Scientists Observe HCP Superionic Ice at 219 Gigapascals, Sharpening Uranus and Neptune Models
Updated
Updated · ZME Science · Sep 10
Scientists Observe HCP Superionic Ice at 219 Gigapascals, Sharpening Uranus and Neptune Models
3 articles · Updated · ZME Science · Sep 10
Summary
At 219 gigapascals and 2,630 kelvins, researchers saw a hexagonal close-packed superionic ice structure dominate water’s X-ray signal for the first clear time.
Diamond-anvil cells and laser heating pushed a 12-micrometer sample above 2,000°C, locking oxygen into a crystal lattice while hydrogen nuclei stayed mobile and conductive.
The shift from the better-known fcc form appeared gradual, with hcp increasingly taking over as pressure and temperature rose; mixed structures had been hinted above roughly 150 gigapascals in earlier work.
Near 1,700 kelvins, the hcp phase showed directional thermal expansion, suggesting hydrogen may move more easily along some paths than others and potentially altering heat and charge transport.
That matters for Uranus and Neptune, whose tilted, non-axisymmetric magnetic fields may arise from currents in a thin conducting layer where this overlooked ice phase could be stable.