Introductory text to the planet Venus
The Venus is one of the four rock planets of the solar system and after Mercury the second closest planet to the sun. Mass, gravity and size of Venus are close to Earth, which is why astrologers sometimes refer to Venus as 'planetary twin' of Earth. In the sky, Venus is often seen in the morning or evening even with the naked eye. Only sun and moon shine even brighter.
If you observe Venus with a high-resolution telescope, you will soon discover that the surface of the planet is hidden under a cloud layer. The clouds have a diameter of at least 15 kilometers, consist mainly of sulfuric acid and permanently cover the planet. Because as soon as rain sets in and falls in the direction of the surface, all the liquids evaporate just below the cloud cover due to the high soil temperatures and rise again as steam.
The Venus - Hottest Planet of the Solar System
Although Venus is not the closest planet to our sun, here are the highest temperatures in the solar system (excluding the sun itself). The thick cloud layer is responsible for this. When sunrays hit the cloud cover of Venus, around 75% of the rays are initially reflected back into space. No other planet has such a high retroreflective value. In this context one speaks of the albedo. By comparison, the earth has an albedo of 0.3 - thus reflecting 30% of the sun's rays immediately. This measure of reflection can be experienced in the summer. Black T-shirts heat up a lot faster than white T-shirts. Dark surfaces absorb light, bright surfaces reflect light. The bright clouds of Venus reflect the light. But the high albedo speaks once against the hot temperatures on Venus.
The atmosphere of Venus consists of 97% carbon dioxide, a greenhouse gas. The proportion of the sun's rays, which penetrates the cloud layer, radiates onto the surface and heats it up. The heat radiation rises and would normally radiate slowly back into space. Greenhouse gases can store the emitted heat radiation and release it back to the environment, which causes it to heat up as well. The greenhouse effect on Venus is so strong that temperatures rise up to 500 ° C.
Facts about Venus
Although the mass and size of Venus are close to Earth, there are some significant differences. Venus is the planet with the lowest rotation speed in the solar system. So a Venus day, ergo a complete rotation around its own axis, takes 243 days. The year of Venus, thus a full orbit around the Sun, lasts only 225 days in comparison. The winds on the planet are moving much faster. At wind speeds of 400km / h, the wind only needs 100 hours to orbit the Venus once.
With modern radar equipment, it was only in the late 20th century that it was possible to see the cloud cover of Venus. So far, one could only speculate what was under the clouds. For a long time, not a few hoped that simple life would have arisen on Venus, including optimistic scenarios of a green and living planet. Instead, the spacecraft provided the image of a volcanic-dominated Venus with a relatively low number of meteorite craters. Temperature fluctuations on recently taken infrared images (year: 2015) also indicate volcanic activity. That explains at least the comparatively small number of impact craters. In addition, the dense atmosphere prevents smaller meteorites from striking Venus.
Colonization of Venus possible?
In the '60s and' 70s, thoughts of a colonization of Venus regularly appeared as near-Earth 'planetary twin'. The problem is not only the adverse conditions, such as the lack of water, the absence of oxygen in the atmosphere or the temperatures of + 500 ° C. The air pressure on Venus is - for us hostile - 90 bar. With the enormous air pressure already sent by the US and the Soviet Union space probes had their problems. At the pioneering age of aerospace, most probes survived only a few seconds to minutes on the Venus surface. Be it by the air pressure, the heat or the sulfuric acid in the atmosphere. In view of this, the term 'planetary twin' seems at best to apply to mass and size. All other conditions, especially those concerning a life on Venus, are classified as life-threatening.