The missing 500 million: Cosmic bombardment melted Earth's first crust
SMRTR summary
Billions of years ago, the ground beneath your feet may have been forged not from Earth's interior, but from the sky falling down.
A team of geologists, led by Tim Johnson at Curtin University in Perth, Australia, is arguing that ancient asteroid bombardment, not plate tectonics or volcanic plumes, created the conditions necessary for Earth's continents to form.
By studying impact craters on the Moon and scaling that data to early Earth, the team calculated that thousands of asteroids larger than 10 kilometers struck our planet during the Hadean eon. The heat was staggering, dwarfing internal sources by roughly ten times.
That heat kept the crust thin, molten, and impossible for plate tectonics to take hold. Only as impacts declined, around 3.5 billion years ago, did the crust thicken enough to build continents.
"As soon as you can create thick crust," Johnson said, "you can start building continents."
SMRTR provides this summary for quick context. The original article belongs to Ars Technica.
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