Scientists have discovered something mysterious in the Earth’s core

The ‘soft’ core conundrum

Ever since the thirties of the last century, the prevailing model of the Earth’s interior described a liquid outer core and a solid inner core, which remained rigid despite the extreme pressure. hellish heat. However, seismological data collected over the years did not fully agree with that picture. Measurements have shown that seismic waves, which scientists use as a kind of ultrasound for studying the planet’s interior, slow down as they pass through the core.

This indicated that the core was unexpectedly “soft” or pliable, like butter, rather than rigid as one would expect from a piece of iron. This anomaly has long puzzled geophysicists.

How can something be at the same time solid under a pressure of over three million atmospheres, and still behave as if it were partially liquid? The answer could lie in the so-called superionic state, an exotic form of matter that computer simulations predicted could exist in the core as early as 2022.

Now scientists have experimentally proven it for the first time.

An experiment that mimics the conditions of hell

To confirm the theory, a team led by physicist Youjun Zhang from Sichuan University designed an amazing experiment. Using a specialized two-stage gas cannon, they fired projectiles made of carbon-iron alloy at a speed of more than seven kilometers per second. Those projectiles hit the target, creating a shock wave that compressed the material sample to a pressure of up to 140 gigapascals and heated it to almost 2600 Kelvin. Although these conditions are somewhat milder than those in the core itself (330-360 GPa and up to 6000 K), they were sufficient to mimic key aspects of the environment at the center of the Earth.

The whole process lasted only a few nanoseconds, but that was enough to helpć lasers and fast sensors measure the key properties of the material. The results were astonishing: the alloy showed drastically reduced stiffness and behavior that perfectly matched the seismological data on the “soft” core.

The ‘dance’ of carbon atoms inside the žiron lattice

In the superionic state, the heavier atomic structure remains fixed in place, like a crystal lattice in a solid body, while the lighter atoms move through it almost freely, as if they were in a liquid state. In the case of the Earth’s core, this means that the iron forms a kind, stable “skeleton”, while the much lighter carbon atoms pass and flow through the gaps in that lattice.

​- In this state, the carbon atoms become extremely mobile and diffuse through the crystalline žiron structure, like children moving through a dancečin a square dance, while the žiron itself remains čsolid and ordered. This so-called ‘superionic phase’ dramatically reduces the stiffness of the alloy – Professor Zhang explained.

This dynamic model not only solves the puzzle of slow seismic waves, but also it also opens up new perspectives on other processes within the planet. The movement of lighter elements inside the core could be a hitherto neglected source of energy for the geodynamo – the mechanism that creates and maintains the Earth’s magnetic field, the shield that protects us from the sun’s harmful radiation.

Moving towards a dynamic model of the Earth

This discovery represents a fundamental change in the way scientists observe the center of our planet. Instead of a static, rigid sphere, the inner core is now seen as a dynamic and complex place where matter exists in a state that defies simple definitions.

​- We are moving away from a static, rigid model of the inner core towards a dynamic one – concludes Zhang.

Understanding this hidden state of matter brings us one step closer to uncovering the secrets of the interior of Earth-like planets, which in the future could help in the study of magnetic fields and the evolution of distant exoplanets.