Scientists discover a weird and previously unknown form of ice
Scientists from Cambridge and University College London (UCL) have created a new form of ice which is amorphous in nature. The new ice had a density similar to liquid water while its state resembled water in solid form. As opposed to ordinary crystalline ice, where molecules have a regular pattern, in amorphous ice, the molecules are in a disorganized form-like a liquid.
Why does this story matter?
- Amorphous ice is the main type of ice found in space but it is rarely found on Earth. This is because, in the colder environment of space, ice does not have enough thermal energy to form crystals.
- What's fascinating about this study is that this kind of ice might be what is found on distant moons in the solar system.
The ball milling technique was used for creating new ice
The new ice was created using a method called ball milling, which is normally used to grind or blend materials in mineral processing. Ball-milling is regularly used to make amorphous materials but has never been applied to ice, according to the team. Researchers shook regular ice in a small container with centimeter-wide stainless-steel balls at temperatures of -200 degrees Celsius to produce the variant.
The new ice is called medium-density amorphous ice
The metal balls produced a 'shear force' on the ice, breaking it down into a white granular powder, that remained stuck to the metal balls. The novel amorphous form of ice, resulting from the process, was called medium-density amorphous (MDA) ice. It has a density of 1.06 grams per cubic centimeter, close to the density of water which is 1 gram per cubic centimeter.
"Two main types of amorphous ice have previously been discovered"
"We know of 20 crystalline forms of ice, but only two main types of amorphous ice have previously been discovered, known as high-density and low-density amorphous ices," said Christoph Salzmann, a chemist from UCL and senior author of the study. "There is a huge density gap between them and the accepted wisdom has been that no ice exists within that density gap."
"The density of MDA is precisely within this density gap"
"Our study shows that the density of MDA is precisely within this density gap and this finding may have far-reaching consequences for our understanding of liquid water and its many anomalies," added Salzmann.
MDA could exist on icy moons like Europa and Enceladus
The team suggested that MDA may exist inside icy moons of the outer solar system, such as Jupiter's moon Europa and Saturn's moon Enceladus. If two icy areas on the moons were to rub together because of tidal forces from these planets, they could produce MDA ice between them, similar to the shearing process that the researchers used.
MDA could trigger tectonic motions on moons such as Ganymede
Further, the team used calorimetry to investigate the heat released when MDA was recrystallized at warmer temperatures. They found that when MDA was warmed up and recrystallized, it released an "extraordinary amount of heat." This suggests that it could trigger tectonic motions and "icequakes" on ice-encrusted moons such as Jupiter's Ganymede. Broadly speaking, this discovery shows water can be a high-energy geophysical material.
"This is an unexpected and quite amazing finding"
"We have shown it is possible to create what looks like a stop-motion kind of water," said Andrea Sella, a chemist from UCL. "This is an unexpected and quite amazing finding."