Photo: sciencealert
An international team of researchers has created an entirely new form of ice that remains solid at room temperature. The newly discovered phase, called Ice XXI, was produced by compressing water between two diamonds under extreme pressure, according to LiveScience.
Ice XXI forms when water molecules are subjected to immense pressure — roughly 20,000 times higher than Earth’s atmospheric pressure. Under these conditions, water enters a metastable state — a temporary, delicate phase that can become unstable with even the slightest disturbance. During the experiment, published in Nature Materials, scientists observed how water’s structure shifted from high-density to very high-density ice.
To detect this new ice phase, the team used the European X-ray Free Electron Laser (XFEL) — the world’s most powerful X-ray laser. This allowed researchers to monitor structural changes in real time, capturing snapshots every millionth of a second.
“Thanks to XFEL’s unique X-ray pulses, we tracked multiple crystallization pathways as we repeatedly compressed and released water over a thousand times in a dynamic diamond anvil cell,” explained co-author Kin Woo Lee of the Korea Research Institute of Standards and Science (KRISS).
The breakthrough was made possible by using a diamond anvil cell — a device that generates extreme pressures using ultra-hard diamonds. Under such intense conditions, H₂O molecules are forced so close together that they form a new, dense crystalline structure.
“Our results suggest that more high-temperature metastable phases of ice may exist than previously thought,” said co-author Rachel Husband from the Deutsches Elektronen-Synchrotron research center. “This opens up new possibilities for understanding the composition of icy moons and planets.”
Ice XXI becomes the 21st known phase of ice, joining previously discovered forms such as tetragonal Ice XIX and the superionic “hot star” ice found in earlier experiments. Water is a uniquely versatile substance, capable of existing in dozens of solid states — from crystalline to amorphous — due to the flexible arrangement of hydrogen atoms in its structure.
While earlier experiments focused on ice formation at low temperatures, this study demonstrated that even at room temperature (around 22°C), water can freeze into a solid form under extreme pressure. The finding could help explain the presence of exotic crystalline water structures on distant planets and moons.
In a related discovery, astronomers recently confirmed the presence of heavy water (H₂O containing deuterium) in a protoplanetary disk around the young star V883 Orionis using the ALMA telescope. The observed ratio of heavy to regular water matches that of water older than the Solar System — providing the first direct evidence that water can survive the birth of stars and planets.
