According to New Atlas, water takes many more forms than many thought, and now scientists have recreated a particularly bizarre form in the lab — a kind of "hot black ice" that may exist deep in planets like Uranus and Neptune.
This stage of water is called "superionic ice", which forms at extremely high temperatures and pressures, causing water molecules to separate into hydrogen and oxygen ions that are composed of them. The oxygen ions then line up into a cubic lattice, and the hydrogen ions move freely around it. Taken together, this gives superionic ice a relatively high conductivity and low density, and a darker color.
Still, actually studying this kind of stuff has been tricky. This phase has been theorized for decades, and experimental evidence began to emerge in the 1990s, but it wasn't until 2019 that scientists managed to produce superionic ice in the lab. In that experiment, however, it lasted only a moment.
Now, scientists at Argonne National Laboratory in the United States have successfully created stable superionic ice that lasts long enough for more detailed studies. First, pressure is applied by squeezing a sample of water in a diamond anvil trough, and then the water is heated with a laser. Finally, a powerful X-ray laser called an advanced photonic source (aps) was used to image the arrangement of atoms in the sample to figure out what stage the water was at.
Sure enough, the study showed that the experiment was producing superionic ice. It begins to appear at temperatures between 627 °C and 1627 °C, as well as under pressure of 20 gigapascal. Intriguingly, this is much less stressful than the model predicts for the formation of this phase.
Study co-author Vitali Prakapenka said: "It's a surprise – everyone thinks this stage won't come up until you're under a lot more stress than where we first discovered it. But we were able to map the properties of this new ice very accurately, which constitutes a new phase of matter, thanks to several powerful tools. ”
Studying the superionic ice produced in the lab could help scientists understand how planets formed and even inform the search for extraterrestrial life. It is thought that this ice will be found on icy giants such as Uranus and Neptune. The team says more work needs to be done to explore what makes superionic ice work. Its properties such as electrical conductivity, viscosity, and stability are still obscure, and things can change dramatically when it is mixed with salts or other minerals.
The study was published in the journal Nature-Physics.