Strange Form of Ice Found That Only Melts at Extremely Hot Temperatures

Strange things happen within planets because they contain familiar elements under intense heat and pressure.

It is possible that iron atoms dance in the solid Earth's inner core, while hot, black, heavy ice that is simultaneously solid and liquid develops in the water-rich gas giants, Uranus and Neptune.

Superionic ice is a unique ice that was initially replicated in lab tests five years ago. Its existence and crystalline structure were verified four years ago.

Then, barely a year ago, scientists from the Stanford Linear Accelerator Center laboratory in California (SLAC) and a number of American institutions found a new phase of superionic ice.

Their finding adds to our knowledge of why the magnetic fields of Uranus and Neptune are so asymmetrical and contain many poles.

You might mistakenly believe that water is a straightforward, elbow-shaped molecule composed of one oxygen atom and two hydrogen atoms that solidify into place when water freezes based on our planet's surroundings.

Superionic ice is notably distinct, yet it could be among the most prevalent types of water in the universe; it is thought to be present in the innards of comparable exoplanets as well as Uranus and Neptune.

The innards of these planets are as hot as the surface of the Sun, with pressures up to two million times that of Earth's atmosphere. This is where the strange water is found.

2019 saw the confirmation of physicists' 1988 prediction: a structure in which charged hydrogen atoms are allowed to travel through the solid cubic lattice of superionic ice like electrons through metals, while oxygen atoms are trapped in a solid cubic lattice.

This explains the conductive characteristics of superionic ice. Additionally, it increases the melting point of the ice, keeping it solid even at extremely hot temperatures.

In the most recent investigation, Stanford University physicist Arianna Gleason and associates used incredibly strong lasers to blast tiny water slivers that were encased between two layers of diamonds.

The pressure and temperature were elevated to 200 GPa (2 million atmospheres) and about 5,000 K (8,500 °F) respectively via a series of shockwaves. This temperature rise was higher than the 2019 trials, but at a lower pressure.

In their study dated January 2022, Gleason and colleagues state that "recent discoveries of water-rich Neptune-like exoplanets require a more detailed understanding of the phase diagram of [water] at pressure–temperature conditions relevant to their planetary interiors."

The crystal structure of the heated, thick ice was subsequently exposed by X-ray diffraction, even though the pressure and temperature conditions were only sustained for a brief period of time.

The ice crystals were in fact a novel phase different from superionic ice reported in 2019, as the ensuing diffraction patterns verified. In comparison to its 2019 predecessor, Ice XVIII, the newly found superionic ice, Ice XIX, has a body-centered cubic structure and higher conductivity.

Because magnetic fields are created by moving charged particles, conductivity is crucial in this situation. This is the fundamental idea of dynamo theory, which explains how magnetic fields are created by churning conductive fluids inside celestial bodies like the Earth's mantle or inside other bodies.

The type of magnetic field generated would differ if a mushy solid occupied a larger portion of the inside of a Neptune-like ice giant than a spinning liquid did.

Even crazier, if the planet's core included two superionic layers with varying conductivities, as Gleason and colleagues speculate Neptune may have, then the magnetic field created by the outer liquid layer would interact differently with both of them.

The increased conductivity of a superionic ice layer similar to Ice XIX, according to Gleason and colleagues, would encourage the creation of erratic, multipolar magnetic fields similar to those emitted by Neptune and Uranus.

If accurate, the findings would come more than thirty years after NASA's Voyager II spacecraft, which was launched in 1977, passed by the two ice giants in our Solar System and detected their incredibly peculiar magnetic fields.

The study was published in Scientific Reports.