Different Types of Ice
Learning about Isabel Pulido’s NanoFreeze technology, which is helping preserve food in rural Colombia, led me to take a closer look at the science of freezing. At first, it seemed simple—ice is just frozen water. But I soon found out that water can actually freeze into nearly 20 different solid forms, called “polymorphs.”
I knew that the element carbon has four different forms: the charcoal in my grill, the hard coal my great grandparents used to heat their house, the graphite in my No. 2 pencil, and the diamond in my mother’s wedding ring. Only when researching NanoFreeze technology did I learn the word polymorphs and that water has frozen polymorphs besides common, everyday ice.
Only two of these ice polymorphs naturally occur on Earth. The first is regular ice, the kind we use to cool drinks or that hockey players skate on. Scientists refer to this as Ice Iₕ (ice one h). The second naturally occurring form is cubic ice, or Ice I_c, which forms in the extremely cold upper parts of cirrus clouds—typically 8 to 12 kilometers (5 to 7.5 miles) above Earth’s surface—where temperatures can drop below –80 °C (–112 °F), far colder than anything we experience on the ground. Although cubic ice gradually changes into the more common hexagonal ice, it can last long enough to affect how cirrus clouds develop and reflect sunlight.
The other 18+ types of ice emerge under conditions so extreme they don’t naturally exist on Earth’s surface. Research into these forms began with German scientist Gustav Tammann who, around 1900, wasn’t specifically looking for new forms of ice. While studying water under pressure, he discovered Ice II—a denser, more tightly packed structure than normal ice. This accidental finding launched over a century of research into ice’s surprising versatility.
These exotic ice forms highlight water’s structural versatility under different conditions. Though Isabel’s innovation likely works specifically with common ice, these multiple forms show water’s remarkable adaptability.
Ice Beyond Earth: A Universe of Frozen Structures
Under extreme pressures and varying temperatures, water molecules form entirely new structures, creating exotic types of ice. As of 2024, scientists have identified at least 20 distinct ice polymorphs, including:
- The common ones: Ice Iₕ, Ice I_c
- The high-pressure forms: Ice II through Ice XV, formed in labs (and potentially existing in the deep interiors of icy moons like Europa and Ganymede).
- More recent discoveries: Ice XVI, Ice XVII, Ice XVIII, ultra-low-density and highly ordered forms created under special lab conditions
- Amorphous ices—disordered forms found in comets and space dust that lack the crystalline structure of typical ice.
Each ice polymorph represents a unique arrangement of water molecules based on surrounding conditions. The application of pressure can completely reorganize water’s molecular structure, creating substances with properties quite different from the ice in home freezers.
The count stands at 20+ varieties and is growing as researchers explore new frontiers in crystallography and planetary science. This remarkable variability raises intriguing questions about how nature might control ice formation in extreme environments—questions that parallel, though differ from, the biological mechanisms that inspired antifreeze technologies.
Why Exotic Ice Matters
These exotic ices aren’t merely scientific curiosities—they provide valuable insights across multiple scientific disciplines:
- Planetary Science: Ice structures in Jupiter’s moons might offer clues about potentially habitable environments. NASA’s upcoming Europa Clipper mission will specifically study these unusual ices.
- Climate Science: The behavior of different ice forms helps scientists predict how Earth’s polar regions respond to temperature changes—crucial knowledge for climate modeling.
- Materials Science: Understanding ice polymorphs contributes to the broader field of materials science, potentially inspiring new technologies with unique properties.
While Isabel Pulido’s NanoFreeze technology likely works specifically with antifreeze proteins that either prevent or control common ice formation rather than exotic polymorphs, both fields reflect the broader scientific understanding that water’s solid state can be manipulated through various mechanisms.
The Expanding World of Ice
The study of ice polymorphs and antifreeze proteins reveals how a seemingly simple substance—frozen water—contains remarkable complexity. From common household ice to the exotic ices deep within distant moons, to precisely controlled freezing in technologies like NanoFreeze—each shows water’s incredible versatility.
The next post will explore antifreeze proteins in greater detail—the remarkable molecules that prevent Antarctic fish from freezing in sub-zero waters and that enable Isabel Pulido’s food preservation technology. This exploration will examine how these proteins work at the molecular level to promote ice formation and how understanding them might lead to additional breakthroughs in medicine, agriculture, and food preservation.
The story of ice reminds me that even familiar substances often hold extraordinary secrets—secrets that designers can use to create innovative solutions for real-world challenges.
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Read about discoverers like Isabel Pulido in Teen Innovators: Nine Young People Engineering a Better World with Creative Inventions. Learn about a creative problem-solving method like hers in Design Thinking: A Guide to Innovation.