When the Europa Clipper mission arrives on Jupiter’s distant Moon, it will look to find sources of water that are speculated to be present under the surface in the form of ice. Ahead of its launch, scientists have discovered a new form of ice that could be present in these distant worlds.
Scientists studying the properties of water under high pressure have discovered a new phase dubbed Ice-VIIt, an intermediate, and tetragonal phase between cubic phase, Ice-VII, and Ice-X. They said that it is unlikely that they will find this unique phase anywhere on the surface of Earth, but it could be a common ingredient within the mantle of Earth as well as in large moons and water-rich planets outside of our solar system.
The study published in Physical Review B pioneered a new method for measuring the properties of water under high pressure. Led by researchers from the Department of Physics and Astronomy at the University of Nevada Las Vegas, the team squeezed the water sample between the tips of two opposite-facing diamonds—freezing into several jumbled ice crystals.
The university said that applying a little bit of force to the diamonds enabled the researchers to recreate pressures as high as those found at the center of the Earth.
The ice was then subjected to a laser-heating technique that temporarily melted it before it quickly formed into a powder-like collection of tiny crystals. “By incrementally raising the pressure, and periodically blasting it with the laser beam, the team observed the water ice make the transition from a known cubic phase, Ice-VII, to the newly discovered intermediate,” the team said in a statement.
By squeezing the water sample between these diamonds, scientists drove the oxygen and hydrogen atoms into a variety of different arrangements, including the newly discovered arrangement, Ice-VIIt. The research not only helped discover a new phase of ice, but it also showed that the transition to Ice-X occurred at pressures nearly three times lower than previously thought — at 300,000 atmospheres instead of 1 million.
Led by Zach Grande, a Ph.D. student at the University of Nevada Las Vegas, the study helps in understanding the behavior of high-pressure water that may be present in the interior of distant planets.
“Zach’s work has demonstrated that this transformation to an ionic state occurs at much, much lower pressures than ever thought before. It’s the missing piece, and the most precise measurements ever on the water at these conditions,” physicist Ashkan Salamat said.
The new study could help astronomers understand the composition of exoplanets. Researchers hypothesise that the Ice-VIIt phase of ice could exist in abundance in the crust and upper mantle of expected water-rich planets outside of our solar system, meaning they could have conditions habitable for life.