Worlds in Collision
Tim Callahan, religion editor of "Skeptic", presses the case further in claiming that the composition of the atmosphere of Venus is a complete disproof of "Worlds in Collision". "...Velikovsky's hypothesis stands or falls on Venus having a reducing atmosphere made up mainly of hydrocarbons. In fact, the atmosphere of Venus is made up mainly of carbon dioxide—carbon in its "oxidized" form—along with clouds of sulfuric acid. Therefore, it couldn't have carried such an atmosphere with it out of Jupiter and it couldn't be the source of hydrocarbons to react with oxygen in our atmosphere to produce carbohydrates. Velikovsky's hypothesis is falsified by the carbon dioxide atmosphere of Venus."
Atmosphere of Venus
The altitude of the troposphere most similar to Earth is near the tropopause—the boundary between troposphere and mesosphere. It is located slightly above 50 km. According to measurements by the "Magellan" and "Venus Express" probes, the altitude from 52.5 to 54 km has a temperature between 293 K (20 °C) and 310 K (37 °C), and the altitude at 49.5 km above the surface is where the pressure becomes the same as Earth at sea level. As manned ships sent to Venus would be able to compensate for differences in temperature to a certain extent, anywhere from about 50 to 54 km or so above the surface would be the easiest altitude in which to base an exploration or colony, where the temperature would be in the crucial "liquid water" range of 273 K (0 °C) to 323 K (50 °C) and the air pressure the same as habitable regions of Earth. As CO is heavier than air, the colony's air (nitrogen and oxygen) could keep the structure floating at that altitude like a dirigible.