If proto-Earth had all its parts and chemistry replaced to become the Earth we know today, can the two still be considered the same planet? That’s the planetary version of Theseus’s Paradox , an old philosophical puzzle about identity and perception. The popular consensus until recently was that Earth’s chemistry changed completely after a giant meteorite impact, leaving nothing behind from its proto-Earth days.

A new finding suggests that conception may be wrong. In a Nature Geoscience paper published earlier this week, researchers report detecting a chemical signature that appears to have miraculously resisted change for billions of years. Specifically, the team—an international collaboration between the U.S., China, and Switzerland—found an odd imbalance of potassium isotopes in an

See Full Page