EVERYTHING WORTH Ice KNOWING It’s everywhere! BY SIDNEY PERKOWITZ We typically encounter ice as cubes floating in a glass of something nice to drink. But more than just a party staple, ice is a significant part of our planet and the universe — a fundamental substance that deeply affects us, and may even be connected to the origins of life. Talk about refreshing! EARTH . No-Tech, Low-Tech and High-Tech Americans love ice. We make desserts out of it, put it in drinks and expect motels to provide it by the bucketful. But before ice-making technology, it was a precious commodity laboriously harvested from nature. In the early 19th century, American entrepreneur Frederic Tudor began shipping ice cut from New England ponds to warm climates like the West Indies. He eventually became the “Ice King,” selling thousands of tons of ice throughout the U.S. for iceboxes, which preserved food. Natural ice remained profitable until a century ago with the arrival of electric refrigerators, which exploited the cooling properties of evaporating liquids. Those white boxes with clumsy cooling units have evolved into sleek stainless steel models, but we still harvest ice. High-end drinkers want premium, artisanal ice in their craft cocktails — perfectly clear, oversized cubes that look good and supposedly melt slowly to avoid dilution. While these can be created in-house, it’s a time-consuming process, so specialty companies now provide this elaborate ice. The cubes are hand-cut from big blocks of filtered water gradually frozen in special units for days, a process that eliminates the air bubbles that produce cloudiness. The cost? A whopping $1 each. The Ice King would be green Workers harvest ice from a frozen lake in the with envy. northern U.S. in the 1930s. Artisanal ice is cut with a band saw and shaped into clear cubes without bubbles for drinks at the Half Step bar in Austin, Texas. CLOCKWISE FROM TOP: KEYSTONE-FRANCE/GAMMA-RAPHO/GETTY IMAGES; BILL MCCULLOUGH (2); VALENTYN VOLKOV/SHUTTERSTOCK VALENTYN BILL MCCULLOUGH (2); IMAGES; KEYSTONE-FRANCE/GAMMA-RAPHO/GETTY TOP: CLOCKWISE FROM 66 DISCOVERMAGAZINE.COM A Most Complicated Mineral Ice is not just the solid form of water. By definition, natural ice is a mineral, like quartz: a naturally occurring inorganic solid with an ordered atomic structure. Or rather, structures. It appears in at least 18 different crystalline forms, plus amorphous forms where the atoms are randomly arranged. The variety that cools our drinks, hexagonal ice or Ih, is the most common type, but it’s also quite unusual. Unlike most solids, its frozen state is less dense than its liquid state, thanks to the hexagonal atomic geometry. That means frozen water floats on liquid water — not the case for almost any other substance. The geometry is the reason icebergs float, and helps explain why bodies of water don’t freeze solid from the bottom up, allowing aquatic life to survive winters. Common ice also appears as snowflakes, which take on hexagonal forms in atmospheric water vapor. Less well known Atomic structure of hexagonal ice is hair ice, which grows in fine filaments on wood infested with a specific fungus. Other exotic ice structures are made in the lab. Researchers recently found that squeezing room-temperature water between atom-thick sheets of carbon locks the water molecules into a two- dimensional square array to form a new kind of ice. Kurt Vonnegut’s novel Cat’s Cradle featured Ice-Nine, a fictional version of ice that would instantly crystallize all water, potentially dooming the world. While there really is an “ice- nine,” it forms only under high MACKEY/DISCOVER AFTER CANADIAN GEODETIC SURVEY/NATURAL RESOURCES CANADA AFTER CANADIAN GEODETIC SURVEY/NATURAL MACKEY/DISCOVER pressure and low temperature, and does not “lock up” all water. Hair ice Reshaping the World POST-GLACIAL REBOUND Earth’s massive ice stores are melting, thanks in part to global warming, and we’re seeing the effects on our planet. One of the biggest concerns Flexing Ice upward is the accompanying rise in average global sea level — estimated at 3 to 6 feet by 2100. But other problems pop up with some 400 billion tons of Greenland and Antarctic ice turning into water each year since 2011. Loaded crust First, there’s something called post-glacial rebound. Ice piled onto a “sinks” landmass presses it down into the squishy mantle layer below Earth’s crust. As our world warms, the formerly icy areas rebound, literally raising the land up. That’s one reason for the varying sea level rises along Mantle flows outward different coasts. Also, the weight of all that ice had slightly flattened the whole planet. (A single glacier can weigh millions of tons.) Rising temperatures caused Global sea it to start becoming spherical again. This influenced Earth’s rotation, level