Venus is a planet defined by its clouds. The world’s thick, reflective envelope not only whips around the planet at breakneck speeds, but also helps our nearest neighbor shine brighter than any object in the night sky besides the Moon. Unfortunately, these bizarre clouds simultaneously block our view of the venusian surface.

But things weren’t always that way.If you visited the early solar system, Venus and Earth would have seemed to be on similar paths. They were nearly identical in both size and water content. But eventually, Venus lost its oceans. This rapidly transformed the planet into a hellscape filled with volcanoes that belched carbon dioxide — and without oceans, the planet had no way to absorb and store the heat-trapping gas.Scientists know the basics. But despite centuries of study, Venus’ clouds remain shrouded in mystery. Why did Venus lose its water? Is there life in Venus’ clouds? And will humans ever be able to travel there?