Scientists Discovered an Inexplicable New Kind of Ice. It Gets Hot Enough to Melt Steel.

3 min readHere’s what you’ll learn when you read this story:A new study details a new form of exotic ice that’s extremely dense and warm that forms under immense pressures. Scientists based in France studied this new form of ice, known as hexagonal close-packed (hcp) ice, by using diamond anvils and the European Synchrotron Radiation Facility’s Extremely Bright Source. If this type of ice exists in the interiors of Ice Giant planets such as Uranus and Neptune, it would help explain these planets’ non-axisymmetric magnetic fields.If you thought you knew ice, think again. When we think of ice, we’re actually visualizing naturally occurring ice, or “Ice I,” but there are actually dozens of different types of ice formed from a variety of ingredients at different temperatures and pressures—all the way up to Ice XXII, discovered just this year. Now, a new study published in the journal Physical Review Letters reports the discovery of another new form of ice—and it could help explain a strange astrophysical phenomenon in the outer solar system.This particular ice, known tentatively as hexagonal close-packed (hcp) ice (and possibly the future holder of the title Ice XXIII), is a kind of superionic water ice, in which the oxygen atoms are locked in a crystalline lattice while the hydrogen atoms move freely and—crucially—carry an electrical charge. Superionic ice was theorized for decades before scientists experimentally confirmed it in 2019, when a team reported in the journal Nature that they’d created a superionic phase with a face-centered cubic (fcc) oxygen lattice, now known as Ice XVIII. That fcc arrangement set Ice XVIII apart from the body-centered cubic (bcc) lattices of ices VII, VIII, and X. The new ice reported in Physical Review Letters is a step beyond even fcc superionic ice—and, like many ices before it, it was discovered using immense pressures and temperatures.The team, led by Alexis Forestier of France’s Atomic Energy and Alternative Energies Commission (CEA) in Paris, used diamond-anvil cells to trap microscopic water samples between two diamond tips. According to ZME Science, they surrounded each sample with a laser-absorbing, boron-doped diamond layer, then probed it with x-ray beams at the European Synchrotron Radiation Facility in Grenoble, France. As the researchers cranked up heat and pressure, the expected fcc superionic state emerged—but as pressures climbed toward two million times that of Earth’s atmosphere at sea level, things began to change.The scientists performed two runs, with the first reaching 80 gigapascals (GPa) and the other reaching up to 230 GPa. During the first run, concentrations of bcc, fcc, and hcp ices could be seen at 1086 Kelvin (K), or 1495 degrees Fahrenheit, but the second run shows how hcp ice takes over as pressure and temperature climbs.“Further compression to 197 GPa and heating to 2250 K led to an enhancement of the hcp reflections relative to the fcc ones,” the authors write. “Finally, during the last heating cycle up to 2630 K and 219 GPa, the fcc peaks almost vanished and the hcp ice phase clearly dominates.”The discovery of this ice at these temperatures and pressures could have real-world—or rather ice-world—consequences. The outermost planets in our solar system, Uranus and Neptune, are known as ice giants because their interiors are dominated by water, ammonia, and methane—compounds that astronomers lump together as “ices,” even when they exist as searing-hot fluids rather than anything frozen. When Voyager 2, the only spacecraft ever to visit the ice giants, measured their magnetic fields, they proved to be strikingly non-axisymmetric—unlike Earth’s, which is closely aligned with its rotation axis. Astronomers have long suspected that a thin layer of conducting fluid—rather than the planet’s interior as a whole—generates those lopsided fields. Superionic ice is a leading candidate for what surrounds that layer, and finding hcp ice deeper down could change how researchers model it.“The present observation that an hcp form of superionic ice may exist deeper within the inner shell of ice giants could therefore have important implications for the stratification and dynamics of their superionic mantles,” the authors write. “Our findings should motivate further theoretical work on the physical properties of hcp ice—especially its mechanical plasticity and electrical conductivity.”Darren lives in Portland, has a cat, and writes/edits about sci-fi and how our world works. You can find his previous stuff at Gizmodo and Paste if you look hard enough.