When ultraviolet light hits ice—whether in Earth’s polar regions or on distant planets—it triggers a cascade of chemical reactions that have puzzled scientists for decades.

Now, researchers at the University of Chicago Pritzker School of Molecular Engineering (UChicago PME) and collaborators at the Abdus Salam International Center for Theoretical Physics (ICTP) have used quantum mechanical simulations to reveal how tiny imperfections in ice’s crystal structure dramatically alter how ice absorbs and emits light. The findings, published in Proceedings of the National Academy of Sciences, pave the way for scientists to better understand what happens at a sub-atomic scale when ice melts, which has implications including improving predictions of the release of greenhouse gases from thawing permafrost.

“No one has been able to model what happens when UV light hits ice with this level of accuracy before,” said Giulia Galli, Liew Family Professor of Molecular Engineering and one of the senior authors of the new work. “Our paper provides an important starting point to understand the interaction of light with ice.”