Superionic ice—an exotic phase of water that exists simultaneously as a solid and a liquid with free-flying hydrogen atoms—has been successfully recreated in a laboratory setting. According to a recent study published in Physical Review Letters, physicists used synchrotron X-rays and diamond-anvil cells to subject ultrapure water to temperatures reaching 4,274 degrees Fahrenheit (2,357 degrees Celsius) and pressures up to two million times Earth’s normal atmospheric pressure at sea level.
How Physicists Recreated Deep-Planet Ice on Earth
Recreating the crushing environments found deep inside Uranus and Neptune requires pushing experimental physics to extreme limits. According to Paris-Saclay University physicist Alexis Forestier and his research team, exploring the phase diagram of water ice under intense pressure has driven leading-edge developments for a century. To achieve this, the team squirted ultrapure water into a diamond cell, squeezed the diamonds together, and blasted the sample with X-ray lasers across two experimental sessions.
As the team ramped up the heat and pressure, the water molecules underwent distinct transformations. Above roughly 2,780 degrees Fahrenheit (1,526 degrees Celsius) and 200 gigapascals, the crystal structure began to display predicted superionic behavior. Rather than remaining a standard crystalline solid, the ice shifted into a hexagonal close-packed geometry where oxygen atoms formed a rigid lattice while hydrogen atoms moved freely throughout the structure.
Did you know? Scientists have discovered 22 distinct types of water ice so far, with ice XXI added to the official catalog in 2025. Most of these exotic crystalline forms only exist under specialized laboratory conditions rather than in household freezers or nature.
Decoding the Secrets of Ice Giants Like Uranus and Neptune
Understanding how water behaves under extreme compression helps planetary scientists model the interiors of distant cosmic objects. According to the study’s accompanying Synopsis column, the experiment specifically targeted predictions regarding ice X. Researchers previously suggested this phase enters a superionic state that extends the stability of ice across high temperatures, making the phase directly relevant to the internal dynamics of ice giant planets.
While the lab results align closely with theoretical models of compressed noble gases and predicted crystal lattices, confirming that Uranus and Neptune actually contain this exact material remains a distant goal. The research team notes that proving the composition of planetary interiors will likely take decades of further scientific advancements. In the meantime, these empirical observations provide critical boundaries for theoretical models exploring ice plasticity and electrical conductivity.
Frequently Asked Questions
What is superionic ice?
Superionic ice is an unusual phase of water where oxygen atoms lock into a rigid crystal lattice while hydrogen atoms flow freely through the structure like a liquid.
Where does superionic ice naturally occur?
Scientists believe superionic ice exists deep inside ice giant planets such as Uranus and Neptune.
How was superionic ice created in the lab?
Physicists squeezed ultrapure water inside a diamond cell while applying high-powered X-ray lasers to reach temperatures over 4,000 degrees Fahrenheit and extreme pressures.
How many types of water ice exist?
Researchers have identified 22 distinct types of water ice, with most existing only under extreme laboratory pressures and temperatures.
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