Two-billion-year-old salt rock reveals rise of oxygen in ancient atmosphere

A 2-billion-year-old chunk of sea salt provides new evidence for the transformation of Earth's atmosphere into an oxygenated environment capable of supporting life as we know it. The study by an international team of institutions including Princeton University found that the rise in oxygen that occurred about 2.3 billion years ago, known as the Great Oxidation Event, was much more substantial than previously indicated. "Instead of a trickle, it was more like a firehose," said Clara Bl├Ąttler, a