Scientists from Rensselaer Polytechnic Institute have found that the atmosphere of Earth just 500 million years after its creation was not a methane-filled wasteland as previously proposed, stated in a press release from the institute.
Scientists have used the oldest minerals on Earth to reconstruct the atmospheric conditions. The findings, published in the journal Nature, prove that the atmosphere of early Earth was dominated by the oxygen-rich compounds found within our current atmosphere – including water, carbon dioxide, and sulfur dioxide.
“We can now say with some certainty that many scientists studying the origins of life on Earth simply picked the wrong atmosphere,” said Bruce Watson, Professor of Science at Rensselaer Polytechnic Institute. The findings rest on the widely held theory that Earth’s atmosphere was formed by gases released from volcanic activity on its surface. Today, as during the earliest days of the Earth, magma flowing from deep in the Earth contains dissolved gases. When that magma nears the surface, those gases are released into the surrounding air.
“Most scientists would argue that this outgassing from magma was the main input to the atmosphere,” Watson said. “To understand the nature of the atmosphere ‘in the beginning,’ we needed to determine what gas species were in the magmas supplying the atmosphere.”
As magma approaches the Earth’s surface, it either erupts or stalls in the crust, where it interacts with surrounding rocks, cools, and crystallizes into solid rock. These frozen magmas and the elements they contain can be literal milestones in the history of Earth. One important milestone is zircon. The scientists sought to determine the oxidation levels of the magmas that formed ancient zircons to quantify, for the first time ever, how oxidized were the gases being released early in Earth’s history. “By determining the oxidation state of the magmas that created zircon, we could then determine the types of gases that would eventually make their way into the atmosphere,” said Dustin Trail, lead author of the study .
To do this researchers recreated the formation of zircons in the laboratory at different oxidation levels. They literally created lava in the lab. This procedure led to the creation of an oxidation gauge that could then be compared with the natural zircons.
During this process they looked for concentrations of a rare Earth metal called cerium in the zircons. Cerium is an important oxidation gauge because it can be found in two oxidation states, with one more oxidized than the other. The higher the concentrations of the more oxidized type cerium in zircon, the more oxidized the atmosphere likely was after their formation.
The calibrations reveal an atmosphere with an oxidation state closer to present-day conditions.
Source link: https://www.sci.news/geology/early-earth%E2%80%99s-atmosphere-was-similar-to-present-day-one.html
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