Earth’s atmosphere 4.5 billion years ago was similar to Venus’ current toxic atmosphere, scientists reveal

The scientific community was able to reach a consensus on what the surface of the Earth could look like 4.5 billion years ago, covered with hot molten magma. But the corresponding atmosphere remained unclear. Now, researchers say Earth’s atmosphere billions of years in the past was very similar to Venus’s current atmosphere.

In a new study, an international team of scientists attempted to collect what Earth’s atmosphere might have been several years ago by creating magma in the laboratory and exposing it to a varied mixture of gases. The results led the authors to infer that 4.5 billion years ago, Earth’s atmosphere would have been similar to that of present-day Venus, which is toxic and unable to sustain life.

Magma creation in a laboratory

Unlike the lush, blue planet we know today, Earth, billions of years ago, our planet was characterized by volcanoes, volcanic eruptions, and rivers of magma flowing across the surface. “Four and a half billion years ago, magma was constantly exchanging gas with the atmosphere above. The air and magma influenced each other. So, you can learn from each other,” said Paolo Sossi, lead author of the study, in a statement.

To ascertain what Earth’s primordial atmosphere might have been, the authors created magma in the laboratory. They achieved this by mixing powders that helped to arrive at a composition similar to that of the Earth’s molten mantle (the layer between the crust and the inner core). This mixture was heated to produce magma.

However, what seems simple required advanced technology to accomplish. “The composition of our mantle-like powder made it difficult to melt – we needed very high temperatures of around 2,000 ° Celsius,” Sossi said.

Modern technology to recreate the past

To produce the magma, the scientists used a special furnace that used a laser for heating. The magma was levitated inside the furnace by introducing streams of gas mixtures that flowed around it. The mixtures used were a plausible composition of gases that could have interacted with magma 4.5 billion years ago. With each different mixture, the magma sample was affected differently. Thus, the various forms of magma were obtained.

The oxidation of iron (or rust) when it comes into contact with oxygen is a known phenomenon. The rocks derived from the mantle contain iron in them. When the gas mixture the scientists blew on their magma contained a lot of oxygen, the iron inside the magma oxidized more. “The key difference we were looking for was the oxidation of the iron contained in the magma,” Sossi noted.

According to Sossi, the level of oxidation of iron found in cooled magma samples could be compared to peridotites, naturally occurring rocks that make up the Earth’s mantle today. The oxidation levels within these rocks continue to maintain the influence of the ancient Earth’s atmosphere. Therefore, a comparison of laboratory-produced and natural peridotites provided vital clues as to the closest combination to our planet’s prehistoric atmosphere.

More like Venus and less like Earth

Sossi said: “What we found is that, after cooling from the magmatic state, the young Earth had a slightly oxidizing atmosphere, with carbon dioxide as the main constituent, as well as nitrogen and some water.” He added that, a hundred times that of today, the surface pressure was also significantly higher. Due to the hot surface, the atmosphere was also much higher. These attributes suggest that the atmosphere of ancient Earth was similar to that of present-day Venus.

The results of the study led the team to draw two key conclusions. First, Venus and the Earth started with a similar atmosphere. Due to its proximity to the Sun and the resulting higher temperatures, Venus has been deprived of most of its water. However, the Earth retained its water, mostly in the form of oceans, which absorbed most of the CO2 in the air. This led to a significant reduction in the gas level.

Second, a widely popular theory explaining the emergence of life has lost its likelihood. Known as the so-called “Miller-Urey experiment”, it claims that a lightning strike reacts with certain gases, particularly methane and ammonia, resulting in the creation of life’s building blocks, amino acids. However, this event would have been highly unlikely as the necessary gases were not available in the necessary quantities.