A study published Oct. 2 by a UT professor and colleagues in China explains perplexing properties of our planet’s inner core and may help us understand what qualities make our planet habitable.

The inner core is nestled deep within the earth’s interior, bound by extreme pressure and temperature conditions, said Jung-Fu Lin, professor of geological sciences at UT and study co-lead. Lin and researchers at the National Natural Science Foundation of China found that the iron atoms that make up the core move around unexpectedly quickly.

“In the past, we didn’t really have too many ways to study [the inner core’s] properties, except seismic wave studies and geodynamics, and [researchers] have found a number of very interesting properties that are very difficult to explain,” Lin said.

For example, seismic waves unexpectedly slow down in the Earth’s inner core, Lin said, something he and his colleagues sought to understand in the study.

In order to explain these properties, Lin said he and his colleagues used a shockwave technique, which involves shooting a high-speed projectile at an iron sample, to create recordable, high-pressure conditions. With that data, the researchers then used artificial intelligence algorithms to multiply the number of atoms in order to reliably predict properties of atom movements.

Iron atoms are arranged in a solid crystal structure, Lin said. Typically, when a seismic wave travels through a solid, wave velocities are relatively high. But because atoms move around freely in the inner core, the iron becomes extremely soft and behaves more like a liquid than a solid.

“The discovery that collective motion of iron atoms occurs in the Earth’s inner core is quite exciting because it offers an explanation of why it is ‘soft’ despite being a solid at really high pressures,” said Krista Soderlund, research scientist at the University of Texas Institute for Geophysics, in an email.

Lin said the velocity of seismic waves drops significantly when they enter the soft inner core, which explains the seismic properties they previously observed.

The study findings can help scientists understand properties of our planet and others outside of our solar system, particularly the conditions needed for habitability, Lin said.

The inner core is imperative to the planet’s “dynamics, thermal evolution, core convection, and habitability,” according to the study. Namely, the inner core contributes half of the energy needed to generate the earth’s magnetic field, which is crucial to planetary habitability, Lin said.

“This [study] is important for not only understanding the properties of the inner core and how it behaves, but also how it interacts with the outer core and generates the Earth’s magnetic field,” Soderlund said in an email.