It's amazing how water can behave under pressure,
researchers noted in a study published October 15 in the journal Communications Chemistry. The findings reveal that solid water becomes less orderly under extreme force, contradicting long-held scientific expectations that atoms would settle into more symmetrical patterns when compressed.
Crushing water with 2.2 million atmospheres of force
To witness this transformation, scientists applied pressure up to 35 million pounds per square inch—or 222 GPa. This force is roughly 2.2 million times the pressure felt on Earth. Using X-ray diffraction at Argonne National Laboratory’s Advanced Photon Source and the Advanced Light Source, the team monitored how atoms responded by measuring how X-rays scattered through the compressed substance.
The study focused on ice-X, a high-pressure form of ice that typically forms gradually across a broad range of pressures. While ice-X usually shifts into a highly symmetrical structure at around 50 GPa, the researchers observed it losing that orderly, cube-like pattern. Instead, the crystal structure became a lower-symmetry version of itself.
Water behavior reveals secrets of ice giants
The molecular behavior of water carries heavy implications for planetary science, specifically for Uranus and Neptune. Classified as “ice giants,” these planets consist of hot, dense mixtures of water, ammonia, and methane. Because atomic arrangement dictates density, electrical and heat conductivity, and the generation of magnetic fields, understanding these shifts is critical to interpreting data from the distant planets.
The researchers noted that if the pressure were released, the water would likely return to a familiar form, similar to ice found on Earth.
The hunt for the exact atomic arrangement
While the data indicates a shift in structural complexity, identifying the precise new atomic arrangement remains an ongoing challenge. Computer models favor one candidate structure, but the experimental data could also fit a second one. The authors emphasize that more experiments are required to determine which arrangement is correct and whether these changes influence how water reacts with other materials.