Water is an abundant and curious compound—unlike most other substances, it expands when it freezes. It’s also very complex; water can transform into more than a dozen different types of ice.
Now, scientists have confirmed the existence of a previously hypothetical form of water that is simultaneously liquid and solid. It’s called superionic water, and scientists have speculated that it lingers in the mantles of Neptune and Uranus.
Here’s Kenneth Chang, reporting for The New York Times:
Theorists first suggested 30 years ago that superionic water might exist under extremely high pressures and hot temperatures. The heat melts the chemical bonds between the hydrogen and oxygen atoms. The high pressure keeps the larger and heavier oxygen atoms stacked in a fixed crystal alignment—a solid—while the hydrogen nuclei, or ions, flow through—a liquid.
That makes it a conductor of electricity like a metal, but the current is carried by positively charged ions instead of negatively charged electrons.
In an experiment, scientists at Lawrence Livermore National Laboratory in California squeezed water between two pieces of diamond at a pressure of 360,000 pounds per inch. The water became a type of ice called ice VII, which is 60% denser than regular water. Each diamond cell also contained one-seven-millionth of an ounce of water. The researchers then penetrated the ice with laser light, sending shock waves through it about 10 to 20 billionths of a second in duration.
The result was a modest replica of conditions inside Uranus and Neptune (as well as other ice giants in other solar systems, most likely): temperatures reaching thousands of degrees and pressures at more than a million times that of Earth’s atmosphere.
The team was able to confirm that the end product was superionic because they captured its optical appearance. The sample was opaque, suggesting that ions were moving—not electrons.
The experiment was consistent with computational predictions—it could also explain the lopsided magnetic fields of Uranus and Neptune. Earth’s magnetic field is generated at its core; magnetic fields of icy bodies could be derived from shells of superionic ice inside the mantle.