Water is crucial for life to flourish, which is why it’s something scientists look for on other planets first, but can we really be sure what water looks like in extraterrestrial environments? In a new study published in Communications Chemistry, US researchers subjected water to the kind of pressure it would experience on planets like Uranus or Neptune and found that its fundamental atomic structure changes in response. In short, water becomes less symmetrical and more deformed, atomically, which has implications for how it conducts and influences heat. magnetic fields and affects a planet’s density, all of which is important for telescope observations and interpretations. This type of transformation has been previously predicted in simulations, but this appears to be the first time scientists have been able to observe it in the laboratory. “Water beyond Earth-like conditions has more complex behavior than we had ever imagined,” says physicist Ashkan Salamat of the University of Nevada, Las Vegas. “It’s amazing how water can behave under pressure.” The researchers placed a small drop of water between two diamond tips to apply pressure, raising it to more than 222 gigapascals (GPa). That’s about 2.2 million times the pressure we feel walking on Earth. Part of the experiment setup. (UNLV/Josh Hawkins) X-ray diffraction was used to identify chemical changes in water on the smallest scales, based on how the X-rays scattered as they passed through the water. Normally, you would expect squashed atoms to become more symmetrical as they are packed into tighter arrangements, but that’s not what happened here. The crystalline structure of the ice became more twisted and stretched. This gives us an idea of what is happening elsewhere in the Universe, although it is worth keeping in mind that only the pressure matches conditions on other planets, not the temperature. “We can’t get into the crust or atmospheres of these planets because of the distance, but we have data from things like the Voyager program,” Salamat says. “We have an idea of their composition, as well as the internal pressure and temperature. And in laboratories like mine, we can mimic the chemistry and experiment with what might be happening inside these planets.” The experiments also tell us more about X-ice, one of more than 20 types of ice known to scientists. Here, the team pushed ice-X beyond its known limits, creating something that looks new, although more studies will be needed to know for sure. frameborder=”0″ enable=”accelerometer; autoplay; writing on clipboard; encrypted media; gyroscope; picture in picture; web-share” referrerpolicy=”strict-origin-when-cross-origin” enablefullscreen> Ice-X forms gradually over a wide range of pressures, changing to a highly symmetric structure at around 50 GPa, in terms of its oxygen and hydrogen atoms. Now scientists have a better idea of what the upper limit of ice-X might be. “This transition marks the beginning of a new regime of structural complexity in high-pressure H2O, which redefines the upper limit of ice-X stability,” the researchers write in their published paper. Studying distant planets involves a lot of educated guesswork and careful interpretation of what telescopes report, and this study can help. It gives us a solid read on what water on Neptune (for example) might really be like. If the structure of water is different, then the chemical reactions it causes could be too: there may be rock and metal compounds found nowhere on Earth. That information is not only useful when it comes to run models of life on other planets, but in knowing what to expect when we get there, if our probes and spacecraft are going to go deeper into the Solar System. “Understanding the mechanisms of our Solar System and our observable Universe is fundamental to the human knowledge effort,” says Salamat. “When we finally reach these worlds, what will we see? We are really the first pioneers to try to answer these questions in the laboratory.” The research was published in Communications Chemistry. This article was fact-checked by Rebecca Dyer and edited by Rebecca Dyer. While we are proud of our process, we are human. If you spot an error, please let us know.
