Without the Sun there is no life: scientists start from this overwhelming truth to understand the origins of the biosphere. Among the main mysteries of science is the correlation between the Earth and the only star in our planetary system.
When life was just emerging on our planet, about 3.8 billion years ago, the Sun was very young, therefore it radiated 70% of the energy that we receive today. It is difficult to imagine, under these conditions, a planet surrounded by oceans. To maintain the liquid state of water, high temperatures on Earth were essential. It should be noted that there are no signs of glaciation that show that the planet has been frozen at the beginning of life. So how to explain this contradiction?
In 1972, astronomers Carl Sagan and George Mullen elaborated the “paradox of the young and weak Sun”, and since then they have tried to solve this enigmatic fact. Often, the paradox is explained by astrophysical factors or by the atmospheric composition of the Archaic Earth.
When the atmosphere was formed, it is possible that there were higher concentrations of greenhouse gases. Science has focused more on this theory. Gases as powerful as carbon dioxide (CO2) and methane (CH4) could have contributed to the increase in temperature on the planet during the Archaic eon, that is, in the time from 4,000 million years to 2,500 million years. years of antiguaty.
The recent study by researchers from the University of Vienna and the Austrian Academy of Sciences, supports the maintenance of liquid water by the high content of carbon dioxide and nitrogen (N2) in the atmosphere of the Archaic Earth.
They were based on the analysis of the effects of different CO2 / N2 mixing ratios and levels of solar activity in the atmospheric exhaust, as they explain. They conclude that to counteract the ultraviolet rays from the Sun, the minimum percentage of greenhouse gases was around 40%, according to their calculations, and this composition was what allowed to preserve the necessary temperature for the existence of liquid water.
Is the scientific enigma of the weak and young sun solved? There are other theories that could support the thermal equilibrium necessary for life, such as the production of a non-biological carbon cycle during the formation of the continents. Or the relationship with the moon, which was much closer at that time: the great gravitational interaction could have released heat by the force of the tide.