Space Ice Reveals a Hidden Structure: New Research Challenges Decades of Assumptions About Cosmic Ice

For many years, scientists believed that space ice—the ice that exists far beyond Earth, on comets, in the rings of planets, and in interstellar clouds—was a simple, disordered material, similar to frozen liquid water but without any crystalline structure. This view shaped countless theories about how planets form, how the universe evolves, and even how life might have arrived on Earth.

Now, a groundbreaking study by researchers from University College London (UCL) and the University of Cambridge has revealed that this belief was only part of the story. The most common form of space ice, known as low-density amorphous ice, actually contains countless microscopic crystals hidden inside its apparently chaotic structure.

These findings, published in Physical Review B, fundamentally change our understanding of amorphous ice in space and open new questions about the nature of water in the cosmos.

What Is Low-Density Amorphous Ice?

Low-density amorphous ice is not the familiar crystalline ice you see in a snowflake or in the ice cubes floating in your drink. Instead, it is formed when water vapor condenses on extremely cold surfaces—such as dust grains in interstellar clouds or the surfaces of comets—at temperatures below -110 degrees Celsius.

At these frigid temperatures, water molecules lack the energy to arrange themselves in neat, repeating patterns, leading to what scientists call an amorphous (without order) structure. For decades, researchers thought this form of ice was a frozen snapshot of liquid water, locking molecules randomly in place as they cooled.

But the new study demonstrates that the reality is more nuanced.

Tiny Crystals Concealed in Amorphous Ice

To uncover what really happens at the atomic level, the research team combined advanced computer simulations with laboratory experiments.

In their simulations, they cooled virtual boxes of water molecules to about -120 degrees Celsius at different rates. Remarkably, they discovered that the resulting ice structures were not entirely amorphous. Instead, up to 20–25% of the ice was actually made up of tiny crystalline regions—nanocrystals roughly 3 nanometers across, which is about as wide as a single strand of DNA.

This mixture of ordered and disordered regions closely matched X-ray diffraction data, which reveals how X-rays scatter when they hit the ice. The presence of these nanocrystals was the only way to make sense of the experimental measurements collected over the past decades.

Laboratory Evidence Confirms the Discovery

The scientists didn’t stop with simulations. They also created real samples of low-density amorphous ice in the lab, using several methods that mimic how ice forms in space:

Vapor deposition, where water vapor condenses onto a metal surface cooled far below freezing.
High-density amorphous ice warming, where dense amorphous ice created under compression is gently heated.

When these samples were warmed, their crystalline structure evolved differently depending on how the amorphous ice was originally formed.

According to Dr. Michael B. Davies, who led the work during his Ph.D. at UCL and the University of Cambridge, this variability was strong evidence that even the so-called amorphous ice retains a memory of its earlier form. If the ice were truly disordered, all samples would have crystallized identically when heated.

Why Does This Matter for Planetary Science?

Space ice is everywhere. It makes up much of the bulk material in comets, icy moons such as Europa and Enceladus, and the fine dust clouds where stars and planets are born.

Dr. Davies emphasized that understanding the precise structure of this ice is crucial:

“We now have a good idea of what the most common form of ice in the universe looks like at an atomic level. This is important because ice influences how planets form, how galaxies evolve, and how matter moves around the universe.”

For example, the porosity and crystallinity of ice can affect how organic molecules stick to it. This has direct implications for theories about the origin of life.

Space Ice and the Theory of Panspermia

One of the most fascinating ideas in astrobiology is Panspermia—the hypothesis that life’s building blocks were transported to Earth on icy comets. According to this view, molecules like amino acids could have been embedded within low-density amorphous ice during the early solar system’s chaotic formation.

But the new study suggests that space ice may not be as good a vehicle for life’s ingredients as previously believed.

Dr. Davies explained:

“A partly crystalline structure has less space for these molecules to become embedded. However, because amorphous regions still exist within the ice, the theory is not ruled out—just more complicated.”

This discovery urges scientists to rethink models of comet chemistry and the survival of delicate organic molecules over millions of years in space.

Amorphous Materials Beyond Ice

The implications of this research extend well beyond planetary science.

According to Professor Christoph Salzmann, co-author from UCL Chemistry, many advanced technologies rely on amorphous materials. For example, the glass fibers that transmit data across continents must remain disordered so that light doesn’t scatter unpredictably.

If these materials contain hidden nanocrystals, engineers may be able to improve their performance by controlling the amount and distribution of crystalline regions.

How Did the Researchers Simulate Space Ice?

The team created two main models to replicate low-density amorphous ice:

Gradual cooling simulations: Virtual boxes of water molecules were cooled slowly or quickly. Slow cooling allowed more time for nanocrystals to form.
Clustered crystal simulations: Small crystalline regions were packed closely together, and the spaces between them were disordered.

Both approaches led to remarkably similar structures: a mixture of amorphous and crystalline ice. The proportion of nanocrystals depended on how quickly the ice cooled—fast cooling produced mostly amorphous ice, while slower cooling created more ordered regions.

A Brief History of Amorphous Ice

Low-density amorphous ice was first identified in the 1930s when scientists condensed water vapor onto metal cooled to -110°C. High-density amorphous ice was discovered in the 1980s, created by compressing normal ice at temperatures near -200°C.

More recently, in 2023, the same team from UCL and Cambridge discovered medium-density amorphous ice, which surprisingly has the same density as liquid water and would neither float nor sink.

What Does This Mean for the Future?

Dr. Davies highlighted that ice in space is potentially a high-performance material. Not only could it serve as a radiation shield for spacecraft, but it could also be used to store fuel—hydrogen and oxygen can be extracted from ice by heating.

But to harness these properties, scientists must fully understand all forms of ice, including the interplay between disorder and hidden crystals.

Professor Angelos Michaelides from Cambridge concluded:

“Water is the foundation of life, but we still do not fully understand it. Amorphous ices may hold the key to explaining some of water’s many anomalies.”

Conclusion

This research challenges long-held assumptions about low-density amorphous ice and opens the door to new explorations in planetary science, astrobiology, and materials engineering. While space ice still holds many mysteries, one thing is now clear: it is not simply a frozen version of liquid water. Its hidden crystalline structures reveal that even in the coldest regions of the universe, order finds a way to emerge.

If you are fascinated by the physics of ice, the origin of life, or the development of advanced materials, this study offers a remarkable glimpse into a world we are only beginning to understand.

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Source: Phys.org

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