A core drilled in Antarctica in 2015 has yielded 2.7-million-year-old ice, an astonishing find 1.7 million years older than the previous record-holder. Bubbles in the ice contain greenhouse gases from Earth's atmosphere at a time when the planet's cycles of glacial advance and retreat were just beginning, potentially offering clues to what triggered the ice age. While the discovery does not offer a continuous record of carbon dioxide in the ancient atmosphere like traditional ice cores, its "snapshots" will help calibrate proxies gleaned from the fossils of animals that lived in shallow oceans. The discovery also points the way to finding even older ice, because it comes from a largely ignored "blue ice" area, where peculiar dynamics can preserve old layers. Such records could reveal a time in Earth's past when temperatures are thought to resemble where the planet is headed with human-driven warming.