The Earth’s core is not solid: this discovery overturns everything we thought we knew

How the Earth Generates Its Magnetic Field

The Earth’s magnetic field is perhaps the most underrated defense system in history. Invisible and silent, it envelops our planet and deflects the constant stream of charged particles that the Sun spews into space. Without it, this radiation would have long since stripped away our atmosphere and sterilized the surface. Mars is living—or rather, dead—proof of this. The Red Planet lost its magnetic field billions of years ago, and with it, most of its atmosphere and liquid water. But how does Earth generate this vital shield? The answer lies in a process called the geodynamo, and the discovery of the superionic state has just rewritten its equations.

The classic geodynamo model works as follows: the Earth’s outer core, composed of liquid iron and nickel, is in constant motion. Heat escaping from the inner core creates convection currents—upward and downward movements of the molten metal. The Earth’s rotation deflects these currents, creating complex vortices. And since liquid iron conducts electricity, these movements generate a magnetic field through the dynamo effect—the same principle as an electric generator, but on a planetary scale. This model worked well, but it had one problem: calculations showed that the Earth should have lost its magnetic field long ago. The energy source seemed insufficient to sustain the geodynamo for 4.5 billion years.

A New Energy Source Discovered

This is where the superionic state changes the game. The mobility of light elements such as carbon within the inner core is not just a scientific curiosity—it is a previously unrecognized source of energy. “Atomic diffusion within the inner core represents a previously overlooked energy source for the geodynamo,” explains Dr. Huang. “In addition to heat and compositional convection, the fluid motion of light elements can help power the Earth’s magnetic engine.” ” In other words, our planet’s core is not an inert ball of iron that simply cools slowly. It is a dynamic system where light atoms circulate constantly, transferring energy and sustaining the processes that generate our protective shield.

This discovery has profound implications for our understanding of Earth’s geological history. The magnetic field has existed for at least 3.5 billion years—perhaps even since the planet’s formation. Previous models struggled to explain how Earth could have sustained its geodynamo for so long using only known energy sources. The superionic state provides a missing piece of the puzzle. The continuous diffusion of carbon atoms and other light elements through the inner core could significantly extend the geodynamo’s lifespan. Our magnetic shield may be more robust and durable than expected—reassuring news for a species that depends on it for its survival.

The Mystery of Core Anisotropy

Seismologists had long observed a strange phenomenon: seismic waves do not travel through the inner core at the same speed in all directions. This phenomenon, known as seismic anisotropy, suggests that the core is not a uniform, isotropic sphere. The waves travel slightly faster along the Earth’s axis of rotation than perpendicular to it. Why? Theories abounded, but none were entirely satisfactory. The superionic state offers an elegant explanation. If mobile light elements move preferentially in certain directions—perhaps influenced by the Earth’s rotation or by temperature gradients—they could create “corridors” of slightly different properties within the core.

Professor Yu He of the Institute of Geochemistry at the Chinese Academy of Sciences, a co-author of the study, emphasizes the importance of this connection: “We are moving from a static, rigid model of the inner core to a more dynamic one. ” This conceptual shift is fundamental. For decades, geophysicists have treated the inner core as an essentially passive object—a solidified ball of iron that was slowly cooling and releasing heat. The new model presents it as an active system, where constant diffusion processes alter its properties and interact with the liquid outer core. This paradigm shift opens up new avenues of research to understand not only the core’s structure but also its evolution over geological time.

I find it fascinating to realize that the Earth, this 4.5-billion-year-old lady on whom we live, still holds fundamental secrets. We’ve sent probes to the far reaches of the solar system, detected gravitational waves from distant galaxies, and sequenced the human genome. But the heart of our own planet remained an enigma. And it took a cannon firing projectiles at 25,000 km/h to begin unraveling this mystery. Science, at times, requires brute force as much as it does intellectual finesse.

A Revealing Poisson’s Ratio

Among the measurements that confirmed the superionic state, one in particular startled the researchers: the Poisson’s ratio. This number, which generally varies between 0 and 0.5, measures how a material deforms when compressed. A perfectly rigid material like steel has a Poisson’s ratio of about 0.3. A perfectly compressible material would have a value of 0.5. And butter? About 0.44. However, measurements taken on iron-carbon alloys under conditions similar to those in the Earth’s core yield a Poisson’s ratio much closer to that of butter than to that of steel. Hence the striking metaphor that has spread around the world: the Earth’s core is “buttery.”

