Researchers have created a new form of ice with a density very similar to that of water, according to a study published Thursday in Science. By shaking a jar of ice and metal balls at extremely cold temperatures, the team created a white powdery ice with different properties than any kind previously known.
The new ice has an amorphous structure—instead of its molecules forming a neat and ordered crystalline pattern, like ice you might make in your kitchen, its molecules are disorganized, like those of liquid water.
“It might be liquid water frozen in time,” Martin Chaplin, who studies water structure at London South Bank University and did not contribute to the paper, tells Nature News’ Jonathan O’Callaghan. “It could be very important.”
Because of its ubiquity on Earth, water might seem like an ordinary fluid. But it has some unusual properties. For example, as water cools, its density peaks at four degrees Celsius, and it becomes less dense as its temperature continues to drop, which is why ice cubes float in a glass of water. But that’s unusual—most liquids become more dense as they cool, per Science News’ Emily Conover.
The researchers didn’t set out to make a new kind of ice. In the study, they placed regular ice and steel balls in a jar and cooled them to minus 200 degrees Celsius, shaking the container at about 20 times per second—just out of pure curiosity.
“It was one of those Friday afternoon experiments where you just do it and see what happens,” Christoph Salzmann, a physical chemist at University College London and co-author of the paper, tells New Scientist’s Leah Crane. “Naively, you’d think nothing would happen, you’d just break the ice down into smaller bits. But to our great surprise, something did happen.”
The research team used a process called ball milling, vigorously shaking ordinary ice together with steel balls in a jar cooled to -200 degrees Centigrade. “We shook the ice like crazy and destroyed the crystal structure,” said lead author Dr Alexander Rosu-Finsen. 2/6 pic.twitter.com/4Dr2q9arKk— UCL News (@uclnews) February 3, 2023
A “shear force” from the metal balls turned the ice into a white powder, Salzmann tells Nature News. The team fired X-rays at the powder to assess how its molecules were arranged. As the X-rays scattered, the researchers found the ice had no organized structure at all. A computer simulation demonstrated how randomly sliding layers of ice could make the structure become amorphous, per Science News.
Under more unusual circumstances, scientists have created two other forms of amorphous ice. In the 1930s, researchers condensed water vapor on a metal surface chilled to minus 110 degrees Celsius, forming amorphous ice with a lower density than water, per a statement. Compressing regular ice at extremely cold temperatures created the first amorphous ice with a higher density than water in the 1980s.
But the new ice is different: It has a density of 1.06 grams per cubic centimeter, which is very similar to water’s 1 gram per cubic centimeter, according to Live Science’s Stephanie Pappas. The researchers call it medium-density amorphous ice, or MDA.
These properties make scientists think MDA could be a glass phase of water. Glasses are created when a molten liquid cools very quickly, before its molecules can neatly arrange themselves, per Inverse’s Rahul Rao. On long timescales, glass has liquid-like properties, according to New Scientist.
Other researchers aren’t convinced MDA is very similar to water’s liquid form. Thomas Loerting, a physical chemist at the University of Innsbruck in Austria who didn’t contribute to the paper, tells Science News he thinks the new ice is instead “closely related to very small, distorted ice crystals.”
More research will be needed to better understand how closely this ice resembles liquid water. The researchers think studying it could help us better understand the moons of other planets, which might have amorphous ice on their surfaces, per Nature News.
“The big question is, what is this stuff?” Salzmann says to New Scientist. “I’m confident that if we can figure out what this MDA is, then we will understand liquid water much better.”