Perhaps I’m not quite ready to write this article, as it centers around the life and work of my late husband, Eric Erbe. For Eric, snow was always cause for celebration. As a boy, he rushed out to make snow forts and go sledding. As a budding adventurer in college, he discovered the thrills of cross-country skiing. Ultimately, his career as a prolific scientist and microscopist culminated in the development of a ground-breaking method for imaging and exploring the intricate shape of snow. Eric, my closest friend and life partner, was also my editor and adviser of all things science—and here I am without him to help tell this story.
As I watch the first snow of this season fall outside the window of our beloved mountain home in Davis, West Virginia, I put my secular self aside and take it as a nod of approval from beyond. I smile. “Just a skiff,” I hear him say. And a beautiful skiff at that, as the October snow clings to the remaining burnt-orange beech leaves and outlines every bare branch in a glistening frosting of solace.
Blizzard conditions aside, snow has a deceivingly gentle quality at times, tossed around by the mildest of air currents while silencing the landscape. But its arrival on the ground is only the beginning. When cold enough, snow can build into formidable snowpacks and grandiose glaciers. Nature’s own Bank of Life, each spring and summer loaning out our planet’s most precious currency: fresh water.
Snow is an odd character. As she dances effortlessly earthward, she is seen differently by those living in the latitudes that feel her touch. Children see a day off school while their parents see a glitch in the schedule. Skiers dream of sweeping turns down the mountain, artists rush to clutch the beauty in their lens, and city workers see overtime. Scientists see questions to be answered. One late December afternoon at a government lab in Beltsville, Maryland, Eric Erbe saw it all.
Eric was testing a newly installed cryo-stage for the lab’s low-temperature scanning electron microscope (LTSEM). Imagine a tall, hollow column of steel atop a large table, surrounded by a tangle of vacuum hoses, colorful cables, and shiny valves, all leading to a now ancient-looking computer with large cathode-ray tube monitors. Instead of using light like an optical microscope, the smaller bits of our world are revealed by an electron beam scanning a frozen platinum-coated specimen which ejects electrons of its own. That signal gets interpreted into black and white images that are captured on film. The new cryo-stage enabled viewing of samples at even colder temperatures near that of liquid nitrogen (-196°C/-321°F). While it sounds like something out of a 1950s sci-fi flick, the year was 1993.
As a leading microscopist at the United States Department of Agriculture (USDA), Eric spent his career in a windowless room revealing the curious, spectacular, and sometimes monstrous nature of the microscopic creatures that pestered the country’s agricultural industries. He also imaged the dangerous organisms that cause life-threatening diseases such as malaria and leishmaniasis. Collaborating with scientists on hundreds of papers, he offered them stunning photographic insight into the microscopic world. The flash-freeze technique enabled by the LTSEM meant the creatures were effectively suspended in animation—caught alive in the act of eating, mating, pestering, or just being. These were not thin-sliced pieces of dead tissue, but rather complete intact lifeforms, an alien-like Pompeii in extreme miniature (Fig. 1).
Eric more than made up for his days inside through his devotion to the outdoors. He was an explorer in the classic sense of the word, from wintery ascents in the European Alps to long, winding canoe trips through the Grand Canyon and countless runs on eastern whitewater rivers. He traversed endless slot canyons of the American Southwest following the dry, fickle rivers that created them. He lived for each winter here in Canaan Valley, meticulously planning and preparing new ski routes through his favorite forest on the planet. After 40 years of adventurous pilgrimages, he was finally able to retire and call West Virginia home.
Which brings us back to that December afternoon outside Eric’s lab where his two lives—scientist and outdoor adventurer—joined forces. The perfect solution for testing the new cryo-stage came to him while watching the snow fall. He chilled a sample holder, stepped outside, and held out the cold metal waiting to catch a falling snow crystal. Knowing him as I came to, I can only imagine the childlike curiosity and giddiness that likely made it hard for him to keep his hands still enough to collect the sample. Too bad it didn’t work.
The snow simply bounced off the chilled specimen holder. Even if he managed to catch the snow, how could he possibly expect the delicate crystals to survive the plunge into liquid nitrogen, the next step in preserving this elusive specimen? After several failed attempts, he opted to use a special liquid adhesive made for use in extremely cold temperatures. The snow fell gracefully onto the now sticky sample holder, settled in, and a few minutes later—swoosh! The cold chemical plunge sealed the deal. The snow crystal was ephemeral no more.
Kept at subfreezing temperatures, sputtered with platinum, and shot with an electron beam, the scanning lines revealed the broken and fractured symmetry of water’s most magical solid state. Photographically recorded onto polaroid film, humanity’s perception of snow was forever changed (Fig. 2).
