Earth days used to be just six hours, and complex life was only possible when it started to slow down, scientists have found.
The shorter days are the product of the moon’s gravitational pull on Earth, which is much stronger than it is today, causing it to spin faster on its axis. Over time, friction has slowed the earth and one revolution now takes less than 24 hours.
“When the Earth-Moon system emerged, the days were much shorter, maybe even six hours,” said Dr. Brian Arbic, a physical oceanographer at the University of Michigan.
But at that time, some 2.4 billion years ago, conditions on Earth were inhospitable and it was impossible for the emerging microbial life to survive. As the earth began to spin more slowly, microbes called cyanobacteria – also called blue-green algae – thrived, which were able to use sunlight to generate energy and release oxygen.
This process of photosynthesis sustains all life on earth today, and the success of primitive algae thousands of years ago means oxygen has increased from a negligible level to one in five molecules in the air today – enough for marine and land fauna to reproduce and flora.
dr. Arbic studied the interactions between two types of microbes in deoxygenated waters at the bottom of Lake Huron in Michigan to understand how the algae began to produce oxygen.
At the disposal pit there are mats made of two types of microbes – cyanobacteria and sulfur -eating bacteria – that live side by side. During the day oxygen -forming algae dominate and rise, at night sulfur -eating bacteria take over.
The researchers write in their study published in Nature Geoscience that a similar symbiotic relationship may have existed in Earth’s early years.
“However, it takes several hours before they actually work,” said Judith Klatt, a geomicrobiologist. “Cyanobacteria are more like late risers than early morning people, it seems.”
He believes that shorter days may be more suitable for cyanobacteria than other life forms, so that they can thrive and oxygen production models could serve as templates for future life forms.
“On short days, there is less time for gradient development and thus less oxygen can escape the mat,” Klatt said.
Arjun Chennu, a marine microbiologist, said, “Intuition shows that two 12-hour days should equal one 24-hour day. Sunlight rises and falls twice as fast, and oxygen production follows suit.
“But not the release of oxygen from the bacterial mat because it is limited by the speed of molecular diffusion. This subtle separation of the release of oxygen from sunlight is at the heart of this mechanism.”
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