Earth’s rocks hold whiffs of air from billions of years ago
Earth’s atmosphere, the veneer of gases that makes most life possible, has changed dramatically over time. Bubbles of ancient air trapped in polar ice cores provide reliable archives of the past 6 million years —but that’s less than 0.2% of Earth’s history. For the eons before that, which saw the origin and proliferation of life, researchers have had to infer the atmosphere’s composition from evidence of its chemical effects on metals and minerals preserved in ancient rocks. But now a small group of researchers is taking a more direct approach: analyzing minute pockets of ancient liquid and gas trapped inside salts, veins of quartz, and crystallized magma. From samples that stretch back more than 3 billion years, they’re extracting direct records of noble gases, oxygen,...
