Mystery Image Contest: December 2-16, 2013

Answer

Most people have probably grown up hearing that "no two snowflakes are alike," but this fact was not always common knowledge. Beginning in the early 1600s in Europe, mathematicians and philosophers like Johannes Kepler and Rene Descartes observed the hexagonal shape of most snowflakes and their seeming uniqueness, though they were limited by what they could see with the naked eye. Neither could quite believe that every individual snowflake could be one-of-a-kind. It wasn't until the invention of the microscope in the later 1600s, and, much later, the invention of photography, that people were able to see and study snowflakes more closely. For instance, Wilson "Snowflake" Bentley was an American farmer who became famous in the early 1900s for carefully photographing over 5000 individual snowflakes, showing that no two were alike. In the mid-1900s, Japanese physicist Ukichiro Nakaya greatly advanced scientific understanding of snow crystal formation by studying natural snowflakes in great detail and then discovering how to "grow" artificial snowflakes in the laboratory. Nowadays, images of snowflakes like the one above are taken with low-temperature scanning electron microscopes (LT-SEM) which offer much more detail than any traditional cameras or microscopes. To use LT-SEM to capture snowflakes, snow or ice samples are placed on copper sample plates and then submerged in liquid nitrogen to keep them frozen at -196 degrees Celsius. Keeping the samples at this temperature stops the snowflakes from melting or being damaged before they can be photographed. When they are ready to be photographed, the samples are coated with a very thin layer of platinum, which makes them electrically conducive and allows them to be visible to the LT-SEM. LT-SEM allows for taking images at extremely high magnification, allowing for the sort of detail you see in the picture chosen for this Mystery Image Contest.

Description

This image is of a snow crystal (aka a snowflake) as captured by a scanning electron microscope.

Photo Credit

Electron and Confocal Microscopy Lab, Agricultural Research Service, U.S. Department of Agriculture

Winning Entry

Our winners are:
Ms. Day/Mrs. Cumps' 8th grade, Petersburg, AK
Candy Durham, Dalton State College, GA

For Educators

Teaching Support

We've all heard that no two snowflakes are alike. But, many probably wonder how snowflakes are formed. What is the science behind snowflakes and snow crystals? A snow crystal is a single crystal of ice whereas a snowflake can be an individual snow crystal, a few snow crystals stuck together, or large clusters of snow crystals. The most basic form of a snowflake is a hexagonal prism and snowflakes form from water droplets in the air. When one of those droplets freezes, it becomes a small particle of ice. As it grows, water vapor condenses onto its surface. This process forms a snowflake.

This time of year is perfect for discussing snowflakes, ice, and frost with your students. And, our Mystery Image for this month makes a perfect tie-in for those concepts. You can use the snow crystal image to generate discussion around the concept of atoms and how atoms can be packed together in crystal patterns. The image also could be used to discuss the different phases of water—from liquid to solid to gas—and how the atoms of water behave in those different phases. You also could take your students outside on a snowy day and have them try to examine some snowflakes under an 8-10x magnifying glass. You first might want to freeze some black construction paper. Then, students could put down the black construction paper to catch the snowflakes and carefully examine them under the magnifying glasses.

The Science NetLinks lessons listed here can help expand on the concepts in this Mystery Image.

Related Resources

Science NetLinks Mystery Image Contest Rules and Regulations