The colonization of Venus, Earth's nearest planetary neighbour, has been a subject of much speculation and many works of science fiction since before and after the dawn of spaceflight. With the discovery of Venus' hostile surface environment, attention has largely shifted towards the colonization of the Moon and the colonization of Mars. Recently, however, papers have surfaced on the feasibility of colonizing Venus beginning from the less hostile cloud-tops, making surface exploration in the beginning unnecessary.
Landis has proposed aerostat habitats followed by floating cities, based on the concept that breathable air (21:79 Oxygen-Nitrogen mixture) is a lifting gas in the dense Venusian atmosphere, with about half the lifting power that helium has on Earth. This would allow breathable air domes to lift a colony in addition to their own weight. Alternatively two-part domes could contain a lifting gas like hydrogen or helium (extractable from the atmosphere) to allow a higher mass density.