The way ice forms is a lot more interesting than you think. This basic physical process, among the most common in nature, also remains somewhat mysterious despite decades of scientific scrutiny.

A cryomicroscopic image of a hexagonal ice crystal grown in a Fusarium acuminatum ice nucleator (IN) extract. Credit: PNAS

Now new research from the University of Utah, with Germany’s Max Plank Institute for Polymer Research and Idaho’s Boise State University, is shedding fresh light on the role of biological agents—produced by fungi of all things—in ice formation.

Contrary to what we have been taught in school, water won’t necessarily freeze at 0 degrees Celsius (32 degrees F) because of the energy barrier inherent in phase transitions.

Completely pure water won’t freeze until it cools to as low as -46 C. This is because water molecules require particles on which to build the crystals that lead to ice, a process called nucleation. Organisms have evolved various ways to control ice formation as an adaption to survive in cold environments.

So the most efficient ice-nucleating particles are biological in origin, produced in bacteria and fungi, and even insects, but the molecular basis and precise mechanisms of “biological ice nuclei” has not been well understood.

Valeria Molinero, a theoretical chemist with the University of Utah’s College of Science, is at the forefront of sorting out this mystery, which holds potential implications for improving our understanding of how life affects precipitation and climate.