Tiny meteorites suggest ancient Earth had a carbon dioxide–rich atmosphere
Earth’s atmosphere 2.7 billion years ago may have been more than two-thirds carbon dioxide. That finding comes from a new study that simulates how the ancient atmosphere may have interacted with bits of cosmic dust falling through the sky. Such a carbon dioxide–rich atmosphere may also have created a powerful greenhouse gas effect, researchers suggest January 22 in Science Advances. That, in turn, could help answer a decades-old conundrum known as the “faint young sun paradox:” how liquid oceans could have existed on Earth when the sun was about 30 percent dimmer than it is now (SN: 4/18/13) Estimates for atmospheric carbon dioxide during the Archean Eon, which lasted from 4 billion to 2.5 billion years ago, vary widely. “Current estimates span about three orders of magnitude, from about 10 times more than now to a thousand times more,” says Owen Lehmer, an astrobiologist at the University of Washington in Seattle. So scientists have hunted for data that can shrink that range. Enter...