Ancient bubbles in Pilbara rock show Earth had thin atmosphere 2.7b years ago

Air bubbles trapped in 2.7 billion-year-old lava flows in the Pilbara suggest the Earth's atmosphere weighed less than half that of today and was far thinner than previously thought. The discovery has forced a rethink of how the Earth managed to stay relatively ice-free during that period, despite the Sun being much cooler than it is today.