Around 2.4 billion years ago, the Earth’s rotation decreased, which may have led to the rise of oxygen flow on our planet and aided the survival of life.

The Earth’s rotation time, according to a new study published by University of Michigan, may have been approximately six hours when it was four billion years old, but it eventually slowed down to the 24 hours we observe currently.

Around 2.4 billion years ago, the study says, there was so little oxygen in the atmosphere of Earth that no living species could survive. Microbes breathed carbon dioxide, while cyanobacteria created oxygen, making photosynthesis (The process by which plants, algae and bacteria use sunlight, water, and carbon dioxide to create oxygen and energy) one of the oldest forms of life.

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However, the Earth’s atmosphere dropped to a tenth of its current level of oxygen in about 400 million years. This increase in oxygen allowed animals and plants to evolve, and more plants began to produce oxygen as a result.

To find out more about the oxygen burst, researchers investigated the Middle Island Sinkhole in Lake Huron. A layer of 400 million-year-old limestone, dolomite, and gypsum bedrock covers the waterbody, which developed from the saltwater oceans that previously dotted the continent. Adding to this are purple-oxygen-producing cyanobacteria that make oxygen through photosynthesis.

However, during the day and nighttime, other white sulfur-oxidizing bacteria cover cyanobacteria, blocking sunlight it needs for photosynthesis. But when the amount of sunlight reaches a critical level, the white sulfur-oxidizing bacteria is pushed below the cyanobacteria, thereby allowing direct sunlight for the latter to create oxygen.

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Explaining the phenomenon, Judith Klatt of the Max Planck Institute for Marine Microbiology says, “Two groups of microbes in the Middle Island Sinkhole mats compete for the uppermost position, with sulfur-oxidizing bacteria sometimes shading the photosynthetically active cyanobacteria.”

“It’s possible that a similar type of competition between microbes contributed to the delay in oxygen production on the early Earth,” the author adds.

University of Michigan geomicrobiologist Gregory Dick explains the logic behind the phenomenon.

“The idea is that with a shorter day length and shorter window for high-light conditions in the afternoon, those white sulfur-eating bacteria would be on top of the photosynthetic bacteria for larger portions of the day, limiting oxygen production,” he says.