A recently published article tries to solve the dilemma of alien life. As scientists approximated there may be hundreds of billions of other planets in our galaxy, the chances are that many of them could be inhabited. The only major setback would be their low survival rate.
The violence and instability surrounding the formation of planets composed out of rocks led scientists to believe that alien life would have a tough time surviving the events.
One hypothesis is that fossil microbes could be found on the surface of the alien planets. Taking into consideration the fact that missions only take remote samplings from the atmosphere, the scientists’ chances to find fossilized alien bacteria are very small.
The study tries to sustain the idea that early extinction is the main danger to life in the universe. The authors came up with a new model which attempts to explain why space exploration missions have not yet found any signs of alien life.
The model is called “Gaian Bottleneck” and focuses on a truism: a planet needs to be inhabited in order to remain habitable. Even though life may emerge on alien worlds, its persistence is not thought to be common.
Scientists believe that rock planets were more similar one to another in the early years of the galaxy. The asteroid bombardment might have brought life on other planets too, just as it presumably brought life to Earth.
However, over billions of years, planets took a different course. Venus, for example, was subject to runaway heating. On the other hand, Mars experienced cooling. Both events could cause life extinction.
Other factors that may have prevented life on other planets is the variations in water and greenhouse gases, both of which inducing destructive conditions. Researchers also presume that the weathering cycle present now on Earth was inoperative 3 billion years ago.
Scientists believe that the presence of microbe communities may have triggered the weathering cycle. Therefore, the apparition of life on Earth may have been self-sustained and in continuous evolution.
Life persistence on Earth is explained by the fact that the early metabolisms were to ones to create the greenhouse gas composition of the atmosphere. The same substances that are involved in metabolic reactions are also greenhouse gases constituents: hydrogen, water, methane and carbon dioxide.
These conditions were not sufficiently met by other rock planets. Scientists believe that, even if life could have emerged on alien planets, its survival rate must have been too low. With no biological premises to create a habitable environment, life would have gone extinct on these other similar to Earth planets.
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