Earth’s transition to permanently hosting an aerobic atmosphere is a disruption process that takes 100 million years longer than previously believed, according to a new study.
When the Earth was first formed 4.5 billion years ago, the atmosphere was almost nonexistent. OxygenBut 2.43 billion years ago, something happened: oxygen levels began to rise, then decline, along with massive climate change, including many glaciers that could cover the entire planet as ice.
The chemical signatures trapped in rocks formed during this era suggest that 2.32 billion years ago oxygen was a permanent feature of the planet̵7;s atmosphere.
But a new study that delves into the past 2.32 billion years ago finds that oxygen levels still date back 2.22 billion years ago, when the planet finally reached its permanent turning point. The new research is published in the journal. nature On March 29, extending what scientists call the Great Oxidation Event 100 million years, it may also confirm a link between oxygen supply and large-scale climate variations.
Related: 10 times the world revealed its weirdness
“We are now starting to see the intricacies of this event,” said co-researcher Andrey Bekker, a geologist at the University of California, Riverside.
The oxygen created in a major oxidation event is caused by marine cyanobacteria, a type of bacteria that produces energy through PhotosynthesisThe main by-product of photosynthesis is oxygen, and eventually the early cyanobacteria churn out enough oxygen to form the planet’s face forever.
The signature of this change is evident in the sedimentary rocks in the sea. In an oxygen-free atmosphere, these rocks contain certain isotopes of sulfur. (Isotopes are elements that have a different number of neutrons in the nucleus.) When oxygen skyrocket, these sulfur isotopes disappear because the chemical reactions they produce do not take place in the presence of oxygen.
Bekker and his colleagues have long studied the nature and disappearance of these sulfur isotopes. They and other researchers have observed that the rise and fall of atmospheric oxygen appears to be traced by three global glaciers that formed between 2.5 billion and 2.2 billion years ago. Surprisingly, the fourth and last glaciers at that time were not linked to swings in atmospheric oxygen levels.
The researchers were puzzled, Bekker told Live Science. “Why do we have four icy events, and three of them can be linked and explained through different forms of atmospheric oxygen?” But the fourth event is free. “
To find out, researchers studied younger rocks from South Africa. These sea rocks cover the next major oxidation after the third ice formation some 2.2 billion years ago.
They found that after the third ice event, the atmosphere was lacking oxygen at first, then the oxygen increased and decreased again. Oxygen increased again 2.32 billion years ago, a point where scientists once thought the increase was permanent. But in a younger stone, Becker and colleagues detected another drop in oxygen levels. This reduction coincides with the final cooling, which has not previously been linked to atmospheric changes.
“This early atmospheric oxygen was very unstable and went up to relatively high levels and dropped to very low levels,” Becker said. “That was something we didn’t expect until maybe in the last four or five years. [of research]. ”
Cyanobacteria and volcanoes
Researchers are still searching for what causes these volatility. But they have some ideas. One important factor is methane, a more efficient greenhouse gas than carbon dioxide.
Today, methane plays a small role in global warming compared to carbon dioxide because methane reacts with oxygen and disappears from the atmosphere in about a decade, with carbon dioxide sticking to it for hundreds of years. But with little or no oxygen in the atmosphere, the methane gas lasts much longer and serves as a more important greenhouse gas.
Thus, this sequence of oxygen supply and climate change is possible, the cyanobacteria begin to produce oxygen, which reacts with methane in the atmosphere at that time, leaving only carbon dioxide. This carbon dioxide was not enough to compensate for the heat effects of the lost methane, so the planet began to cool. Glaciers expanded and the planet’s surface became ice and cold.
Although permanently saving the world from freezing is a volcano under the ice. Eventually, volcanic eruptions caused carbon dioxide levels to rise large enough to warm the world again. And as oxygen production lag behind in ice-covered oceans as cyanobacteria get less sunlight, volcanic methane and microbes start to build up in the atmosphere again, heating things up.
But the carbon dioxide levels from the volcano have another major impact. When carbon dioxide reacts with rainwater, it creates carbonic acid, which dissolves rocks faster than neutral pH rainwater.This faster rock corrosion causes more than 2 thousand more nutrients such as phosphorus to enter the ocean. Millions of years ago, such an influx of nutrients pushed the oxygen-producing marine cyanobacteria into a productive frenzy, increasing oxygen levels in the atmosphere again, driving methane down and starting a cycle. All over again
Eventually, another geological change disrupted this ice-icing cycle.This pattern appeared to have ended about 2.2 billion years ago, when rock records indicated that there was an increase in organic carbon buried, showing that the There is a life that photosynthesis is flourishing. No one knows for sure what motivated this turning point. Bekker and his colleagues hypothesized. The volcanic eruption during this time allowed new nutrients to flow into the ocean, eventually giving the cyanobacteria everything they needed to thrive.At this point, Bekker said oxygen levels were high enough to suppress the influence. The large amount of methane that is permanently on the climate and carbon dioxide from volcanic eruptions and other sources has become an important greenhouse gas in keeping the world warm.
Bekker said there are many other rock sequences from this era around the world, including in West Africa, North America, Brazil, Russia and Ukraine. These ancient rocks need further studies to reveal how the first cycle of oxygen works, especially to understand how the ups and downs affect Earth’s life.
Originally published in Live Science.