The first oceans
Earth cools enough for rain to stay on the ground, and the planet turns blue.
- When
- Known to
- ± 50 million years
- Era
- Hadean
Once the surface drops below the boiling point, atmospheric steam condenses and falls as rain for what may have been thousands of years, filling the first ocean basins. Zircon oxygen isotopes push the presence of liquid water back to at least 4.4 billion years — far earlier than the name Hadean, coined for a hellish world, implies. Earth may have been temperate and largely ocean-covered for much of this era.