How did Earth get its oxygen? Researchers dive for answers in Lake Huron sinkhole.

Doyle Rice, USA TODAY
·2 min read
A scuba diver observes microbes covering rocks in Lake Huron’s Middle Island Sinkhole. Feel like days are just getting longer? They are, and it’s a good thing because we wouldn't have much to breathe if they weren’t, according to a new explanation for how Earth’s oxygen rich atmosphere may have developed because of Earth’s rotation slowing.
A scuba diver observes microbes covering rocks in Lake Huron’s Middle Island Sinkhole. Feel like days are just getting longer? They are, and it’s a good thing because we wouldn't have much to breathe if they weren’t, according to a new explanation for how Earth’s oxygen rich atmosphere may have developed because of Earth’s rotation slowing.

Scientists know that the rise of oxygen on Earth was key to the development of all life on the planet over the past two billion years or so. But how did the oxygen get here?

According to a new study, scientists believe the oxygen increase had to do with longer days as the Earth's rotation slowed down and the amount of daylight increased.

"An enduring question in the Earth sciences has been how did Earth's atmosphere get its oxygen, and what factors controlled when this oxygenation took place," study co-author Gregory Dick, a geomicrobiologist at the University of Michigan's Department of Earth and Environmental Sciences, said in a statement.

"Our research suggests that the rate at which the Earth is spinning – in other words, its day length – may have had an important effect on the pattern and timing of Earth's oxygenation," he said.

The study published Monday in the British journal Nature Geoscience said that longer, continuous daylight kick-started weird bacteria into producing lots of oxygen, making most of Earth's life as we know it possible.

Scientists dredged up bacteria from a deep sinkhole in Lake Huron and tinkered with how much light it got in lab experiments. The water in the there is rich in sulfur and low in oxygen, and the brightly colored bacteria that thrive there are considered good analogs for the single-celled organisms that formed mat-like colonies billions of years ago, carpeting both land and seafloor surfaces.

In a lab, the researchers discovered that the more continuous light the microbes got, the more oxygen they produced.

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The researchers also simulated the gradual slowing of Earth's rotation rate and showed that longer days would have boosted the amount of oxygen released by early bacteria in a manner that helps explain the planet's two great oxygenation events.

Over the millennia, the planet was slowly transformed from one with small amounts of oxygen to present-day atmospheric levels of around 21%.

The study authors and outside scientists said this is just one possible but plausible explanation for Earth’s oxygen increase.

Earth's rotation rate has been slowly decreasing since the planet formed about 4.6 billion years ago due to the relentless tug of the moon's gravity, which creates tidal friction. This gradually lengthened days from six hours to the current 24 hours.

Contributing: The Associated Press

This article originally appeared on USA TODAY: Life on Earth: Did longer days fuel the planet's oxygen growth?