Episode Summary
Executive Summary: The episode explores why ice is scientifically unusual and how researchers have discovered an expanding family of ice phases under varying pressures and temperatures. It focuses on recent findings, especially ice 21 and the proposed ice 22, showing that water can form increasingly complex crystalline structures with implications for planetary science, materials research, and understanding phase transitions.
Main Topics: Why ice is strange despite being familiar (Priority: 5/5): Ice is highlighted as an odd substance because it floats, has multiple crystalline forms, and still reveals new properties such as slipperiness and unexpected phase behavior. Water structure and hydrogen bonding (Priority: 5/5): The discussion explains the bent H2O molecule, electron repulsion, and how hydrogen bonding creates repeating crystal lattices when water freezes. Ice phase diagram and pressure effects (Priority: 5/5): Different ice phases emerge from combinations of temperature and pressure; increased pressure can force molecules into denser structures beyond familiar ice 1H. Newly discovered complex ice phases (Priority: 5/5): Recent work identified ice 21 and a possible ice 22, with highly complex repeating units, plus unusual phases like plastic ice 7 and superionic ice 18. Why scientists care about exotic ice (Priority: 4/5): These phases matter for modeling icy moons and planets, understanding magnetic fields, and controlling crystal structures relevant to pharmaceuticals. Experimental tools enabling discovery (Priority: 4/5): Diamond anvil cells, X-ray free-electron lasers, and neutron scattering allow researchers to create and identify these fleeting, high-pressure phases. Future of ice discovery and simulations (Priority: 4/5): Simulations suggest tens of thousands of possible phases, implying that the number of known ice forms may keep increasing as experimental methods improve.
Key Arguments: Ice is not a single substance in practice but a family of phases whose structures depend on pressure and temperature. The molecular geometry of water and hydrogen bonding explain why ice forms crystalline lattices and why those lattices can vary. High pressure is the main route to discovering exotic ice phases, often in combinations with carefully controlled temperature. Some ice phases are metastable, meaning they briefly appear during phase changes even if they are not the most stable form. New phases are scientifically important for planetary modeling, especially for icy planets and moons where extreme conditions are common. Understanding ice phases also helps crystal science more broadly, including the production and stability of pharmaceutical compounds. Computational simulations predict many more possible ice phases than have been experimentally observed, suggesting future discoveries are likely.
Data Points: Known ice phases at turn of the 20th century: 12 - The episode notes the count of recognized ice phases around 1900. Known phases of ice in 2019: 18 - Ice 18, also called superionic ice, was reported around 2019. Fully confirmed ice phases now: 21 - The guest states that 21 phases are fully confirmed and peer-reviewed. Potential newest phase: 22 - A 22nd phase is described as undergoing peer review. Repeating unit in ice 21: 152 water molecules - Ice 21 is described as the most complex confirmed ice phase. Repeating unit in ice 22: 304 water molecules - The proposed ice 22 is even more complex than ice 21. Approximate temperature for plastic ice 7: around 500 degrees Celsius - Plastic ice 7 appears when ice 7 is heated to a very high temperature. Ice 1C occurrence: rare, in upper atmosphere/plane contrails - Cubic ice is said to form briefly in extremely cold atmospheric conditions. Length of European X-ray Free Electron Laser Facility: three and a half kilometers - The facility used to take X-ray images of the ice structure. Year of ice 9 discovery: 1968 - Mentioned in response to a Kurt Vonnegut reference.
Pivotal Quotes: "we keep finding new kinds of ice, and they keep getting weirder" — Shalma Wegsman: Summarizing the central thesis of the segment on expanding ice phases. "the simplest repeating block, is made up of 152 water molecules" — Shalma Wegsman: Describing what makes ice 21 unusually complex. "as long as we look, we'll keep finding more of them" — Shalma Wegsman: On why simulations and theory suggest more ice phases remain undiscovered.
Implications: Listeners learn that even familiar water can hide immense structural complexity. For science and industry, improved high-pressure experiments could reveal more ice phases, refine planetary models, and improve control over crystal formation in materials and drugs.
About Quanta Science
Exploring the distant universe, the insides of cells, the abstractions of math, the complexity of information itself, and much more, The Quanta Podcast is a tour of the frontier between the known and the unknown. In each episode, Quanta Magazine Editor-in-Chief Samir Patel speaks with the minds behind the award-winning publication to navigate through some of the most important and mind-expanding questions in science and math. Quanta specifically covers fundamental research — driven by curiosi...