With life on the planets neighboring with the Earth, everything has been very difficult for a long time. On Mars, more than three billion years ago, rivers still flowed, in which, theoretically, something living could exist. If bacteria already lived on Earth at that time, traces of which paleobiologists find in different parts of the globe, so why not something to live on Mars during this period? True, then Mars lost its water, and now not only life, but even its traces still cannot find the rovers roaming the Martian wastelands.
On Venus, the situation is even worse. If it is very cold on the Red Planet now, then on the surface of Venus, on the contrary, it is too hot. So much so that liquid water cannot be there by definition. Therefore, astrobiologists, who do not want to delete the planet from the list of potentially inhabited worlds ahead of time, are looking for where this life could take refuge. This is how the hypothesis of microorganisms that live and reproduce high in the Venusian clouds appeared. This bold theory is confirmed from time to time, and also lost from time to time.
But all these castles in the air, inhabited by bacteria, could arise only if liquid water existed on Venus for a long time in the form of an ocean, lakes, or something else. At least, scientists have not yet found a more favorable place for the origin of life. Then, appearing in liquid water, life could then “fly away” to heaven, when it became completely unbearable on the surface of the planet.
However, as they write in Nature researchers from the University of Geneva and the National Research Center in Switzerland, Venusian life could not fly away. More precisely, nowhere. Because according to the climate model they built for the early evolution of the planet’s atmosphere, its surface did not cool down enough for water to condense on it. This means that there was no big ocean, no modest lake, no life.
When the Earth and Venus were just formed, their surfaces were an ocean of hot magma, and almost all the water that was only was in the form of vapor along with other gases in the atmosphere. The surface of the planets gradually cooled down, but the whole question is – to what temperature? And to find out, you need to look at what helps the planet to cool down, and what prevents it.
The main heating pad for the planet’s surface is the Sun. The closer the planet is to the Sun, the more energy it receives from it. Venus in this sense was unlucky, it turned out to be closer to the Sun than the Earth. The second point to consider is the activity of the Sun itself. In the early stages, it did not shine as brightly as in later stages, as if giving young planets some “breathing space” to cool down faster.
But the planet’s own “blanket” – the atmosphere – also prevents the planet from cooling down. If it is dense and contains a lot of greenhouse gases, for example, the same water vapor, then a significant part of the heat emitted by the surface does not fly into space, but is retained by clouds and returns back. This is exactly what happened on young Venus: according to the constructed climatic model, dense clouds formed mainly on the side of the planet that was not illuminated by the Sun, preventing it from cooling down at night. And in the daytime, this surface was already heated by the sun’s rays.
While the young Sun was not shining at full power, the Earth, located a little further from it, “managed” to cool down and condense most of the water vapor in the form of an ocean, thereby killing two birds with one stone: creating a reservoir for future life and reducing the greenhouse effect. And Venus did not have time. The sun warmed it up a little more, it cooled down a little more slowly and it didn’t come to liquid water. And when the brightness of the Sun increased, it was already too late. If the Earth were closer to the Sun, if the young Sun were a little brighter, then our planet had every chance to repeat the fate of Venus and turn into a steam boiler without a lid. And without life, of course.
Source: Автономная некоммерческая организация "Редакция журнала «Наука и жизнь»" by www.nkj.ru.
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