Uncovering the answer to an age-old question: how do snowflakes form?

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More than 400 years ago, renowned mathematician and scientist Johannes Kepler speculated about the creation of one of nature’s most angelic and unique shapes: the six-sided snowflake. Although atoms would not be discovered until two centuries later,  Kepler openly pondered about the microscopic building blocks that lead to the ice crystal’s hexagonal formation, including the myriad of factors behind this recurring phenomenon.  

More than 400 years ago, renowned mathematician and scientist Johannes Kepler speculated about the creation of one of nature’s most angelic and unique shapes: the six-sided snowflake. Although atoms would not be discovered until two centuries later,  Kepler openly pondered about the microscopic building blocks that lead to the ice crystal’s hexagonal formation, including the myriad of factors behind this recurring phenomenon.  

Now, research led by a Tufts University chemist has answered Kepler’s questions by shedding new light on this process by combining an electron backscatter with a large single crystal ice model. In a study published in the Proceedings of the National Academy of Sciences, scientists discovered that an ice crystal’s flat sides are formed by a hexagon that is larger and consists of a central water molecule surrounded by six others in the same layer. 

Mary Jane Shultz, Ph.D., a chemistry professor in the School of Arts and Sciences at Tufts University and first author of the study, said the chair-form hexagon has three molecules  in one layer and three more slightly lower in what is called a bilayer structure. The six flat sides of a snowflake grow from a hexagon formed within one layer. This larger hexagon is  rotated 30 degrees relative to the chair-form hexagon.

Read more at Tufts University

Image: This graphic reflects three scales: the macroscopic snowflake (blue lines), the molecular structure (red tube model), and the electron scattering diffraction (density plot). (Credit: Tufts University)