Scientists have created a new type of ice that matches the density and structure of water. This could open the door for studying the mysterious properties of water.
“It could be liquid water that has frozen over time,” says Martin Chaplin, an expert in water structure at London South Bank University. “It could be very important.”
This ice is called medium density amorphous ice. A team led by Alexander Rosu-Finsen at University College London (UCL) placed regular ice in a small container and shook a 1 cm wide stainless steel ball at a temperature of -200 °C to create the deformities. . Seen before. The ice looked like a white granular powder stuck to the metal spheres. The results of the survey are today chemistry1.
haphazard molecule
Normally, when water freezes, it crystallizes, and its molecules are arranged in the familiar hexagonal solid structure called ice. Ice is less dense than liquid, which is an unusual property for crystals. Depending on conditions such as pressure and freezing rate, water can also freeze in any of her 20 other regular arrangements. Amorphous ice is different. There is no such order. “A lot of molecules are bound together haphazardly,” says Chaplin.
Two types of amorphous ice were discovered in the 20th century. “Low density” amorphous ice is the result of water vapor freezing on very cold surfaces at temperatures below -150 °C. “Dense” amorphous ice is formed by compacting regular ice under high pressure at similar temperatures. Neither type is common on Earth, but both are abundant in space. “Comets are large masses of low-density amorphous ice,” says Christoph Salzmann, his UCL chemist and co-author of the new study.
To crush the crystallized ice, the team used a ball mill, a tool typically used to crush or mix materials in mineral processing. A small amount of ice was shaken about 20 times per second using a container with a metal ball inside. Salzman said the metal balls created a “shear force” on the ice, breaking it into a white powder.
By shining X-rays on the powder and measuring how it bounces off, a process called X-ray diffraction, the team was able to figure out its structure. The molecular density of ice is similar to that of liquid water, and no obvious ordered structure was found in the molecules. This means that the crystallinity has been “destroyed,” Salzman says. “You are looking at a very chaotic substance.”
The results are “quite convincing,” says Marius Milott, a physicist at Lawrence Livermore National Laboratory in California. “This is a great example of how much more we still have to understand about water.”
The results are consistent with a model created by a team of scientists from the University of Cambridge, UK, to predict what would happen if normal ice were broken up in this way. However, it was previously frozen as crystallized ice, so it is unclear whether the resulting powder really matches the properties of liquid water. Further work is needed to investigate it.
big meaning
If confirmed, the new form of ice could enable the study of water in ways previously impossible. “Liquid water is a strange substance,” says Chaplin. “We still don’t know as much about it as we’d like to know.” This is consistent with the amorphous ice variant known to The discovery of intermediate-density amorphous ice could challenge that idea.
“If medium-density amorphous ice is indeed connected to liquid water, it means the model is incorrect,” Salzman says. “This could open a new chapter in ice research.”
It also makes sense to understand other worlds. Some moons of the solar system have icy surfaces, such as Jupiter’s moon Europa and Saturn’s moon Enceladus. If two of his ice regions on such a moon were to rub against each other due to tidal forces, the same shearing process the researchers used would produce intermediate-density amorphous ice between them. There is a possibility.
The increased density can create cracks in the surface, crack the ice, and crack the Moon. “There will be a massive collapse of ice,” says Salzman. “It could have serious implications for the geophysics of the icy moon.”
This, in turn, could affect the potential habitability of oceans of liquid water beneath the ice surface of these moons. Is there an interface between liquid water and rock, where life could emerge,” says Milott. “Amorphous ice may have a role that we need to understand.”
This article is reproduced with permission and was first published on February 2, 2023.
