Earth got first whiff of oxygen 3.2 billion years ago
Rock record shows signs of oxidation 200 million years earlier than previously thought

OXYGEN’S ORIGINS The first whiff of oxygen in Earth’s oceans came 200 million years earlier than previously known, new research finds. The oxygen-expelling organisms responsible were probably the forebears of modern cyanobacteria, shown.
Nancy Nehring/iStockphoto
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