A new form of ice hitherto thought impossible has been discovered in the laboratory: in fact, it has a density practically equal to that of liquid water, a characteristic never observed in the various known types of solid ice, which have lower or higher densities.
The discovery, published in the journal Science and led by University College London (UCL), therefore calls into question all current knowledge and theories on water and the form in which it is found in the universe: in fact, while on Earth this type of ice may not exist in nature, on the icy moons of planets like Jupiter and Saturn it could be much more prevalent.
"What I find extraordinary is that an element like ice, which we use every day and which is so widespread both on Earth and in the rest of the universe, still continues to reveal surprises, after hundreds of years of study," he told ANSA. Andrea Sella, Italian researcher at UCL and co-author of the study.
“Even ice considered 'normal' is actually very strange”, continues Sella: “there is no other solid material that can float on its liquid form and that can take on so many different structures”.
In fact, there is not only one frozen water: there are 20 types of ice with the typical crystalline structure (in which the atoms are arranged in an orderly manner) and 2 amorphous types, i.e. in which the atoms are arranged in a disorderly manner. .
Although almost all frozen water on Earth exists in the form of crystalline ice, amorphous ice is probably the most common form in the universe, such as comets.
Yet, neither type has densities similar to that of liquid water.
The researchers led by Alexander Rosu-Finsen, however, have shown that a type of amorphous ice with these characteristics can also exist, and that it could be the true solid state of liquid water, just like window glass is the solid form of dioxide of liquid silicon.
"Basically, it is as if we had managed to immobilize the liquid - says the Italian researcher - it is water in 'stop-motion'".
To obtain it, the authors of the study vigorously 'shaken' a container cooled to -200 degrees, containing ordinary ice and steel spheres: instead of ending up with ordinary ground ice, the researchers found that the process had produced a completely new, a very white powder, called medium-density amorphous ice (Mda).
“It is an ice that exists only at -200 degrees, therefore it is impossible to find it on Earth – explains Andrea Sella – but it could play an important role on other planets and their moons, where the tidal forces due to the strong gravitational attraction can have an also on the glaciers that cover its surface, causing friction movements capable of producing this type of ice".