Research

Why did an oxygen catastrophe occur on Earth and how did the Moon affect it

Lots of oxygen in our atmosphereplanets did not appear immediately. Before it appeared, organisms lived in the oceans that did not need oxygen. Microbes were able to synthesize organic molecules, using the energy of the sun for this. Simply put, they were capable of photosynthesis, but no oxygen was released. The situation changed 3.5 billion years ago, when cyanobacteria capable of oxygen photosynthesis arose. True, in sufficient quantities, the gas necessary for our life did not appear on the planet immediately, but after about one billion years. As a result, bacteria accustomed to an oxygen-free environment died out or went to the depths of the oceans, and new organisms took their place. But why did it take a billion years for oxygen to appear? Scientists say that the Earth would have needed even longer if not for one event that helped cyanobacteria change the atmosphere and radically affect life on the planet.

On Earth 3.5 billion years ago, when the day lasted 6 hours, there was no oxygen in the atmosphere

Oxygen in the earth's atmosphere - what accelerated its appearance?

The level of oxygen on Earth has been risingevenly, but stepwise, that is, at some moments, the rate of saturation of the atmosphere with it increased. Hence the assumption arose that something contributed to this process.

A group of scientists led by Judith Klatt fromThe Max Planck Institute for Marine Microbiology has put forward an interesting explanation for what happened on the planet several billion years ago. According to scientists, microorganisms were able to release more oxygen into the atmosphere as a result of the increase in daylight hours. In those distant times, the Earth rotated much faster than it does now. Therefore, the duration of the day was shorter - about 6 hours. Accordingly, daylight hours lasted only a few hours.

This raises the question, what is the difference between the distinguishingoxygen to bacteria - a long day on Earth and a long night or a short day and a short night? After all, the amount of incoming sunlight on the earth has not changed. But, as it turns out, there is a difference.

The saturation of the atmosphere with oxygen accelerated due to the slowdown in the speed of the earth's rotation

How the length of the day affected the oxygen in the atmosphere

Judith Klatt with a group of researchers fromUniversity of Michigan studied water in a sinkhole on Middle Island (an island on Lake Huron). Groundwater seeps into it from the bottom, while the level of oxygen content is extremely low. In other words, the conditions are similar to those that were on our planet for billions of years before the appearance of oxygen in the atmosphere.

There are mainly two types of microbes that live in water -purple cyanobacteria that produce oxygen; and white sulfur-oxidizing bacteria. The first generate energy with the help of sunlight, the second - with the help of sulfur. To survive, these bacteria perform a kind of “dance” every day.

Almost all of the oxygen in the atmosphere comes from cyanobacteria.

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From dusk to dawn, sulfur-eating bacterialocated on the surface, that is, above the cyanobacteria, blocking their access to sunlight. When the sun comes out in the morning, sulfur eaters move down and cyanobacteria rise to the surface to start photosynthesis and produce oxygen. However, from the moment the sun rises until the process of photosynthesis begins, several hours pass. That is, it turned out that cyanobacteria like to “get up late”. In this case, the length of daylight directly affects the amount of oxygen produced by bacteria.

Why did the Earth's rotation slow down?

The earth 3.5 billion years ago rotated with incrediblehigh speed, but the situation changed with the appearance of the moon. Gravity began to act on the Earth. In addition, tides arose and ebb, which also contributed to the slowing down of the planet's rotation.

We owe the appearance of modern life on the planet to the moon

The first strong deceleration of the Earth occurred on 2.5billion years ago, and it just coincides with the period when the oxygen content in the atmosphere greatly increased. As a result, the so-called “oxygen catastrophe” occurred. Then the slowdown of rotation stopped for about one billion years. This coincided with a period when there was no acceleration in the rise in the level of oxygen in the atmosphere. About 600 million years ago, the planet's rotation slowed down again, and during this period of time there is also a jump in oxygen levels. By the way, the speed of rotation of our planet is unstable to this day. For example, in 2020, its acceleration was noted.

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Comparing the pattern of slowing down the rotation of the earth andsaturation of the atmosphere with oxygen, scientists came to the conclusion that there is a relationship between these processes. The aforementioned studies on Middle Island, which are described in the journal Nature Geoscience, became the key to the puzzle.

From the foregoing, it can be concluded thatIt was the Moon that became the impetus for the birth of life on Earth in the form in which it exists now. True, the Moon influenced only indirectly, only the Sun and cyanobacteria took a direct part in the synthesis of oxygen. But the paradox is that the Sun may in the future deprive the Earth of oxygen, destroying plants and cyanobacteria.