Scientists have discovered a new form of ice

(ORDO NEWS) — UNLV researchers have discovered a new form of ice that is redefining the properties of water at high pressure.

Solid water or ice, like many other materials, can form various solid materials depending on conditions of varying temperature and pressure, such as carbon forming diamond or graphite.

However, water is exceptional in this aspect, since we know of at least 20 solid forms of ice. A team of scientists working at UNLV’s Extreme Conditions Laboratory in Nevada has developed a new method for measuring the properties of high-pressure water.

The water sample was first compressed between the tips of two diamonds facing each other and frozen into several intermixed ice crystals. The ice was then subjected to laser heating, which temporarily melted it before it quickly turned into a powdery array of tiny crystals.

By gradually increasing the pressure and periodically shooting it with a laser beam, the team watched as the water ice made the transition from the known cubic phase, Ice-VII, to the newly discovered intermediate and tetragonal phase, Ice-VIIt, before moving into another known phase, Ice-X .

Zach Grande, UNLV Ph.D. student, led the work, which also demonstrated that the transition to Ice-X, when the water hardens aggressively, occurs at a much lower pressure than previously thought.

While it’s unlikely we’ll find this new phase of ice anywhere on Earth‘s surface, it’s most likely a common component of Earth’s mantle, as well as large moons and water-rich planets outside our solar system.

The group’s findings were published in the March 17 issue of Physical Review B. The research team has been working to understand the behavior of high-pressure water that may be present in the interior of distant planets.

To do this, Grande and UNLV physicist Ashkan Salamat placed a water sample between the tips of two round-cut diamonds known as diamond anvil cells, a standard feature in high pressure physics. Applying a small amount of force to the diamonds allowed the researchers to recreate a pressure as high as at the center of the Earth.

By placing a sample of water between these diamonds, the scientists brought the oxygen and hydrogen atoms into various locations, including the newly discovered Ice-VIIt location.

Not only did the first-of-its-kind laser heating method allow scientists to observe a new phase of water ice, the team also found that the transition to Ice-X occurred at a pressure almost three times lower than previously thought – at 300,000 atmospheres instead of 1 million atmospheres. This transition has been a widely discussed topic in the community for several decades.

“Zak’s work demonstrated that this conversion to an ionic state occurs at much lower pressures than has ever been thought,” Salamat said.

“This is the missing piece and the most accurate measurement ever taken on the water in these conditions.”

The work also redefines our understanding of exoplanet composition, Salamat added. The researchers speculate that the Ice-VIIt ice phase may exist in abundance in the crust and upper mantle of putative water-rich planets outside our solar system, meaning that they could have conditions for life.


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