This unexpected mechanical property directly explains why shear waves slow down so much as they pass through the inner core. Shear waves cause matter to vibrate perpendicular to their direction of propagation—they “shake” the material from side to side. A rigid material efficiently transmits this type of vibration. A “buttery” material absorbs some of the energy, just as your hands absorb the shock when you clap on a cushion rather than on a table. The Earth’s inner core, with its mobile carbon atoms circulating freely within the iron matrix, behaves exactly like this cosmic cushion. The structure is there, but its rigidity is compromised by the mobility of its light constituents.

Toward a New Understanding of Rocky Planets

The discovery of the superionic state at the Earth’s core is not limited to our planet. It opens a window into understanding all rocky bodies in the universe. Mercury, Venus, Mars, and the Moon—all of these worlds have or have had a metallic core. And all exhibit magnetic properties that are difficult to explain using classical models. Mercury, for example, has a weak but measurable magnetic field, even though its small size should have caused it to lose that field long ago. Mars shows traces of a former global magnetic field that has since disappeared. The potential presence of superionic states in their cores could explain some of these anomalies.

But it is perhaps in the study of exoplanets that this discovery will have the greatest impact. Thousands of planets have been discovered orbiting other stars, and many are “super-Earths”—rocky worlds more massive than our own. The pressure and temperature conditions at the cores of these planets far exceed those of Earth’s core. The superionic state could be even more pronounced there, or even give rise to entirely exotic states of matter. Understanding how these processes affect planetary magnetism is crucial for assessing the potential habitability of these distant worlds. A robust magnetic field is considered one of the essential criteria for a planet to be able to support life as we know it.

Models for Planetary Evolution Need Revising

Planetary scientists will need to revise their models of the thermal evolution of rocky planets. Until now, core cooling was modeled as a relatively simple process of heat loss and gradual solidification. The superionic state introduces an additional layer of complexity. The mobility of light elements affects not only the core’s mechanical properties but also its thermal properties. The diffusion of these atoms transports energy, alters temperature gradients, and can influence the rate at which the inner core solidifies. All these factors must now be incorporated into numerical simulations that predict planetary evolution over billions of years.

Professor Zhang and his team are already planning the next steps in their research. Other light elements are present in the Earth’s core—oxygen, sulfur, hydrogen, and silicon. Each could exhibit different superionic behavior, creating a complex mix of properties at the heart of our planet. Understanding how these different elements interact under the extreme conditions of the core is the next challenge. “We’re only just getting started,” acknowledges Dr. Huang. “The Earth’s inner core is a natural laboratory for states of matter that we’re only just beginning to explore.”

There is something humbling about this discovery. We think of ourselves as so advanced, so knowledgeable, with our technologies and theories. And yet, the core of the planet we’ve inhabited for hundreds of thousands of years held a fundamental secret. A secret that has just been uncovered—not through a sophisticated observation of deep space, but by a projectile launched at full speed against a piece of metal. Sometimes, to understand the infinitely large, you have to strike the infinitely small very hard.

What This Discovery Means for Science

The experimental confirmation of the superionic state under conditions found in the Earth’s core represents a major breakthrough for several disciplines. First, high-pressure physics, which now has a new category of states of matter to explore. Next, geophysics, which can finally explain decades of paradoxical seismic observations. Planetary science, which must revise its models of the evolution of rocky bodies. And even fundamental physics, which finds in the Earth’s core a natural laboratory for studying the behavior of matter under conditions that are impossible to sustain over the long term in a laboratory.

The practical implications may be more distant, but they do exist. Understanding how the Earth’s magnetic field is generated and maintained is crucial for predicting its future evolution. This field is not constant—it fluctuates, its poles shift, and it has even reversed hundreds of times throughout geological history. Predicting these changes is important for navigation, telecommunications, and protecting our electrical infrastructure from solar storms. If the superionic state plays a role in the dynamics of the geodynamo, understanding that role could improve our models for predicting the future behavior of the magnetic field.

A Fresh Perspective on Our Planet

Beyond the scientific and practical implications, this discovery invites us to look at our planet with fresh eyes. The Earth is not an inert block of rock on which we live. It is a dynamic, complex system where extraordinary processes are taking place at every moment—including 5,000 kilometers beneath our feet. The core of our world is a place where matter exists in states we cannot sustainably reproduce, where atoms dance freely through crystal lattices, where temperatures hotter than the Sun’s surface coexist with pressures capable of crushing any known material. And all of this helps maintain the invisible shield that protects us and makes life possible.

