A team of researchers has published a paper in Science describing a novel form of ice known as amorphous ice. Unlike conventional crystalline ice, where the molecules are arranged in a predictable pattern, the molecules in amorphous ice are disordered and have a liquid-like appearance.
The team created a new form of ice through an experimental process called ball-milling, which involved grinding crystalline ice into small particles using metal balls. This method is commonly used to create amorphous materials but has never been tried with ice. The team also developed an atomic-scale model of the new form of ice through computer simulation.
Medium-Density Amorphous Ice
The researchers discovered that the ball-milling process resulted in the creation of a new type of ice called medium-density amorphous ice (MDA), which has a density similar to liquid water and a state that resembles solid water. The team used computational simulation better to understand the molecular process at the molecular level. They mimicked the ball-milling process through repeated random shearing of crystalline ice, resulting in a successful computational model of MDA.
Dr. Michael Davies, who was involved in computational modelling, emphasized the significance of understanding the precise atomic structure of MDA. He noted that the discovery of MDA raised numerous questions about the nature of liquid water and pointed out the remarkable similarities between MDA and liquid water.
Previously, there were two main types of amorphous ice: high-density and low-density amorphous ice. The significant density difference between the two has been a key aspect in understanding the nature of liquid water, leading to the theory that water consists of two separate liquids with different densities. The discovery of medium-density amorphous ice (MDA) has added another piece to the puzzle, as the density of MDA is closer to that of liquid water. According to Senior author Professor Christoph Salzmann, conventional wisdom held that there was no ice within the density gap.
Part of the set-up for creating medium-density amorphous ice: ordinary ice and steel balls in a jar (not amorphous ice)
Liquid Water Similarities and Peculiarities
However, their study found that the density of MDA falls within this gap, and this discovery could have significant implications for our understanding of liquid water and its peculiarities. The discovery of MDA raises the following inquiry: Where in nature might it be found? In this study, shear forces were essential for forming MDA. The team suggests that the tidal forces that gas giants like Jupiter exert could cause ordinary ice to experience similar shear forces in the icy moons.
In addition, MDA possesses a remarkable quality that is absent in other types of ice. They discovered via calorimetry that MDA recrystallizes ordinary ice and emits an extraordinary amount of heat. The heat released during MDA recrystallization may influence tectonic motions' activation.
In general, this finding demonstrates that water can function as a high-energy geophysical material. The Cambridge lead writer, Prof. Angelos Michaelides, noted that amorphous ice is considered a standard type of water in the universe. As reported by Science Daily, the race to resolve how much of it is MDA, and how geophysically active it is will just be underway.
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