Group of scientists could experimentally determine the gas composition of the Earth’s atmosphere 4.5 billion years ago. It turned out that in those days the conditions on the surface of our planet were very similar to those of Venus. The planets started in the same way, but evolved into worlds different in terms of surface conditions. Another conclusion of scientists called into question the theory of chemical evolution on Earth. In their opinion, the atmosphere of the young planet lacked sufficient gases for this.
Aerodynamic laser-heated levitation furnace. Image source: IPGP
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Essentially simple experiment required the latest technology. An international team of scientists led by Paolo Sossi, senior researcher at the Swiss Higher Technical School of Zurich (ETH Zurich), reproduced conditions similar to those of the Earth’s surface 4.5 billion years ago in an aerodynamic levitation furnace. For this, a mixture of minerals and metals simulating earth’s magma was heated in a suspended state of the furnace using a laser. The heating temperature reached 2000 ° C, like 4.5 billion years ago on the surface of the magma ocean on our planet.
Scientists could not know for sure what the composition of the atmosphere was then, but in a series of experiments they passed it through a heated oven magma gases with different compositions. The purpose of the experiment is to obtain laboratory samples of the so-called peridotitis (rocks that cooled magma left behind on our Earth). As soon as the laboratory samples of peridotites began to resemble natural samples in composition and, primarily, in the level of iron oxidation in the rock, the experiment could be stopped. This meant that the composition of the gas in the “atmosphere” in the laboratory furnace left the same trace in the artificial rock as the young Earth’s atmosphere in real magma 4.5 billion years ago.
From the results of the experiment, scientists made two main conclusions. First, 4.5 billion years ago, conditions on the surfaces of the Earth and Venus were similar. The pressure of the atmosphere on the surface of the Earth was then a hundred times greater than it is today, and the atmosphere itself was much higher. The main component of the air was carbon dioxide, more oxygen and little water and nitrogen. Venus had similar conditions. But Venus, due to its proximity to the Sun, lost all its water and turned into what we see – a lifeless planet with a toxic atmosphere and extremely harsh surface conditions. But the oceans formed on Earth helped in the absorption of excess carbon dioxide and made it suitable for the emergence of biological life.
Earth 4.5 billion years ago and today as seen by the artist. Image Source: Tobias Stierli / NCCR PlanetS
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The second conclusion of scientists from the experiment is that the popular theory Miller-Urey, which explains the emergence of life on Earth due to the interaction of lightning with certain gases in the atmosphere, in particular, with ammonia and methane, is unlikely, since the atmosphere of the young Earth did not have enough gases necessary for the process. We add, the article has been published and is freely available for reading in the publication Science Advances.
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