The fact that ice floats on liquid water is part of our everyday experience. However, it is a phenomenon that, in a certain way, defies the laws by which other substances in nature behave. H2O has peculiar characteristics compared to other elements, and it is these properties that make it, the primordial element of life , responsible for ensuring the success of living creatures on Earth.
Aware of these peculiarities, and with the intention of studying in depth the characteristics of water at a temperature below 0 degrees, an international team of researchers has managed to keep the water liquid at -43 degrees Celsius. Although other experiments had previously observed this extraordinary capacity, the innovation of the study, published in the journal Physical Review Letters , lies in the technique used to measure its temperature.
The scientific team injected water droplets of about 6 microns in diameter, all of the same size, into a vacuum chamber , and to find out if they were still liquid they illuminated them with a focused laser beam. The further the droplets traveled through empty space, at a speed of 45 miles per hour, the more they cooled by surface evaporation.
“The key to obtaining the temperature of the droplets with great precision lies in analyzing the frequency or wavelength, which ‘bounces’ off the drop of water itself,” researcher José María Fernández, from the Institute of Structure, explained to Very Interesting. of the Matter and member of the Higher Council for Scientific Research (CSIC).
Thus, the team observed a correlation between these resonance modes and the size of the droplet, which, in turn, could relate it to temperature: the smaller the size, the lower the temperature.
“By analyzing the frequencies of the light that resonated in the droplets, we were able to measure the temperature of this water , with a precision of 0.6 degrees,” explains Fernández.
The peculiarities of water
Water has a series of anomalous properties, such as its density. Its solid form is less dense than the liquid, a characteristic that has allowed, for example, to preserve life at the bottom of frozen lakes during ice ages.
Furthermore, the fact that the melting of the polar caps does not modify the sea level has been decisive in regulating the planet’s climate. “If you put an ice cube in a glass of water and watch it melt, you will see that the water level remains constant in the glass,” exemplifies Fernández.
The origin of the peculiar properties of water, which has almost no other substance, lies in how its molecules behave or, more specifically, how they are linked to each other.
The secret is in the hydrogen bonds , forming a three-dimensional network between the hydrogen atoms. This explanation would be responsible for the anomalies that we have described previously, although a detailed molecular explanation does not yet exist.
Given the evidence that water is a substance that behaves in a unique way, and that it is essential for life, it is inevitable to wonder if liquid water could exist at temperatures never seen on Earth in other corners of the universe.
“It must be taken into account that the liquid water droplets at 43 degrees below zero in the experiment had a life of just a few milliseconds”, the researcher acknowledges. “It is not easy for water to exist in nature under these conditions, although liquid microdroplets have been detected at -35ºC in high clouds in the Earth’s atmosphere,” he says.
However, Fernández does recognize that under extraordinary states of pressure, water could behave in ways we did not expect. This leads us to think that, perhaps, the conditions may exist for liquid water to exist at extremely low temperatures, for example, under the ice of moons such as Europa or Enceladus, thus being able to host extraterrestrial life in its hypothetical oceans.
Claudia Goy, Marco AC Potenza, Sebastian Dedera, Marilena Tomut, Emmanuel Guillerm, Anton Kalinin, Kay-Obbe Voss, Alexander Schottelius, Nikolaos Petridis, Alexey Prosvetov, Guzmán Tejeda, José M. Fernández, Christina Trautmann, Frédéric Caupin, Ulrich Glasmacher, and Robert E. Grisenti. Shrinking of Rapidly Evaporating Water Microdroplets Reveals their Extreme Supercooling. Physical Review Letters. DOI: 10.1103 / PhysRevLett.120.015501