Before the Great Oxygenation Earth Didn’t Have “Breathes of Oxygen”

When did oxygen first appear in Earth’s atmosphere? The answer to this important question has evolved over the years. And today, once again, researchers are providing new answers. According to them, it would not have existed significantly before the Great Oxygenation episode 2.3 billion years ago.

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It would be difficult for humans and animals to survive without the oxygen generated by plants. This gas is the result of a chemical reaction called photosynthesis, which takes place in the heart of these plants. During this episode of Cazaco, UNICEL and the University of Lille 1 explain to us how this reaction occurs.

Our Earth was formed 4.5 billion years ago. And scientists have long believed that oxygen in it did not appear significantly Atmosphere Before the Period They Call the Great Oxygenation – Anything Speak great oxidation Or the oxygen disaster. About 2.3 billion years ago. in question, cyanobacteria Who must have started consuming carbon dioxide (CO.)2) while producing oxygen (O.)2) Beginning of Photosynthesis,

But already about 15 years ago, some work suggested that the presence of oxygen in Earth’s atmosphere may be even older than that. Go back at least 3 billion years. momentarily. who are the researchers “Breathe of Oxygen”,

Today, University of Michigan researchers (United States) come to undermine this hypothesis “Breathe of Oxygen” Before the Great Oxygenation. According to him, the samples analyzed at that time may also contain Minerals formed after their admission. Small signs mixed in with old signs. A story that is complicated to entangle and is likely to distort interpretations.

In 2007, researchers actually worked on shale samples collected, among other things, on Mount MacRae (Australia). They did chemical analysis on these pulverized rocks and found evidence of oxidation and reduction. molybdenum And you sulfur, The new functions are based on high technology Resolution, of which, fluorescence spectroscopy of X-ray,

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Ensure correct interpretation of chemical signatures

The use of this type of method has enabled researchers to assign a relative timetable to the processes that led to the formation of shale, This specifically shows that the molybdenum identified comes from volcanoes. It is believed to have actually been concentrated in the cliffs of Mount MacRae. “Breathe of Oxygen”, then turns physical and chemical Changed sediment in the rocks. In the process, pathways have opened up allowing many fluids to transmit oxidation signals that are actually believed to date back hundreds of millions of years. “Breathe of Oxygen”,

The work of University of Michigan researchers therefore provides an alternative explanation for the composition of the Mount MacRae Shales. They also confirm that atmospheric oxygen level Before the Great Oxygenation there was little. it can also be called “negligible” In a period of about 150 million years before this abrupt change.

results that thus call into questionEarly existence of cyanobacteria, Rather, they support the hypothesis that oxygen-generating photosynthesis evolved shortly before the great oxygenation event. And besides being of interest to scientists studying Earth, they may also attract the attention of those who investigate other planets. There should no doubt come a general reflection on how the chemical signatures of billions of years old rocks should be analyzed and interpreted.

Oxygen enriched atmosphere more quickly than expected

Two billion years ago, there was a rapid increase in the level of oxygen in the atmosphere. Photosynthetic organisms are blamed for this massive pollution. But it must have started millions of years ago, which complicates the explanation and plays a role in geological events.

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article by Jean-Luc Gaudet Published on 09/28/2007

, We thought these scans were going to be boring » admits Gail Arnold, one of the scientists participating in this work, which may have seemed tedious indeed. During the summer of 2004, section a. A team was constituted to study the section by Carrot 908 m long from a borehole in rocks in the Hammersley region of Western Australia. The researchers were particularly interested in the molybdenum content, rhenium etcetera uranium, The amount of these three elements in the sediment is highly dependent on the amount of oxygen in the environment.

The researchers did not expect any surprises in this routine work. Error. By attacking carrots at levels consistent with the Late Archean, about 2.5 billion years before present, American scientists were surprised to find the oxygen content much higher than expected. At the time, in fact, it was believed that Earth’s atmosphere was still very poor in oxygen, as it has always been since the beginning of Earth’s history 4.56 billion years ago. We know that suddenly, between 2.4 and 2.3 billion years ago, the concentration of oxygen rapidly increased, reaching 21% of the present day. This ” great oxidation “or the “oxygen disaster”, to use expressions in the experiment, was probably caused by cyanobacteria, which were the first organisms to attract energy From Light solar through photosynthesis.

by recovering carbon from gas Carbonic, these tiny organisms produced a terrible pollutant, oxygen, that caused carnage in living beings. The cyanobacteria themselves were probably struggling to cope molecule Chemically aggressive. The fact that they succeeded already suggested that they may have been able to optimize it before.

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Volcanoes and creatures, these big pollutants

Late last year, researchers estimated thathydrogen (h)22Ioxygenated water) could have been produced in large quantities during one episode of glaciation Global Earth (a phenomenon known as a “snowball”). stop the maintenance of a ozone layer, this coolness must have released the rays ultraviolet Upon hitting the Earth’s surface, the water was released into the atmosphere, turning it into hydrogen peroxide. Thus the cyanobacteria would have learned slowly and quickly to defend themselves against an oxidizing environment.

The Australian carrot tells a different story: Oxygen has already skyrocketed in the atmosphere – the authors speak of oxygen breathing – 50 to 100 million years before the Great Oxidation. Why ? The question remains open. Some had already imagined that photosynthetic organisms would have started producing oxygen before the great oxidation. Others confirm this, saying that geological phenomena (interactions with gases emitted by) Volcano very active) destroyed this oxygen (these are of course geologists,

In the end, we realize that we still have very little understanding of this extraordinary event that breathed so much oxygen into the atmosphere and we don’t know how to explain why this rate is 21% with such a beautiful accuracy. But why did it stand still? The conclusion is that a better understanding of the interactions between geological and biological phenomena remains to be done. To tell the story of Earth, scientists will no doubt need a little more multidisciplinaryness…

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