Fig. 2. These two dendrites were captured in WV as they fell onto a cooled sample holder covered with a special cryo-adhesive.
Fig. 3. A classic example of rime and graupel.
Fig. 4. A depth hoar crystal from a snowpit in northern Minnesota.
Fig. 5. Crystals undergoing freeze/thaw in July from Loveland Pass, Colorado.
Fig. 6. Artificial snow generated by a snow gun in Vermont.
Fig. 7. Sample from a cross-country ski track in freshly fallen snow in West Virginia.
Fig. 8. Surface hoar or frost on a blade of grass in WV.
Fig. 9. Eight-sided crystals of CO2, a potential simulation of what forms on the polar caps of Mars. All micrographs by Eric Erbe
As a researcher, Eric knew he stood on the shoulders of those who came before him. When it came to snow, he was not the first to attempt to preserve its delicate beauty. Wilson A. Bentley spent almost 40 years at the turn of the 20th century perfecting his technique of snow crystal photomicrography in his chilly, outdoor shelter on a Vermont dairy farm. The classic dendritic snow crystals that represent the bulk of his work are colloquially known as “snowflakes” (Fig. 12), but this was just the beginning of cataloging and classifying snow. In 1954, Ukichiro Nakaya took Bentley’s homemade outdoor solution to the next level, building a laboratory where he imaged a wide variety of snow crystal types, expanding the visual library to include columns, bullets, needles, and other structures.
Modern images of snow crystals using light microscopy, such as the many published by Kenneth Lebbrecht, are quite enchanting. But looking at a snow crystal under an optical microscope poses some fundamental limitations from a scientific perspective. The observation itself has to be carefully managed so the sample doesn’t melt or sublimate. Moreover, successful light microscopy of snow is generally limited to a magnification of around 400 times with a very shallow depth of field.
LTSEM offered magnifications of up to 100,000 times with an almost infinite depth of field (Fig. 11). Eric’s novel collection method meant the snow samples could be collected intact, transported across thousands of miles, stored for years, and even left in the microscope for hours during observation. This afforded previously unheard-of opportunities for snow crystal imaging and study (Fig. 14).
The Handbook of Snow defines it as “particles of ice formed in a cloud which have grown large enough to fall with measurable velocity and reach the ground.” Or, as Eric, the secular humanist and avid cross-country skier would often say, “manna from heaven.”
Technically, snow is a subcategory of descending ice particles, not to be confused with hail or freezing rain. Snow crystals are the building blocks of snowflakes, which can contain dozens or even a couple hundred individual crystals. On the other hand, the crusty and crystalline beauty of rime, hoarfrost, and verglas, which all form directly on a cold surface, are in a league of their own. Hoarfrost seems to appear out of thin air on cold, clear nights as water vapor sublimates directly onto frozen objects—a direct and magical shift in H2O’s state from a gas to a solid. Rime, in contrast, describes supercooled water droplets or fog transforming into ice when contacting a cold surface. Verglas is a denser, glossier, and more transparent manifestation of this transformation.
Snow and rime are not mutually exclusive. They can join forces in the atmosphere as the snow crystal itself becomes a surface onto which rime can adhere. Given enough time, rime can overtake the snow crystal and lumpy balls of graupel form, (Fig. 3) creating a fascinating combination of meteorological phenomena. When even the slightest layer of graupel settles atop a hardened snowpack, we skiers know it’s time to drop everything and get outside.
Atmospheric temperature and humidity conditions define the infinite variety of snow crystal shapes, but this planet’s water-ice snow crystals are all six-sided. In our household, it was sacrilege to display an eight-sided snowflake decoration. Whether classic stellar dendrites (pg. 30), long, graceful needles (pg. 7), or blossom-like groups of bullets (Fig. 10), crystals are all based on the intrinsic hexagonal geometry of the water molecule. This is a simple fact of life, just as Earth is a spherical-ish planet revolving around the sun and 71% of its surface is water. This isn’t Mars, after all! But stay tuned, we’ll get there.
From that very first test with snow, Eric knew he was onto something, as did his USDA colleagues. This new method of viewing snow eventually came to the attention of another government agency—NASA. The masters of looking at Earth from space saw a unique way to help calibrate and validate snow and ice images from afar with on-the-ground imagery.
