Researchers have discovered a hybrid phase of water, known as plastic ice, for the first time, which forms under high temperatures and pressures. This phase exhibits properties of both solid ice and liquid water, making it more easily molded or deformed than typical crystalline ice due to its plasticity. While most of the ice on Earth’s surface consists of a hexagonal lattice resembling a honeycomb, plastic ice has a cubic lattice structure. This discovery can help scientists better understand the internal architecture and processes of other worlds in our solar system and beyond.
Ice VII is a polymorph that forms at pressures above 20,000 bars, with a dense cubic structure in which molecules are ordered similarly to those in a Rubik’s Cube. There are over 20 known ice phases, including ice IX discovered in 1996, although it does not have the ability to freeze entire oceans. Computer simulations over 15 years ago theorized the existence of plastic ice VII, where water molecules can rotate freely while occupying fixed positions. The recent study utilized a new tool to observe the motions of molecules under extreme pressures, confirming the existence of plastic ice VII at temperatures over 177°C and pressures of about 30,000 bars.
The observation of plastic ice VII may have implications for understanding the early formational stages of moons like Europa and Titan in our solar system. It is believed that these moons may have contained plastic ice VII before water escaped from their high-pressure interiors, leading to their current state as ocean worlds. This discovery could help researchers piece together the evolution of these icy moons and how they transformed into their current environments. Additionally, this strange ice may also be present on exoplanets, particularly in the bottom of giant oceans that are thousands of kilometers deep and potentially habitable.
In the new study, researchers were able to identify plastic ice VII by analyzing the movements of water molecules under extreme temperatures and pressures using a neutron beam. The water molecules in plastic ice VII are held in fixed positions but are able to rotate in place, similar to liquid water. However, an unexpected finding was that the water molecules did not rotate freely but instead swiveled in jerky motions, breaking their hydrogen bonds with neighboring molecules. Understanding how plastic ice VII interacts with salts in its lattice could provide insight into nutrient exchange in exoplanet oceans and potentially enhance our understanding of habitability on other worlds.
The presence of plastic ice VII in the oceans of alien planets could have significant implications for the habitability and internal processes of these worlds. Investigating the incorporation of salts into its lattice could help researchers determine the role of plastic ice VII in nutrient exchange between exoplanet seafloors and oceans above. This could have important implications for the presence of life on these exoplanets and contribute to our understanding of the potential habitability of distant worlds. Plastic ice VII offers a unique opportunity to study the strange and fascinating properties of water under extreme conditions and advance our knowledge of planetary formation and evolution.
