For 150 million years before the “revolution”, which finally filled the atmosphere with oxygen, the planet experienced another such catastrophe that ended in a few million years.
Ancient rocks of about 2.45 billion years old contain traces of an oxygen disaster – global climate change. It is believed that they are associated with the emergence of photosynthesis, which led to the appearance of free oxygen, which changed the face of the planet. However, hundreds of billions of years before this event, the level of oxygen on Earth was already rising – and fell again. This group of professor at the University of Washington Roger Buick (Roger Buick) wrote in an article published in the journal PNAS.
“The process of formation and decay of oxygen molecules in the ocean and the atmosphere for a long time was like a war without an obvious winner, down to an oxygen disaster,” says one of the authors of the work, Matt Koehler. “These intermediate catastrophes were like battles in the war, and gradually the balance shifted towards oxygenation.” In fact, back in 2007, Roger Buick and colleagues showed that sedimentary rocks on the shelf of Western Australia contain traces of an “intermediate oxygen disaster” that occurred 50 million years before the main one.
In his new work, the team of Professor Buick describes another such event, dated 100 million more years before – about 2.66 billion years ago – and come to naught for several tens of millions of years. This was indicated by an analysis of the isotopes of nitrogen and selenium contained in the rocks of the Jeerinah formation in the same Western Australia. The cores extracted from the shallow bottom show gradual changes in the content of these elements and their return back – changes associated with the appearance and disappearance of oxygen.
The fact is that the exact isotope composition of nitrogen atoms in ancient sediments depends on the activity of microorganisms that can use it for the synthesis of nitrates, and nitrates for the production of energy. This process requires free oxygen, so that nitrogen is able to say about its presence in the surface layers of the ocean. Selenium is also found in sulfurous minerals of the land, and the increase in oxygen in the atmosphere leads to their oxidation and washing out of selenium in the sea, where it accumulates the more, the more oxygen in the air.
“If you can not detect oxygen in the atmosphere of a distant planet, this does not mean that there is no life or even photosynthetic life on it,” adds Roger Buick. “Perhaps life simply has not become a powerful enough source of free oxygen, capable of for a long time” overcoming “the mechanisms of its binding.”