Perhaps this perspective should inspire us to be more humble. We tend to take the Earth for granted, as a stable backdrop for our human activities. But our planet is a living system, in the physical sense of the term—a system where flows of energy and matter continually interact to create the conditions we know. The superionic core is just one example of this complexity. Other discoveries will certainly follow, revealing further unsuspected aspects of our world. And each time, we will be reminded that the frontier of knowledge lies not only in distant stars—it also lies beneath our feet.

A discovery that resonates beyond the laboratories

Professor Youjun Zhang, Dr. Yuqian Huang, and their team at Sichuan University did more than simply answer a decades-old scientific question. They opened the door to a new understanding of what it means to live on a rocky planet. The Earth’s inner core is not the frozen ball of iron that textbooks described. It is a dynamic system, where carbon atoms circulate freely through a crystalline lattice of iron, creating a unique state of matter—superionic, “buttery,” neither truly solid nor truly liquid. This discovery explains decades of paradoxical seismic observations, reveals a new source of energy for Earth’s geodynamo, and opens up exciting prospects for understanding other worlds.

The shock compression experiments that led to this breakthrough are remarkable in their own right—projectiles launched at 7 km/s, pressures of 140 gigapascals, and temperatures of 2,600 Kelvin. Reproducing in the laboratory, even for just a fraction of a second, the conditions that prevail at the center of our planet represents a considerable technical feat. But beyond the technical feat, it is the result that matters: we now understand a little better how our Earth works, how it maintains the magnetic field that protects us, and why it has remained habitable for billions of years.

I end these lines with a strange feeling. A sense of wonder, certainly—how could one not be fascinated by a “buttery” planetary core? But also a sense of gratitude. Gratitude toward these researchers who are pushing the boundaries of our knowledge. Gratitude toward this extraordinary planet that shelters and protects us. And perhaps a little humility as well. We live on a ball of rock whose core is made of a material that defies our categories. A material that makes our existence possible. The next time you set foot on the ground, think about it. 5,000 kilometers beneath you, carbon atoms dance in an ocean of solid iron. And this dance—silent and invisible—maintains the shield that allows life to thrive. Perhaps that is the true miracle.

Unanswered Questions

Like any great scientific discovery, this one raises as many questions as it answers. Other light elements are present in the core—oxygen, sulfur, hydrogen, silicon. How do they behave under the extreme conditions at the center of the Earth? Do they also exhibit superionic behavior? How do they interact with each other and with iron? These questions will guide research in the coming years. And beyond Earth, what about other planets? Do the super-Earths discovered orbiting other stars have even more exotic cores? Could the superionic state explain certain mysterious magnetic properties of Mercury or Ganymede?

This is how science progresses—each answer gives rise to new questions, and every frontier pushed back reveals new territories to explore. Earth’s “buttery” core is just one chapter in a much broader story. The story of our understanding of the world we inhabit, the worlds we observe, and the states of matter that the universe can create. A story that has only just begun.

Editorial Stance

I am not a journalist, but a columnist and analyst. My expertise lies in observing and analyzing scientific discoveries that transform our understanding of the world. My work consists of dissecting scientific publications, understanding their implications, contextualizing technical advances, and offering analytical perspectives on the transformations that are redefining our view of the universe.

I do not claim to possess the cold objectivity of traditional journalism, which is limited to factual reporting. I aim for analytical clarity, rigorous interpretation, and a deep understanding of the scientific issues that affect us all. My role is to make sense of the facts, place them within their historical and scientific context, and offer an accessible interpretation of events.

Methodology and Sources

This text respects the fundamental distinction between verified facts and interpretive analysis. The factual information presented comes exclusively from verifiable primary and secondary sources.

Primary sources: original publication in National Science Review, official press releases from Sichuan University, statements by the researchers involved (Prof. Youjun Zhang, Dr. Yuqian Huang, Prof. Yu He).

Secondary sources: internationally recognized popular science publications (ScienceDaily, Earth.com, SciTechDaily), French-language science news outlets (Trust My Science, Generation-NT).

Nature of the Analysis

The analyses, interpretations, and perspectives presented in the analytical sections of this article constitute a critical and contextual synthesis based on the available information and expert commentary cited in the sources consulted.

Any subsequent developments in the scientific landscape could, of course, alter the perspectives presented here. This article will be updated if significant new information is published.