Scientists Uncover Strange New State of Matter Inside Uranus and Neptune

Deep within the distant ice giants of our Solar System, familiar elements may behave in unfamiliar ways.

The deep interiors of ice giants such as Uranus and Neptune may contain a previously unknown form of matter, based on new computational research by Carnegie scientists Cong Liu and Ronald Cohen.

Their study, published in Nature Communications, suggests that carbon hydride can form a quasi-one-dimensional superionic state under the extreme pressures and temperatures found far beneath the surfaces of these distant planets.

More than 6,000 exoplanets have now been identified, and that number continues to rise. To better understand these worlds, researchers from astronomy, planetary science, and Earth science are increasingly working together. By combining observations, experiments, and theoretical models, they aim to uncover the processes that shape planets, including how magnetic fields form.

This growing effort has also increased interest in what happens deep inside planets and moons in our own Solar System. Studying these hidden regions can improve our understanding of planetary behavior and may even provide clues about habitability beyond Earth.

The Mystery of “Hot Ices”

Data on Uranus and Neptune show that their interiors likely contain layers of unusual “hot ices.” These layers sit between the outer hydrogen and helium atmospheres and the inner rocky cores. Scientists believe they are made up of water (H2O), methane (CH4), and ammonia (NH4), but under such extreme conditions, these materials may take on unfamiliar forms.

At very high pressures and temperatures, matter can behave in unexpected ways. This is why scientists use both experiments and theoretical models to explore what might exist inside these planets.

To investigate this, Liu and Cohen used advanced computing and machine learning to run quantum-level simulations of carbon hydride (CH). They examined conditions ranging from about 5 million to 30 million times Earth’s atmospheric pressure (500 to 3,000 gigapascals) and temperatures between 6,740 and 10,340 degrees Fahrenheit (4,000 to 6,000 Kelvin) (about 12,000 to 18,600 degrees Fahrenheit).

Their results point to the formation of a structured hexagonal lattice, where hydrogen atoms travel along spiral-like paths. This motion creates a quasi-one-dimensional superionic state.

Superionic materials fall between solids and liquids. In these systems, one set of atoms stays locked in a crystal structure while another set moves freely through it.

“This newly predicted carbon–hydrogen phase is particularly striking because the atomic motion is not fully three-dimensional,” Cohen explained. “Instead, hydrogen moves preferentially along well-defined helical pathways embedded within an ordered carbon structure.”

Implications for Planetary Science

The directional movement of hydrogen in this material could affect how heat and electricity flow inside planets. This, in turn, may influence how energy is distributed, how well these regions conduct electricity, and how scientists interpret the magnetic fields of ice giants.

The study also shows that even simple chemical systems can develop complex structures under extreme conditions, expanding what researchers know about matter at high pressure and temperature.

“Carbon and hydrogen are among the most abundant elements in planetary materials, yet their combined behavior at giant-planet conditions remains far from fully understood,” Liu concluded.

Beyond planetary science, discovering materials with strongly directional properties could also be useful in materials science and engineering, where such behavior might lead to new technologies.

Reference: “Prediction of thermally driven quasi-1D superionic states in carbon hydride under giant planetary conditions” by Cong Liu, R. E. Cohen and Jian Sun, 16 March 2026, Nature Communications.
DOI: 10.1038/s41467-026-70603-z

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