Life may have been possible in Earth’s earliest, most hellish eon | Science News

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Life may have been possible in Earth’s earliest, most hellish eon

New analyses suggest heat caused by asteroid bombardment didn’t sterilize the planet

By
7:00am, January 26, 2018
illustration of hellscape

FIERY MYTH  Scientists have long thought that Earth was a sterile hellscape during its earliest eon (illustrated), due to asteroid bombardment. But the heat from those impacts wasn’t too much for life to exist, new research indicates.

Maybe Earth’s early years weren’t so hellish after all.

Asteroid strikes repeatedly bombarded the planet during its first eon, but the heat released by those hits wasn’t as sterilizing as once thought, new research suggests. Simulations indicate that after the first few hundred million years of bombardment, the heat from the impacts had dissipated enough that 10 to 75 percent of the top kilometer of the subsurface was habitable for mesophiles — microbes that live in temperatures of 20° to 50° Celsius. If so, the planet may have been habitable much earlier than previously believed.

Earth’s earliest eon, the Hadean, spans the period from about 4.6 billion years ago, when the planet was born, to 4 billion years ago. The name, for the Greek god of the underworld, reflects the original conception of the age: dark and hellish and inhospitable to life. But little direct evidence of Hadean asteroid impacts still exists, limiting scientists

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