Since its formation in 4.5 billion years ago Earth's orbit has been slowly slowing down and its days have gotten longer.Although Earth's slowdown may not be noticeable in human timescales it is enough to make significant changes over the course of eons. New research has shown that the oxygenation of Earth’s atmosphere is responsible for one of the most important changes.Particularly, blue-green algae or cyanobacteria that emerged and proliferated around 2.4 billion years back would have been able produce more oxygen as a metabolic side-product of Earth's longer days.Gregory Dick, a microbiologist at the University of Michigan, stated that "an enduring question in Earth science has been how Earth's atmosphere got its oxygen and what factors controlled when it took place.""Our research suggests the Earth's speed of rotation - or its day length – may have an impact on Earth's oxygenation pattern and timing."Two major parts to this story don't appear to have much in common at first glance. The first is Earth's slowing spin.Earth's spin slows down because of the Moon's gravitational pull. This causes a rotational deceleration as the Moon pulls away slowly.Based on fossil records, we know that 18 hours were the length of a day 1.4 billion years ago. They are also half an hour shorter today than 70 million years ago. Evidence suggests that our world is growing by 1.8 milliseconds per century.The Great Oxidation Event, which is the second component of this event, was when cyanobacteria exploded in such large numbers that oxygen in the atmosphere increased dramatically. Scientists believe that life as we know is impossible without oxidation. So, while cyanobacteria might get a little side-eye, the truth is that we wouldn't have survived without them.We still don't know a lot about this event. This includes the burning question of why it occurred when it did, and not earlier in Earth's History.Scientists working with cyanobacterial microbes were required to make the connections. The Great Oxidation Event was caused by cyanobacteria.The lakebed is home to purple cyanobacteria, which produce oxygen through photosynthesis, and white microbes, which metabolize sulfur. The white microbes, which metabolize sulfur, rise to the top and munch their way through the microbial mat at night. The white microbes disappear when day breaks and the Sun rises sufficiently high in the sky.Geomicrobiologist Judith Klatt, of the Max Planck Institute for Marine Microbiology in Germany, stated that "now they can start photosynthesize to produce oxygen."However, they take a while to get started and there is a long wait for the morning. It seems that cyanobacteria rise later than people who are awake in the morning.This means that the time window in which cyanobacteria can produce oxygen is extremely limited. Brian Arbic, an oceanographer at the University of Michigan, was intrigued by this fact. He wondered if the Earth's past changes in day length had affected photosynthesis.Klatt stated that it is possible that similar competition among microbes caused the delaying of oxygen production on the Earth's early days.The team conducted experiments and measured the microbes in both their natural environment as well as in a laboratory to prove this hypothesis. Based on their findings, they also did detailed modeling studies to model microbial oxygen production and Earth's history."Intuition suggests two 12-hour days should be comparable to one 24-hour. Arjun Chennu, a marine scientist at the Leibniz Centre for Tropical Marine Research (Germany), explained that the sun rises and sets twice as fast and that oxygen production follows closely."But, the release of oxygen by bacterial mats doesn't because it is restricted by molecular diffusion speed. This subtle uncoupling of oxygen released from sunlight is the core of the mechanism.These results were then incorporated into global models for oxygen levels. The team discovered that the lengthening of days was linked to an increase in Earth's Oxygen - not just during the Great Oxidation Event but also another atmospheric oxygenation, the Neoproterozoic Oxygenation Event which occurred around 550 to 800 millions years ago."We connect laws of physics operating on vastly different scales from molecular diffusion and planetary mechanics. Chennu stated that Chennu has shown that there is a fundamental connection between day length and the amount of oxygen ground-dwelling microbes can release.It's quite exciting. This is how we link the dance between the molecules in our microbial mat and the dance of our planet's Moon.Nature Geoscience published the research.
