What is it about?
Deep inside the Earth, pressures are so high that materials behave in surprising ways. This study reveals one such surprising discovery: iron, one of Earth’s most common and important elements, changes its basic chemical behavior, from an electron donor (reductant) to an electron acceptor (oxidant). The team used large-scale computer simulations to study how iron interacts with many “p-block” elements, such as silicon, sulfur, phosphorus, and heavier elements like tellurium and iodine, under increasing pressure, and found that iron bonds far more strongly with many of these elements in the deep Earth than it does at the surface. Elements that normally show little affinity for iron can become strongly attracted to it under core conditions, meaning some elements previously assumed to stay in the crust or mantle could actually be drawn into the core at extreme pressures. However, the researchers also discovered that the elements most depleted from Earth’s rocky layers are not the ones that bind tightly with iron at high pressure, suggesting that these “missing” elements were likely lost to space early in Earth’s history due to their volatility rather than being hidden in the core. The study also identifies silicon as behaving unusually strongly with iron under core pressures, supporting the idea that silicon is a major component of Earth’s core and helps explain why the core is less dense than pure iron.
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Why is it important?
This work is unique because it reveals, for the first time, that iron actually changes its fundamental chemical behavior under the immense pressures of Earth’s deep interior—switching from giving away electrons to taking them. This redox reversal had never been recognized across such a wide range of elements, and the study is the first to systematically map how iron interacts with almost the entire p-block of the periodic table under core pressures. The use of massive, modern computational tools makes it possible to explore chemical behaviors that cannot yet be tested experimentally, offering a new window into conditions found thousands of kilometers below our feet. The findings challenge long-standing ideas about why certain elements are scarce in Earth’s crust and mantle, and they provide fresh evidence about which elements may actually reside in the core—especially the surprising strength of silicon–iron bonding. By uncovering these hidden chemical rules of the deep Earth, this study helps refine models of how the planet formed, why elements are distributed the way they are, and what the core is really made of, making the work timely and highly relevant to current debates in geochemistry and planetary science.
Perspectives
For me, the most exciting part of this work is that it reveals a hidden side of iron—the element that, in many ways, defines the structure and evolution of our planet. For decades, we have treated iron’s chemical behavior as something well understood, but this study shows that at the pressures of Earth’s deep interior, iron becomes almost like a different element altogether. Discovering that iron can reverse its redox role and pull electrons from other elements was not something I expected when we began this project. Seeing this pattern emerge so clearly and consistently across the p-block was both surprising and deeply satisfying. It felt like uncovering a new rulebook for deep-Earth chemistry—one that helps explain puzzles that have lingered for years, such as why certain elements are missing from the mantle or what makes up the core’s mysterious “light-element” component. Personally, I hope this work encourages others to rethink long-held assumptions about how elements behave under extreme conditions and inspires more exploration into the unseen chemical world that shapes our planet from the inside out.
Maosheng Miao
California State University Northridge
Read the Original
This page is a summary of: Pressure-induced redox reversal of iron and the distribution of elements in deep Earth, Proceedings of the National Academy of Sciences, November 2025, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2414911122.
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