Global warming groups falsely claim Venus provides an example of what they call the greenhouse gas effect. According to the greenhouse gas theory, the sun heats the surface of a planet and the atmosphere prevents infrared radiation (IR) from leaving which causes heating. Even if the theory about "trapping" had not been disproved in 1909 by R. W. Wood , the sun cannot be heating the surface of Venus to a temperature of 460 C.
Mercury's surface temperature only reaches 425 C and it is closer to the sun. Mercury's surface doesn't have an atmosphere that reflects 75% of the incoming solar radiation like Venus has. Thus solar radiation cannot be causing the high temperature of Venus. The surface of Venus even receives less solar radiation than earth's surface.
If the sun were heating Venus, there should be a temperature gradient with the highest temperature in the daylight area and the lowest temperature on the night area. Instead the temperature is the same in both areas as well as the same at the poles and the equator.
The only plausible explanation is that there is no significant heat input from outside. The atmosphere of Venus is more likely to be hot because the solid portion of the planet is hot and distributes that heat uniformly to the surface.
One explanation could be that Venus has a greater amount of radioactive material somewhere below its surface. Earth has deposits of uranium, but they are dispersed and produced no real heating of the surrounding material. Venus could have begun with much larger deposits that heated the subsurface areas for a long period of time.
Those who believe in greenhouse gases generally don't understand that earth's surface cools (loses heat) primarily by transferring heat energy to the atmosphere rather than by converting it to radiation. The surface conducts heat to the atmosphere through direct contact with the air.
Bodies of water transfer heat to the atmosphere through the evaporation of water. The ground can also transfer heat energy to the air through evaporation of water. Each gram of water that evaporates takes sufficient heat to reduce the temperature of 540 grams of water by 1 C. This process doesn't necessarily raise the temperature of the atmosphere except that wet air cools slower than dry air.
Greenhouse gas believers tend to ignore the fact that a significant portion of solar energy on earth is stored by plants as the electron bonds holding sugars and other complex carbon molecules together. Plants are not present on Venus to perform this function.
Gravity cools earth's atmosphere. Heat is the kinetic energy or motion of atoms/molecules. Any object attempting to move away from earth's surface whether it's a ball or a water molecule has part of its kinetic energy converted to potential energy. As air molecules move away from the surface they slow down and thus cool. When objects fall back to earth the potential energy is reconverted to kinetic energy, but for air molecules this energy is usually the kinetic energy of the air mass rather than the energy of individual molecules. Only rarely is the potential energy converted to heat energy such as in the Chinook wind along the east slope of the Rockies or the heat bursts associated with the collapse of thunderstorms.
On earth, high air pressure such as a Bermuda High and clouds can prevent heated air from cooling by rising. Venus has clouds that block heated air from rising and air pressure much higher than that of a Bermuda High.
Air doesn't convert heat to radiation very well so it doesn't cool significantly by producing radiation. Radiation by solids depends upon physical characteristics of the material. For example, dark material produces more radiation that light material. Scientists have insufficient data about the surface of Venus to determine how well it converts heat energy to radiation.
A common misconception about heat is that it can be "trapped". That would only be possible if heat were a fluid as Ben Franklin believed. Only heated matter such as gas molecules can be trapped. Greenhouses don't trap heat itself. They trap heated air.
The uniformity of temperature is not the only way Venus differs from other planets. Its rotation on its axis is clockwise which is the reverse of earth and other planets. Other large planets have moons but Venus does not. Venus doesn't have as many impact craters as other bodies including earth's moon. The atmosphere is mostly carbon dioxide instead of an oxygen / nitrogen mix like earth. Venus lacks atmospheric and surface water and its clouds are comprised of sulfuric acid.
All of these conditions could be explained by a single event in the planet's relatively recent past, possibly within the last few hundred million years.
Dr. J Huw Davies of the School of Earth and Ocean Sciences at Cardiff University in the U.K. believes Venus once suffered a head on collision with another large body in its early history. He believes such a collision could have caused Venus to reverse its rotation.
What if such a collision occurred relatively recently and involved a body coming from the direction of the sun on a comet like trajectory? Such a body would have been very hot and moving at high speed to escape the sun's gravitational pull.
To reverse Venus rotation the body would have needed to hit Venus off center and at an angle so that the force would be applied opposite to the Venus direction of rotation.
The body could have been soft if not molten from passing close to the sun. The high speed collision with Venus would have generated heat for the body and Venus.
Instead of a hard impact that might have dislodged a piece of Venus to form a moon (the process many believe produced earth's moon), the body would have spread over the surface of Venus at a high velocity. This process would have filled in low areas while applying a force to the surface to change its direction of rotation. The impact of the flow on indentations such as craters or oceans would have been similar to the impact of water on a water wheel. The flow would have pushed the opposite side of one low area after another in the opposite direction.
A potential problem with reversing Venus' rotation would be the difficulty of changing the direction of rotation of a molten core, in case Venus has a molten core like Earth.
Alternatively, the object might have hit Venus at one of the poles and caused it to turn upside down relative to other planets. The impact wouldn't have changed the direction of rotation of Venus as perceived from the surface of the planet, but the view from other planets would indicate it was rotating clockwise instead of counterclockwise. If you place a transparent clock on a flat surface and then flip it over its hands will appear to someone looking down on it to be moving counterclockwise, but the hands would still be going from 12 to 3 to 6 to 9.
In either type impact, the heat would have incinerated any biosphere Venus might have had as well as igniting methane and similar organic (carbon containing) substances. The fires would have reduced the amount of oxygen while greatly increasing the amount of carbon dioxide.
Underground carbon deposits might have ignited, but burned more slowly because of a shortage of oxygen. The heat could have increased the oxygen supply by breaking down water into hydrogen and oxygen. This process could have continued for a significant period of time helping to keep the subsurface heated.
Methane, coal and wood all burn at temperatures well above the current temperature of Venus.
Any surface and atmospheric water might have "boiled off" into space or broken down by separating the hydrogen and oxygen atoms. The oxygen then would have perpetuated the carbon fires further increasing the amount of CO2 in the atmosphere.
Nils Müller at the Joint Planetary Interior Physics Research Group of the University Münster and DLR Berlin believes infrared radiation from the planet's surface indicates the presence of granite which would imply the planet once had water which combines with basalt to form granite
Underground water could have combined with sulfur compounds to form sulfuric acid. The heat would have allowed the sulfuric acid molecules to rise in the atmosphere to form clouds. Heat could have broken down subsurface water into oxygen and hydrogen with the oxygen then combining with underground carbon through combustion to form carbon dioxide.
Venus deserves more study. The high temperature of the surface would make exploration more difficult because of the need to develop equipment that could function in the heat and not be damaged by the sulfuric acid in the atmosphere. The large amount of carbon dioxide and lack of oxygen could indicate that the planet had large amounts of carbon that could be consistent with some type of biosphere before a major conflagration.