Both Uranus and Neptune are believed to have “superionic” water ice, a peculiar form of the substance that is a mix of solid and liquid properties. While this has yet to be definitively proven, a team of scientists has come up with their own version of this ice, adding to the surprisingly complex nature of water, despite its simple chemical composition.
With two hydrogen atoms and one oxygen atom, water is one of the simplest molecules known to man, the New York Times wrote. These atoms are arranged in a looser V-shaped setup in liquid water, but when it comes to ice, they connect to each other in a crystal lattice structure that has more space in between atoms. This explains water’s peculiar tendency to expand once frozen, which sets it apart from most other substances.
All in all, there are close to 20 different types of ice based on the arrangement of the water molecules — the Smithsonian wrote that these include cubic and hexagonal configurations, among others. Superionic ice can now be counted among those many types discovered by researchers, and the new discovery comes about three decades after scientists originally posited that the substance might be found underneath high-pressure environments with hot temperatures.
While it might sound unusual for water ice to be found in such circumstances, the heat and high pressure are thought to work together to make the phenomenon work, with the heat melting the bonds that connect hydrogen and oxygen atoms, and the pressure ensuring that the oxygen atoms retain their crystal lattice-like structure. This allows positively charged hydrogen ions to pass through smoothly and act as a conductor of electricity in lieu of the usual negatively charged ions.
In a study published Monday in the journal Nature Physics, researchers described the processes they used in creating superionic water. The researchers conducted the experiments at the Lawrence Livermore National Laboratory in California, compressing water between two diamonds, and squeezing the water through ice VII, a form of solid ice that’s approximately 60 percent denser than water in its usual form. The water was subjected to 360,000 pounds per square inch of pressure, or about 25,000 times the pressure we typically experience when air presses against us. The compressed ice was then sent on a coast-to-coast trip to the University of Rochester in New York, where scientists then used laser light to send shock waves through the ice.
In a series of laser blasts that took only 10 to 20 billionths of a second each, the researchers were able to exert even more intense pressure — over a million times more than what’s considered normal on Earth’s atmosphere — and heat the ice to temperatures of several thousands of degrees. That allowed the team to simulate conditions on Uranus, Neptune, and other planets with similar conditions where superionic ice could thrive.
“It’s as though the water ice is partially molten,” commented study co-author and University of California-Berkeley professor of earth and planetary science Raymond Jeanloz.
The new study differed from previous research on superionic ice, in the sense that the scientists were able to determine that the ice was opaque, based on its optical appearance. That allowed them to conclude that it was positively charged ions, instead of electrons, that were carrying the electrical current.
Although scientists were impressed by the surprising results study, which was led by Lawrence Livermore physicist Marius Millot, Science News noted that some experts raised some doubt, including Washington State University physicist Marcus Knudson, who was quoted as saying that he “[doesn’t] see strong evidence” that the superionic ice was able to melt, which it did once it reached 8,500 degrees Fahrenheit.
According to the New York Times, the researchers’ new discovery is important, as it could justify the unusual, unbalanced magnetic fields of Uranus and Neptune, which were last explored by NASA’s Voyager 2 mission in the 1980s. While Earth’s magnetic field is created at the planet’s core, things might be different in the two aforementioned outer planets in our solar system, as the magnetic fields could originate partly from superionic ice found in the objects’ mantles.