Water isn't always as it seems. Under extreme conditions, such as those found on other planets, it has been discovered to change its atomic structure, giving it the means to alter its appearance and other properties.
A new UNLV study published in Communications Chemistry, a Nature Portfolio journal, shows that as pressure is applied to water, it becomes a lower-symmetry version of its previous self.
"Water beyond Earth-like conditions has more complex behavior than we ever previously imagined," said UNLV physicist Ashkan Salamat, research lead and director of the university's Nevada Extreme Conditions Lab. "It's amazing how water can behave under pressure."
Typically as you compress materials, you reduce the volume and force atoms to get closer and closer to each other. The norm and expectation is that this would create higher-symmetry arrangements of the atoms, but water has demonstrated that this is not the case. And as you squeeze it, its chemistry changes.
Salamat's lab put water under the equivalent of 35 million pounds per square inch (PSI). For reference, a car tire is about 30 PSI. In doing so, the lab replicated conditions closer to those found on Neptune or Uranus. These so-called ice giants are really balls of molten, metallic-like water, ammonia, and methane.
"We can't enter the crust or atmospheres of these planets because of distance, but we have data from things like the Voyager program," said Salamat. "We have an idea of their compositions, and interior pressure and temperatures. And in labs like mine, we can mimic the chemistry and experiment with what could be occurring inside these planets."
The findings of the research tell us that water can take unfamiliar forms. Water could very well be a shapeshifter of sorts, and exist in a very different structural appearance than here on Earth due to much higher levels of pressure. If the pressure were to release, the cosmic water would likely rearrange itself into a known structure more commonly found on our planet.
This was tested using spectroscopy, squeezing samples between two diamonds (the hardest known material) to create extraordinary pressures. Then, X-rays were used to look at the structural arrangement of the atoms.
"Understanding the mechanisms of our solar system and our observable universe is critical for the endeavor of human knowledge," he said. "When we eventually get to these worlds, what are we going to see? We're really the initial pioneers in trying to answer these questions in the laboratory."