rising akin to an ice skater jutting out her arms to spin slower, contributing Collapsing toward a lengthening of the day by milliseconds over the past 2,500 years. It also alters the planet’s axial tilt: The North Pole had been steadily wandering toward Canada, but researchers recently realized that the current ice melt has jolted it on a new course toward the Crust rebounding United Kingdom, at an accelerated rate of 7 inches a year since 2000. Astronomers’ stellar observations and your phone’s GPS program have to Mantle flows back take this effect into account. FROM TOP: KENNETH LIBBRECHT/SCIENCE SOURCE (3); UMARAZAK/SHUTTERSTOCK; GISELA PREUSS VIA THE EUROPEAN GEOSCIENCES UNION; ALISON THE EUROPEAN GEOSCIENCES UNION; VIA GISELA PREUSS UMARAZAK/SHUTTERSTOCK; KENNETH LIBBRECHT/SCIENCE SOURCE (3); TOP: FROM July/August 2017 DISCOVER 67 EVERYTHING WORTH KNOWING Ice . AND BEYOND Water, Water Everywhere Europa, Enceladus and other moons of Jupiter and Saturn have ice in abundance. In 2015, NASA’s New Horizons mission to Pluto spectacularly confirmed that the entire solar system boasts water ice, as well as other frozen volatile materials. The composition of these ices sheds light on the properties of their home worlds and gives clues to how the solar system formed some 4.6 billion years ago. Near the sun, Mercury has water Mars’ cold temperatures support ice preserved within craters in water ice, including on its North Pole. Plates of ice churn and break apart on Europa (above), while Enceladus permanent shadow. (Similar ice (below) boasts an icy, fractured surface. appears on Earth’s moon.) Venus, the hottest planet, can’t Larger bodies in the asteroid belt, like claim water ice, but astronomers Ceres and 24 Themis, appear to be full of were surprised to find several water ice — in fact, Ceres may have more Saturn’s rings are types of snow were possible. fresh water than Earth! practically nothing but water ice. Ceres’ icy volcano, Ice could one day power Ahuna space exploration. Methane, Mons found throughout the solar system, combines with liquid oxygen to yield a type of rocket fuel. That means spacecraft might someday hop through the solar system, refueling from methane ice deposits along the way. BACKGROUND: LISA ALISA/SHUTTERSTOCK. IMAGES: NASA IMAGES: ALISA/SHUTTERSTOCK. LISA BACKGROUND: 68 DISCOVERMAGAZINE.COM could then easily combine with oxygen, The sun has Water’s Envoy e- forming our H2O ice. a much lower Planetary scientists tested this by deuterium Clearly, water ice is more abundant p examining the hydrogen atoms in today’s than we once thought. But did our water. Deuterium, a type of hydrogen concentration solar system just get lucky? And where Hydrogen with a neutron, is heavier than regular than our did it come from in the first place? The hydrogen. Scientists can classify water oceans, answers lie within water itself. samples, and compare their histories, by suggesting The components of water ice e- learning how many of those hydrogen atoms that much of — hydrogen and oxygen atoms — are deuterium. They’ve found that the ice Earth’s water have been around for much of the p on comets has deuterium concentrations universe’s history, but of course it’s n very similar to the water in our oceans. comes directly not water till they’re combined. from the initial Deuterium The match means our water ice stores have Astrophysicists think that happened the same cosmic origin as the solar system’s pre-solar cloud. during the earliest days of our solar comets — among its oldest known objects. Just think: Part system, when the sun and planets were So, we know our watery bounty is not unique, of every sip nothing more than a swirling cloud of hydrogen since the same conditions likely occurred during of water you and dust particles. If high-energy particles from the formation of any other solar system. Water drink could be deep space, called cosmic rays, happened to hit is likely similarly abundant around other planets, one of those hydrogen atoms, it became ionized, raising the odds of finding life as we know it, or older than the stripped of its electron. Ionized hydrogen atoms at least habitable conditions, somewhere else. sun. Pluto and other Kuiper Ice, Ice, Baby? Belt objects also boast Ice may be responsible for life itself. By analyzing the light from molecular surface and clouds, astronomers have observed not just H2O, but 200 different molecules subsurface — including H2, carbon dioxide and ammonia — existing either as gases or in collections ice that coats dust grains. These molecules can interact to produce complex of ice. organic compounds, which could generate DNA, RNA and amino acids. Such biomolecules or their precursors could have ridden to Earth on comets or asteroids to seed life on our planet — and possibly elsewhere.