Scientists create the most cubic form of ice crystals yet

Lab-made solid could give clues to climate change

Sun halos

SQUARED OFF  Halos around the sun may appear when cube-shaped ice crystals in clouds in the upper atmosphere scatter light (left). In the lab, nearly cubic ice crystals scatter X-rays into similar-looking concentric circles (right).

Left: Pixabay; Right: Courtesy of Ohio State University

Cube-shaped ice is rare, at least at the microscopic level of the ice crystal. Now researchers have coaxed typically hexagonal 3-D ice crystals to form the most cubic ice ever created in the lab.

Cubed ice crystals — which may exist naturally in cold, high-altitude clouds — could help improve scientists’ understanding of clouds and how they interact with Earth’s atmosphere and sunlight, two interactions that influence climate.

Engineer Barbara Wyslouzil of Ohio State University and colleagues made the cubed ice by shooting nitrogen and water vapor through nozzles at supersonic speeds. The gas mixture expanded and cooled, and then the vapor formed nanodroplets. Quickly cooling the droplets further kept them liquid at normally freezing temperatures. Then, at around –48° Celsius, the droplets froze in about one millionth of a second.

The low-temperature quick freeze allowed the cubic ice to form, the team reports in the July 20 Journal of Physical Chemistry Letters. The crystals weren’t perfect cubes but were about 80 percent cubic. That’s better than previous studies, which made ice that was 73 percent cubic.

Ashley Yeager is the associate news editor at Science News. She has worked at The Scientist, the Simons Foundation, Duke University and the W.M. Keck Observatory, and was the web producer for Science News from 2013 to 2015. She has a bachelor’s degree in journalism from the University of Tennessee, Knoxville, and a master’s degree in science writing from MIT.

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