Hot ice almost as hot as the surface of the Sun

American scientists have successfully created superionic ice in the laboratory for the first time. The research results were published in February in the journal Nature Physics, according toLive Science.

Researchers have long suspected that superionic ice, a high-pressure form of water ice, exists in the crusts of Uranus and Neptune, but that was only a hypothesis. "Our work provides experimental evidence for superionic ice and shows that the predictions are not based on simulations but actually reflect the unique behavior of water under extreme conditions," said Marius Millot, a physicist at Lawrence Livermore National Laboratory. Millot is the lead author of a study describing the experiment that created superionic ice.

Researchers first predicted the existence of this strange state of water that exists both as a liquid and a solid 30 years ago. Superionic ice is also much denser than regular ice because it forms only under the extreme temperatures and pressures found inside a giant planet. In its superionic state, the hydrogen and oxygen in water molecules behave unusually. Hydrogen ions move like liquids, inside a solid crystal lattice made of oxygen.

The process of creating superionic ice is complex. First, the team compressed water into a super-strong block of ice crystals, unlike regular ice cubes. To do this, they used a diamond anvil to create a pressure of 2.5 gigapascals, about 25,000 times the atmospheric pressure on Earth. Next, the researchers heated and compressed the anvil even more with lasers. Each ice crystal structure was exposed to six lasers at a pressure 100 times higher.

Once the superionic ice formed, the team quickly analyzed its optical and thermodynamic properties. They had just 10 to 20 nanoseconds to do their work before the pressure wave released the compressive force and melted the ice. The team found that the ice melted at 4,725 degrees Celsius and a pressure of 200 gigapascals. That’s about two million times the atmospheric pressure on Earth.

"It's unbelievable that water ice exists at temperatures of thousands of degrees Celsius inside planets, but that's what the experiments show," said Raymond Jeanloz, a planetary physicist at the University of California, Berkeley, and co-author of the study.

The new findings could shed light on conditions inside Uranus and Neptune. Planetary scientists speculate that water makes up 65 percent of the mass of these planets' cores, along with ammonia and methane.

Phuong Hoa