Superionic hcp ice mimics ice‑giant interiors

Laboratory experiments have produced a hexagonal close‑packed (hcp) crystal form of water and observed it enter a superionic state when squeezed to ~230 GPa and heated to thousands of kelvins. These conditions reproduce regimes expected inside Uranus‑ and Neptune‑like planets and validate theoretical predictions about water’s behaviour at extreme pressures. — This matters because direct experimental evidence of water’s phase behavior under ice‑giant interior conditions constrains planetary interior models, informs explanations for unusual planetary magnetic fields, and advances materials physics under extreme conditions.