If we couldn’t see Venus, we’d hardly dare to imagine such a deceptive world.

Named for the Roman goddess of love and fertility, the planet is one of the nighttime sky’s most beautiful sights. But up close, Venus smells like rotting eggs. Its raindrops would dissolve flesh, and at its surface, temperatures are hot enough that wood and gasoline would spontaneously burst into flame, while the pressure is so high that submarines would crumple.

Though today’s Venus is grotesque, scientists suspect it was once quite different—temperate, perhaps awash in oceans, maybe even inhabited. For billions of years, our solar system may have been home to two blue marbles orbiting the sun, side by side. Yet while