Strange kind of ice found inside many planets only melts at very high temperatures

When you reach into your fridge for an ice cube, or you view a chilly winter landscape dotted with icy formations, you're interacting with a substance we all know as ice, or scientifically known as hexagonal ice (Ice Ih). But what if i told you that there are about twenty different kinds of ice, each completely different from what you're familiar with? One form of ice is so unique it only exists deep within the mantles of celestial bodies like Neptune and Uranus. Introducing Ice XVIII, also known as superionic ice.

Professor Maurice de Koning published a study that explains the complexities of superionic ice and its potential to reveal more about the strange characteristics observed in our solar system's "ice giants."

Intriguing phenomenon of superionic ice

So, what makes superionic ice so special?

Ice XVIII is anything but ordinary. It's produced under extreme conditions -- temperatures as high as 5,000 Kelvin (about 4,700 degrees Celsius) and pressures approximately 340 gigapascals, over 3.3 million times the atmospheric pressure at Earth's surface.

Earth doesn't have these harsh conditions, but they are found deep inside the ice giants Neptune and Uranus , owing to their massive gravitational fields.

Within superionic ice, water doesn't maintain its typical molecular structure. The oxygen atoms form a rigid lattice, whereas the hydrogen atoms, now stripped of their electrons, float freely as positively charged ions.

"It's like a metal conductor such as copper, but with the positive ions forming the crystal lattice and the negatively charged electrons free to roam," explains de Koning, an esteemed professor at the Gleb Wataghin Physics Institute at the State University of Campinas in São Paulo, Brazil,

Why does superionic ice matter?

Superionic Ice or Ice XVIII captivates scientists due to its unique arrangement. The way these free-floating hydrogen ions move through the oxygen lattice could potentially explain unusual features of Uranus and Neptune, specifically, the peculiar behavior of their magnetic fields.

Unlike Earth, where the magnetic field aligns with its rotational axis, Uranus and Neptune have notably tilted magnetic field axes -- 47 and 59 degrees off their rotation axes, respectively.

This misalignment has puzzled scientists for a long time. De Koning's research infers that the movement of these protons through the superionic ice might be the cause.

He explains, "The electricity conducted by the protons through the oxygen lattice relates closely to the question of why the axis of the magnetic field doesn't coincide with the rotation axis in these planets."

Deep inside the mantles of "ice giants"

To investigate this theory further, De Koning and his team ditched traditional experimentation and turned to advanced computer simulations.

Using density functional theory (DFT), they modeled the mechanical properties of Ice XVIII to comprehend how it would behave under the intense conditions within Neptune and Uranus.

This task wasn't a walk in the park. Simulating ice XVIII required considering an overwhelming number of molecules -- around 80,000.

The calculations involved cutting-edge computational techniques, neural networks, and machine learning algorithms.

The primary objective was to discover how different types of defects in the crystal structure might correlate to large-scale deformations and thus, the mysterious magnetic fields.

Crystal defects and other imperfections

In the world of crystals , defects are typically seen as flaws that disrupt the normal atom arrangement. However, in superionic ice, these defects might be the key to its enigma.

The study investigated a specific defect type known as "dislocation," which happens when there's an angular difference between adjacent crystal layers.

De Koning uses a simple analogy, "imagine a rug that's been scrunched up; the resulting wrinkles are somewhat akin to dislocations in a crystal." He further explains, "Dislocation is to metallurgy what DNA is to genetics."

By simulating these dislocations within Ice XVIII, the team concluded the required force to cause the ice to deform could explain these planets' unique magnetic properties.

They found that the particular conditions within Neptune and Uranus, combined with Ice XVIII's properties, create the perfect environment for these phenomena.

Superionic ice in the lab

Despite sounding like a concept from science fiction, superionic ice is becoming increasingly critical to our understanding of the universe.

In 2019, scientists created a small amount of Ice XVIII by using high-powered lasers to compress a thin water layer between diamond surfaces -- an achievement that has opened up vast possibilities for future research.

For now, however, our understanding of superionic ice is primarily through simulations like the one led by De Koning.

He explains, "This was a most interesting aspect of the study, integrating knowledge in metallurgy, planetology, quantum mechanics , and high-performance computing."

Studying ice to learn about the universe

Understanding superionic ice not only satisfies our curiosity about what's inside distant planets, but can also revolutionize how we understand the fundamental physics that govern all matter.

As we uncover more about states like those found on Uranus and Neptune, we might discover new materials or properties that could have applications here on Earth -- from superconductors to new types of energy storage.

So, the next time you fetch an ice cube from your freezer, take a moment to appreciate the fascinating world of Ice XVIII. It's a reminder of how much we've yet to discover, in our universe and here on Earth.

The full study was published in the journal Proceedings of the National Academy of Sciences .

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