Searching for very old ice.
Searching for very old ice. Preston Cosslett Kemeny, Princeton Department of Geosciences

In an Antarctic ice core, made using a new strategy, scientists have found ice and bubbles of air that are 2.7 million years old. That’s astonishingly old ice, but it’s also dramatically older than any other pieces of ice humans have found before. Before this, the oldest ice we’ve ever found was one million years old.

What was the air like 2.7 million years ago? As Science News reports, the carbon dioxide levels in the air bubble samples was less than 300 parts per million, far lower than today’s rising carbon levels. That low concentration of carbon could have helped tip the planet into a series of ice ages; this very old ice can help scientists piece together the history of our planet

Usually, scientists drill ice cores with a continuous ice record—layers of ice each representing a year in Earth’s history. But there’s a limit to how far back those ice cores can go: Over time, the internal heat of the Earth melts the deepest, oldest layers of ice.

A Princeton geochemist, Michael Bender, figured out how to date ice that is not preserved in those clear layers. His technique involves measuring the argon and potassium trapped in the ice, and while it’s not precise—the results might be 100,000 years or so off—it can give scientists a rough idea of ancient ice’s age.

Armed with that technique, a Princeton team drilled into “blue ice” which is not preserved in organized layers but can contain much older ice. On their first try, they found that 1 million year old ice. (Previous to that, the record was 800,000-year-old ice.) On the second try, they found this sample, 1.7 million years older than the previous record. Next they may go after ice that’s 5 million years old, and it’s possible that there’s ice in Antarctica that’s 30 million years old

Just think about that—there’s ice somewhere on this planet that has been sitting frozen for 30 million, and someone might be able to find it.