Was Venus Once an OCEAN World

Venus may once have looked like Earth — blue skies, liquid water, maybe even oceans.

Today it's the most hostile world in the solar system — 465°C, crushing pressure, skies of sulfuric acid. Yet it sits at the inner edge of the Sun's habitable zone.

For decades, a leading idea held that early Venus had liquid water and a mild climate — until a runaway greenhouse effect took over. As the Sun brightened, the oceans evaporated, the vapor trapped still more heat, and the cycle spiraled until every drop boiled away into space. But that story is now contested: a 2024 study of Venus's atmosphere argues the planet may have been born hot and bone-dry, with oceans that never formed at all.

Whichever turns out to be true, Venus is a warning. It shows how a world in just the right place can still become unlivable — and how thin the line is that keeps Earth habitable.

Follow The Cosmic Vault — the universe is stranger than you think.