Translation. Region: Russian Federal
Source: People's Republic of China in Russian – People's Republic of China in Russian –
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Source: People's Republic of China – State Council News
BEIJING, Sept. 9 (Xinhua) — Chinese scientists have found that Earth's atmosphere has experienced three major oxygen transitions over the past 2 billion years, moving from anoxic to oxygen-abundant, providing new insights into the origins of life, evolution and long-term biohabitability of the planet.
The study, conducted by scientists from Chengdu Institute of Technology and Nanjing University, was recently published in the journal Nature. It presents data on triple oxygen isotopes in sulfate salts found in sedimentary rocks.
"Our study provides the first direct evidence to date that oxygen levels on Earth reached their current levels around 410 million years ago, confirming a three-stage process by which our planet's surface was saturated with this life-giving gas," said Li Chao, a professor at the Institute of Sedimentary Geology at Chengdu University of Technology.
He explained that triple oxygen isotopes refer to the three stable isotopes of oxygen, and their relative abundance in various natural substances was not constant, but underwent subtle changes due to biogeochemical processes in the atmosphere and oceans. By measuring these subtle differences – much like reading the Earth’s “fingerprint” – scientists can infer how ancient environments on our planet’s surface evolved.
However, researchers have long lacked effective tracking methods and data that can summarize changes in Earth’s surface oxygen supply, its sources and sinks, and key controlling factors. This study addresses this gap by combining systematic sample analysis and the integration of documentary data.
New data show that the first sudden increase in oxygen content occurred in the Paleoproterozoic era /2.4-2.1 billion years ago/, the second in the Neoproterozoic era /about 1 billion years ago/, and the third in the Paleozoic era /about 440 million years ago/.
These changes indicate that oxygen levels on Earth gradually increased from low levels, approaching the current oxygen-rich stable state about 410 million years ago, and this process continued for almost 2 billion years.
Meanwhile, during the Neoproterozoic, dramatic, interconnected shifts in carbon, sulfur, and oxygen isotopes suggest that as atmospheric oxygen increased, it began to periodically acidify the largely oxygen-poor oceans.
"This study not only lays a solid foundation for understanding the stepwise evolution of complex eukaryotic life, but also opens up new perspectives for studying the formation of habitable planets and ancient hydrocarbon source rocks," Li Chao said.
“It also demonstrates the interactive relationship between the atmosphere and the oceans throughout this long process, providing the basis for a crucial step in answering the fundamental question of when and how the Earth became habitable,” he concluded. -0-
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