Earth has hidden bits of its baby self, study shows
MIT researchers just found chemical evidence from proto-Earth—the planet's earliest version from over 4.5 billion years ago—hidden in ancient rocks from Greenland, Canada, and Hawaii.
Their study, published October 14, 2024, in Nature Geoscience, identified a rare deficit of potassium-40 isotopes, offering the first direct evidence that some of Earth's original material survived the massive collision that formed the Moon.
How researchers traced proto-Earth's chemistry
Led by Nicole Nie, the team used advanced mass spectrometry on ancient rocks—including deep mantle material from Hawaii—to catch these unusual potassium signals.
Simulations showed that neither the Moon-forming impact nor later geological changes could explain this chemical "fingerprint," meaning it likely comes straight from proto-Earth.
Plus, these traces don't match any known meteorites, hinting we might be missing some pieces of Earth's building blocks in our space rock collections.
What does this mean for planetary science?
This discovery challenges the old idea that Earth's original chemistry was wiped out by the Moon-forming crash.
Instead, it suggests some of proto-Earth is still buried deep inside our planet—giving scientists new clues about how Earth formed and what it's really made of.