different types and structures of minerals, as well as varying amounts of liquid in the subsurface, can affect the speed of seismic waves traveling through the Earth and provide clues to the composition of the core.

Recent seismic data have shown that seismic waves traveling through the innermost part of the Earth move slightly slower in one direction than in others, suggesting an anomaly in the crystal structure of the core. The existence of an innermost inner core was first proposed in 2002 and has been supported by subsequent independent lines of evidence.

The latest study, published in Nature Communications, provides the strongest evidence yet for the presence of this hidden heart, which may shed light on the early formation of the Earth's core and the future of the planet's magnetic field.