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In research that provides insight on water's behaviour under severe temperatures, scientists used a gadget that could be characterised as a super-duper cocktail shaker to create a previously unknown kind of ice – one that may exist on our solar system's icy moons.
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The researchers used a technique known as ball milling to aggressively churn common ice with steel balls in a container frozen to -328 degrees Fahrenheit (minus-200 degrees Celsius). This produced "medium-density amorphous ice," or MDA, which appeared as a fine white powder.
Resembling a fine white powder, the ice – named medium-density amorphous ice – is inside the jar below, together with the cold steel balls and liquid nitrogen. 4/6 pic.twitter.com/BNxtG60EQF
— UCL News (@uclnews) February 3, 2023
Ordinary ice is crystalline in form, with water molecules organised in a regular pattern — two hydrogen atoms and one oxygen atom, or H2O. The water molecules in amorphous ice are disorganised, resembling a liquid.
"Ice is a kind of frozen water that contains H2O molecules. H2O is a highly versatile molecular building block that, depending on temperature and pressure, can form a wide range of structures "said Christoph Salzmann, a physical and materials chemistry professor at University College London and senior author of the study published this week in the journal Science.
"Under pressure, molecules pack more effectively, which is why there are so many distinct types of ice," Salzmann continued.
Entirely new type of ice made using extremely cold steel balls: A new type of ice called medium-density amorphous ice has the same density as liquid water, so studying it could help us understand water’s strange behaviour at low temperatures https://t.co/KpvwTcQKcU pic.twitter.com/t89OjU1MG7
— Troubled Minds: A Conspiracy Radio Show/Podcast (@TroubledMindsR) February 2, 2023
Almost all ice on Earth occurs in its classic crystalline form – consider the ice cubes in your lemonade. Amorphous ice, on the other hand, is by far the most abundant kind of water in space. Scientists have discovered 20 different types of crystalline ice, as well as three types of amorphous ice — one low density (discovered in the 1930s), one high density (discovered in the 1980s), and the new one in between.
Amorphous ice on Earth may be restricted to the freezing highest regions of the atmosphere.
"Almost all ice in the cosmos is amorphous, and it exists in the form of low-density amorphous ice," Salzmann explained. "This is formed when water in space condenses on dust grains. Comets are also made of amorphous ice. Liquid water necessitates extremely specific circumstances, such as those found on Earth. However, there is evidence of underground seas on several of the solar system's ice moons."
In industry, ball milling is used to grind or combine materials. The approach was employed by the researchers to create around 3 ounces (8 grammes) of fresh ice, with part of it kept in cold storage.
The question is whether this type of ice exists in nature. The researchers hypothesise that the forces they applied to conventional ice in the laboratory may exist on ice moons such as Jupiter's Europa or Saturn's Enceladus.
"For the first time, we created MDA ice. So the samples in our lab must be the only ones on the planet "Salzmann explained.
"We believe it may exist on some of the solar system's ice moons. As the ice crystals contact with the steel balls, shear forces are generated within them. Tidal forces from the gas giants (Jupiter and Saturn) are at work in the ice moons, and we expect them to create identical shear stresses in the moons' ice shells as during ball milling "Salzmann went on to say.
The study might lead to a better understanding of water, a molecule that is essential to life.
"The fact that this new form of ice has a density similar to that of liquid water — and thus may be a good model for understanding water without the motion of the liquid — is probably the most important aspect of this discovery," said Angelos Michaelides, a chemistry professor at the University of Cambridge and study co-author.
"Because MDA is likewise in a disordered condition like liquid water, the issue arises as to whether it is indeed liquid water but at low temperatures," Salzmann explained. "Building on this, MDA offers the possibility of ultimately understanding liquid water and its numerous peculiarities."
