Solid water or ice is like many other materials because it can form a variety of solids based on varying temperatures and pressure conditions, such as carbon-forming diamond or graphite. However, water is exceptional in this respect, as we know of at least 20 solid ice forms.
A team of researchers working at UNLV’s Nevada Extreme Conditions Lab developed a new method for measuring the properties of high-pressure water. The water sample was first squeezed between the tips of two opposite diamonds – freezing into several mixed ice crystals. The ice was then subjected to a laser heating technique which temporarily melted it before it quickly turned into a powdery collection of small crystals.
By gradually increasing the pressure and blowing it intermittently with a laser beam, the team found that the water ice was moving from the known cubic phase, Ice-VII, to the recently discovered intermediate and tetragonal phase, Ice-VIIT. settling into another known phase, the Ice-X.
Zach GrandeA UNLV doctoral student, led the work, which also showed that the transition to Ice-X, when water hardens aggressively, occurs at much lower pressures than previously thought.
While it is unlikely that we will find this new ice age on any surface of the earth, it is likely to be a common ingredient in the Earth’s mantle as well as on the large moons and water-rich planets outside our solar system.
The research team had sought to understand the behavior of high-pressure water that can occur within distant planets.
Grande and a physicist at UNLV Ashkan Salamat placed a water sample between the tips of two round cut diamonds known as diamond glass cells, a standard feature in the field of high pressure physics. Applying a small force to the diamonds allowed the researchers to recreate as much pressure as at the center of the earth.
By squeezing a sample of water between these diamonds, the researchers drove the oxygen and hydrogen atoms into a variety of arrangements, including the recently discovered arrangement, Ice-VIIt.
In addition to allowing scientists to observe a new phase of water ice, the team’s first laser heating technique of its kind also found that the transition to Ice-X took place at almost three times less pressure than previously thought. At 300,000 atmospheric pressure instead of a million. This transition has been highly debated in the Community for several decades.
“Zach’s work has shown that this change in ionic state occurs at much, much lower pressures than previously thought,” Salamat said. “It’s a missing piece and the most accurate measurements ever in the water under these conditions.”
The work also recalibrates our understanding of the composition of exoplanets, Salamat added. Scientists hypothesize that the Ice-VIIT phase of ice could be abundant in the shell and upper mantle of expected water-rich planets outside our solar system, meaning they could have the right conditions for life.
Source: The Nordic Page