NASA?! Eric couldn’t believe it. At age 46, he was as enamored with NASA as when he was a young boy who turned a school research project into a massive four-inch binder full of newspaper clippings and lithographs he titled “Man in Space.” At age 16, he witnessed the Apollo 11 launch and humanity’s first moon landing live on TV. In 1970, his academic acumen and love of science was rewarded when he was selected to represent his high school at Cape Canaveral for the launch of Apollo 13. The ground-shaking, soul-rumbling experience of the Saturn V rocket’s mighty engines lifting off was transformative for Eric. On that bluebird afternoon as James Lovell, John Swigert and Fred Haise hurtled toward their ill-fated mission, Eric Erbe knew he was destined for a career in science.
NASA’s interest in snow was beyond seeing the picturesque crystals that fall during storms. They were creating water density models based on remote satellite observations of Earth’s snowpack. As snow ages on the ground, it changes significantly from fragile, frozen precipitation into blocky, thick, depth hoar (Fig. 4). In the spring, freeze-thaw action creates a conglomerate of rounded, slippery looking crystals (Fig. 5). These ever-changing states of snow confused the NASA computer models: the constant metamorphosis often made the water density of the snowpack hard to estimate. The highly detailed and unique view offered by the method Eric perfected in the LTSTEM provided much needed insight.
But why examine snow at all? Beyond contributing to ski area management, snow studies are used to estimate water availability for crop irrigation and predict potential flooding from a deep snowpack. In addition, understanding how snow crystals change within the layers of the snowpack helps experts identify and mitigate avalanche risks.
The partnership between USDA and NASA developed and quickly expanded. NASA was already examining a wide variety of snow-covered regions with ground observations and jumped at the idea of adding microscopy to the list. Eric was perfectly suited for this task as he had been a collector his entire life. As a boy there were fossils, butterflies, moths and rocks. Later, he amassed coins, stamps, records, and books. He collected soil samples on his weekend caving trips, as well as on a 40-day trek through the Himalayas in Nepal.
By working with NASA, he could escape the windowless room. He traveled all over the country, from Colorado to Minnesota to Alaska, collecting samples from snowpacks and glaciers. Trailing behind his long-legged, graceful, and efficient kick-and-glide was a sled full of collection supplies: a plastic snow shovel, dewars of liquid nitrogen, styrofoam cryo-work chambers, forceps, and custom copper storage devices.
Arriving at a site, Eric would join forces with the group to dig a snow pit, sometimes deeper than he was tall (Fig. 13). After collecting samples from the pit, he’d pack up, ski back, and ship home the snow samples in a special supercooled container. Back at the lab, he’d make himself a pour-over cup of coffee and examine the haul. His anticipation never waned; there was always a “hidden gem” to be discovered and shared.
“Eric was very intense, both in his outdoor life and his work life. There was never a down moment. He never quit,” recalled Doug Nace, one of Eric’s closest friends, a fellow outdoor adventurer, and former USDA colleague. Doug remembers traveling to West Virginia with Eric to go cross-country skiing while Eric simultaneously collected snow crystals. Classic Erbe.
Eric’s insatiable curiosity led him to collect samples beyond those that had obvious scientific value. What did artificial snow from a ski area look like? (Fig. 6) What about snow that had been compressed by the glide of a cross-country ski? (Fig. 7) Or hoarfrost decorating a single blade of grass? (Fig. 8) What might eight-sided, carbon dioxide-based snow crystals look like on Mars? (Fig. 9).
Snow, as a metaphor for life, is not an original idea. Fleeting, ephemeral, created in the outer reaches and then lost just beyond our grasp—crystals of snow and the human experience are often painted with the same brush. We are each uniquely imperfect formations, with an obvious beauty and exceptional relevance when truly seen and deeply observed.
Every snow crystal has a nucleating agent, a tiny particle to which water molecules cling as they become something greater. Sometimes, this particle drops out of the crystal, leaving a visible hole in its center (Fig. 15). Fortunately, the crystal remains for a while longer. Everything that was built around the particle is still tangible, visible, real.
Eric was such a particle himself, a nucleus around which I and so many others gathered and grew. Cancer dropped him out of our center way too soon. I’ve taken on the mantle of preservation to keep intact the delicate arms of his work so others may learn or, perhaps, simply appreciate the art and beauty of it all. Toward that goal, I’ve created www.SnowGallery.com, the supercooled dewar for his snow-related work. It’s likely to be quite an undertaking, but first I’ll make myself a pour-over coffee and check the forecast for snow (Fig. 16).
Victoria Weeks, founder of SnowGallery.com, is a digital artist and photographer living in Davis, West Virginia. Her late husband, Eric Erbe, was a great friend of the magazine and is sorely missed by all of us.
