Around the world, a small group of secluded libraries contain some of the rarest and most fragile objects on Earth.

They’re staffed by scientists, equipped with redundant power supplies… and kept very, very cold.

That’s because the ‘books’ in these libraries are ice cores.

They’re collected in some of Earth’s harshest environments, like Antarctica and Greenland, at great cost, then transported frozen to these libraries.

Each core is one of a kind. And once it’s been read – small samples melted to reveal its secrets – it can never be replaced.

But those secrets make all this worthwhile. Because the glaciers and ice sheets the cores came from have captured, over endless seasons, the history of our planet.

Layers of ash reveal the timing, and geological makeup, of ancient volcanic eruptions.

Pollen samples reveal global plant populations, as they’ve changed over millennia.

Black carbon deposits tell of forest fires.

Trapped isotopes of oxygen and other gases paint a picture of past atmospheres.

The top layers, representing the most recent few thousand years, record humans’ influences on Earth: traces of agriculture, industry or war that carried on winds and settled on the ice.

These ice cores, and the libraries that preserve them, are simply irreplaceable, providing a nearly 3-million-year window into Earth’s past.

Now that’s some cool science.