The deficit of this isotope is now thought to mean that some of the oldest rocks on Earth are actually remnants of our planet’s prototype.

Scientists at MIT and elsewhere have discovered extremely rare remnants of "proto Earth," which formed about 4.5 billion ...

High-resolution isotope data show that a modern-like, oxygen-rich atmosphere was not established until 410 million years ago, supporting a 2-billion-year transitional oxygenation of Earth’s surface.