Venus has a surface completely obscured from visible-light view by thick clouds containing sulfuric acid. These clouds form a nearly continuous global layer high in the planet's atmosphere, giving Venus a bright, smooth appearance from space.
The clouds are not made of ordinary water vapor like many clouds on Earth. Sunlight drives chemical reactions in Venus's atmosphere, producing sulfur compounds that combine with water to form sulfuric-acid droplets. The cloud deck reflects much of the sunlight that reaches Venus, while the dense carbon-dioxide atmosphere traps heat below it.
Because the surface cannot be seen directly through the clouds, early astronomers could not determine what Venus looked like underneath. Spacecraft later used radar to map its terrain, revealing volcanoes, vast lava plains, mountains, and impact craters. The clouds also contribute to a common misconception: Venus's bright appearance does not indicate a mild, reflective world; its surface is among the most hostile environments known on a planet.