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Snowflakes begin to form when water droplets freeze onto small particles of dust or microorganisms including bacteria, fungi or pollen grains. This creates tiny ice crystals, and as they fall to the ground, water vapor freezes onto them, and gradually builds snowflakes with unique patterns. Interestingly, bacteria such as Pseudomonas syringae that are the best at forming snowflakes have a protein on their surfaces that enhances ice nucleation. These atmospheric microorganisms or “biological ice nucleators” are ubiquitous, and are thought to influence the hydrogeological cycle of the earth.
For more on the role of microorganisms in making snowflakes, watch “I Contain Multitudes”
This snowflake, around 2 mm in diameter, was manufactured in the laboratory using tiny ice crystals generated in a freezer. Interestingly, it is possible to produce almost identical snowflakes in the controlled conditions of the laboratory!
For more details on making snowflakes see
and movies of snowflakes growing in the lab.
Kenneth G. Libbrecht, PhD, Department of Physics, Caltech, Pasadena, California