Early Earth’s atmosphere was way lighter

Image: Australian rock
The layers on this 2.7 billion-year-old rock, a stromatolite from Western Australia, show evidence of single-celled, photosynthetic life on the shore of a large lake. The new result suggests that this microbial life thrived despite a thin atmosphere. (Credit: Roger Buick / UW)

Tiny bubbles that were trapped inside 2.7 billion-year-old rocks have led scientists to conclude that Earth’s atmosphere was less than half as dense as it is today – which runs counter to conventional wisdom.

Scientists had assumed that our planet’s atmosphere was thicker billions of years ago, in order to retain heat and keep the planet warm enough for life during an era when the sun shone less brightly than it does today.

“Our result is the opposite of what we were expecting,” Sanjoy Som, an astrobiologist at NASA’s Ames Research Center in California, said in a news releasefrom the University of Washington.

Som is the principal author of a study reporting the findings, published today by Nature Geoscience. He conducted the research during his doctoral studies at the UW, and retains a Seattle connection as the CEO of a nonprofit space science outreach group called Blue Marble Space.

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By Alan Boyle

Mastermind of Cosmic Log, contributing editor at GeekWire, author of "The Case for Pluto: How a Little Planet Made a Big Difference," president of the Council for the Advancement of Science Writing. Check out "About Alan Boyle" for more fun facts.

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