Researchers at Lawrence Livermore National Lab in California have discovered a new form of ice that is thought to exist within the core of gas giant planets. A new study published in the journal Nature documents the first observed instance of so-called “superionic ice,” which was originally predicted 30 years ago. The ice maintains a solid lattice structure of oxygen atoms with energetic, liquid-like hydrogen ions moving within. While it could only be created on Earth under very specific lab conditions, scientists believe it would be stable under the extreme temperature and pressure conditions found in planets such as Uranus and Neptune.
Unlike traditional ice, superionic ice actually requires extremely hot temperatures, combined with intense pressure, to form. Using a technique known as shock compression, scientists created laboratory conditions that match those found on gas giants and successfully prompted water to become superionic. The researchers noted the ice melts at near 5000 Kelvin (K) under pressure levels two million times that of Earth’s atmosphere. “Our work provides experimental evidence for superionic ice and shows that these predictions were not due to artifacts in the simulations, but actually captured the extraordinary behavior of water at those conditions,” said lead author and physicist Marius Millot.
While the real-world creation of superionic ice is groundbreaking, so too are the simulations that informed the experiment. “Driven by the increase in computing resources available, I feel we have reached a turning point,” explained co-author and physicist Sebastien Hamel. “We are now at a stage where a large enough number of these simulations can be run to map out large parts of the phase diagram of materials under extreme conditions in sufficient detail to effectively support experimental efforts.” The experiment has major implications for planetary science, painting a picture of gas giant cores composed of a thin layer of fluid surrounded by a thick mantle of superionic ice. The findings are especially poignant as NASA prepares for a potential probe mission to Uranus and/or Neptune.
Images via S. Hamel/M. Millot/J.Wickboldt/LLNL/NIF