Eric Cravens, assistant curator at the National Ice Core Laboratory in Lakewood, Colorado, stands behind a wall of aluminum-encased ice cores. The ice in this room, kept at –33 degrees Fahrenheit, contains snapshots of atmospheric history dating back 440,000 years from various regions, including Antarctica and Greenland. “The ice core is an excellent record of the snowfall and atmosphere of a period of time,” says Ted Scampos, a climatologist who uses data from ice cores for his work. Dust found in the ice gives a record of what was in the air thousands of years ago, whether from volcanic eruptions or human activity, and the isotopic composition of the hydrogen and oxygen molecules in the snow give a record of the temperature of the earth at the time. Generally, more heavy isotopes mean a warmer climate. After a core is drilled, it is dried, wrapped in plastic, and slid into an aluminum-covered tube that reflects sunlight. The cores are then rushed to freezer containers before being shipped to California and trucked to Colorado. There they are kept until atmospheric scientists, astrophysicists, biologists, and other researchers request samples to help answer many unknowns in the history of our planet.