Billions of years ago, Earth wasn’t blue—it was molten, volcanic, and bone-dry. But as the planet slowly cooled, water vapor from eruptions and space impacts began to condense. And then it rained. Not for days, or months—but for millions of years. 

Scientists believe this relentless downpour helped form Earth’s first oceans. The ground was so hot, much of the early rain evaporated before it could settle, creating a long, steamy cycle of falling and rising water. Eventually, the planet cooled enough to hold the rain—and the oceans were born.