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

From ABC Science, 10 May 2016:

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.

In a study published today in Nature Geoscience, researchers analysed the relative sizes of air bubbles across ancient lava flows along the Beasley River in Western Australia’s Pilbara region.

The lava flows — discovered by Australian researcher Dr Tim Blake, then at the University of Western Australia — bear distinctive features such as lava “toes” with cracked, glassy rinds, which suggested the molten rock once flowed over a beach. Read more.

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