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| Ice XXI: a new crystalline phase revealed by high-pressure X-ray experiments. |
Lead: In a surprising breakthrough, researchers have identified a brand new phase of ice — called Ice XXI — created by squeezing water to ultrahigh pressures while observing the sample with ultrafast X-ray flashes. This discovery expands our understanding of water’s many possible crystalline forms and has implications for planetary science and high-pressure physics.
How did scientists create Ice XXI?
Using a dynamic diamond anvil cell (dDAC) to supercompress tiny volumes of water to pressures above about 2 gigapascals, and probing the sample on microsecond timescales with an X-ray free-electron laser, researchers were able to trap and image a previously unknown crystallization pathway that produces Ice XXI. The experiment combined advanced high-pressure hardware with the European XFEL’s ultrashort X-ray pulses to see the structural transition in real time.
Why is Ice XXI surprising?
We’re used to thinking of ice as a simple solid formed when water cools below 0°C. But condensed-matter physics has shown there are many crystalline and non-crystalline forms of water under extreme conditions. Ice XXI forms at room temperature when water is rapidly pressurized — a pathway that traditional textbooks don’t illustrate. The new phase is metastable and appears only under those specific supercompression conditions, revealing hidden complexity in how hydrogen bonds reorganize under stress.
What does this mean for planetary science?
Planets and moons with massive ice layers — such as some of Jupiter and Saturn’s moons, or ice-rich exoplanets — expose water to enormous pressures in their interiors. Discovering Ice XXI on Earth in the lab helps scientists refine models of how ice behaves inside those worlds. In other words, each new ice phase can change our picture of internal structure, heat transport, and even how magnetic fields or subsurface oceans form on icy bodies.
Technical details — a quick primer
- Pressure used: > 2 GPa (more than 20,000 atmospheres).
- Tools: dynamic diamond anvil cell (dDAC), European XFEL X-ray pulses, time-resolved diffraction and simulation.
- Timescale: microseconds — the team captured freezing-melting cycles extremely rapidly to see the crystallization pathway.
How reliable is the discovery?
The work was published in a peer-reviewed journal and reported by high-quality outlets; the combination of experimental imaging and computational modeling helps confirm the structural assignment. As always, independent follow-up experiments and computational confirmations will strengthen and refine the picture, but the evidence to date is robust and widely covered by science media.
Why you should care — quick takeaways
- Even simple molecules like water can hide complex behaviors under extreme conditions.
- Ice XXI helps us rethink models of icy planets and moons — and suggests more undiscovered phases may await.
- High-pressure, ultrafast experiments are opening windows into transient states of matter previously inaccessible to science.
Explore related posts on SpDt
For more on space and planetary science, see our Science collection: Science on SpDt. Also check earlier posts on solar and space events for context on how we study planetary phenomena.
Watch the short video
We made a concise video explaining Ice XXI and what it means for planetary science. Watch it on our YouTube channel and subscribe to the SPDT Channel for more science shorts.
