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Can the earth run out of oxygen? Where does oxygen come from on Earth? Key to life on earth

Unlike the hot and cold planets of our solar system, on the planet Earth there are conditions that allow life in a certain form. One of the main conditions is the composition of the atmosphere, which gives all living things the opportunity to breathe freely and protects from the deadly radiation that reigns in space.

What is the atmosphere made of?

The Earth's atmosphere is made up of many gases. Basically which occupies 77%. Gas, without which life on Earth is unthinkable, occupies a much smaller volume, the oxygen content in the air is 21% of the total volume of the atmosphere. The last 2% is a mixture of various gases, including argon, helium, neon, krypton and others.

The Earth's atmosphere rises to a height of 8,000 km. Breathable air exists only in the lower layer of the atmosphere, in the troposphere, which reaches 8 km at the poles, upwards, and 16 km above the equator. As altitude increases, the air becomes thinner and the more oxygen is depleted. To consider what oxygen content in the air is at different heights, we will give an example. At the peak of Everest (altitude 8848 m), the air holds this gas 3 times less than above sea level. Therefore, the conquerors of high mountain peaks - climbers - can climb to its top only in oxygen masks.

Oxygen is the main condition for survival on the planet

At the beginning of the existence of the Earth, the air that surrounded it did not have this gas in its composition. This was quite suitable for the life of the simplest - single-celled molecules that floated in the ocean. They didn't need oxygen. The process began about 2 million years ago, when the first living organisms, as a result of photosynthesis, began to release small doses of this gas obtained as a result of chemical reactions, first into the ocean, then into the atmosphere. Life evolved on the planet and took on a variety of forms, most of which have not survived to our times. Some organisms eventually adapted to life with the new gas.

They learned to use its power safely inside the cell, where it acted as a power plant, in order to extract energy from food. This way of using oxygen is called breathing, and we do it every second. It was breathing that made it possible for the emergence of more complex organisms and people. Over millions of years, the oxygen content in the air has soared to its current level - about 21%. The accumulation of this gas in the atmosphere contributed to the creation of the ozone layer at a height of 8-30 km from the earth's surface. At the same time, the planet received protection from the harmful effects of ultraviolet rays. The further evolution of life forms on water and on land increased rapidly as a result of increased photosynthesis.

anaerobic life

Although some organisms have adapted to the rising levels of the gas being released, many of the simplest life forms that existed on Earth have disappeared. Other organisms survived by hiding from oxygen. Some of them today live in the roots of legumes, using nitrogen from the air to build amino acids for plants. The deadly organism botulism is another "refugee" from oxygen. He quietly survives in vacuum packaging with canned foods.

What oxygen level is optimal for life

Prematurely born babies, whose lungs are not yet fully opened for breathing, fall into special incubators. In them, the oxygen content in the air is higher by volume, and instead of the usual 21%, its level of 30-40% is set here. Toddlers with severe breathing problems are surrounded by air with 100% oxygen levels to prevent damage to the child's brain. Being in such circumstances improves the oxygen regime of tissues that are in a state of hypoxia, and normalizes their vital functions. But its excessive amount in the air is just as dangerous as the lack of it. Too much oxygen in a child's blood can damage the blood vessels in the eyes and cause vision loss. This shows the duality of the properties of the gas. We must breathe it in order to live, but its excess can sometimes become a poison for the body.

Oxidation process

When oxygen combines with hydrogen or carbon, a reaction called oxidation takes place. This process causes the organic molecules that are the basis of life to decay. In the human body, oxidation proceeds as follows. Red blood cells collect oxygen from the lungs and carry it throughout the body. There is a process of destruction of the molecules of the food that we eat. This process releases energy, water and carbon dioxide. The latter is excreted by the blood cells back into the lungs, and we exhale it into the air. A person can suffocate if they are prevented from breathing for more than 5 minutes.

Breath

Consider the oxygen content in the inhaled air that enters the lungs from the outside when inhaled, is called inhaled, and the air that goes out through the respiratory system when exhaled is called exhaled.

It is a mixture of air that filled the alveoli with that which is in the respiratory tract. Chemical composition the air that a healthy person inhales and exhales under natural conditions practically does not change and is expressed in such figures.

Oxygen is the main constituent of air for life. Changes in the amount of this gas in the atmosphere are small. If by the sea the oxygen content in the air contains up to 20.99%, then even in the very polluted air of industrial cities, its level does not fall below 20.5%. These changes show no effect on human body. Physiological disorders appear when the percentage of oxygen in the air drops to 16-17%. At the same time, there is a clear one that leads to a sharp drop in vital activity, and with an oxygen content in the air of 7-8%, a lethal outcome is possible.

Atmosphere in different eras

The composition of the atmosphere has always influenced evolution. At different geological times, due to natural disasters, rises or falls in the level of oxygen were observed, and this entailed a change in the biosystem. Approximately 300 million years ago, its content in the atmosphere rose to 35%, while the planet was inhabited by gigantic insects. The largest extinction of living beings in the history of the Earth happened about 250 million years ago. During it, more than 90% of the inhabitants of the ocean and 75% of the inhabitants of the land died. One version of the mass extinction says that the low oxygen content in the air was to blame. The amount of this gas has dropped to 12% and it is in the lower atmosphere up to a height of 5300 meters. In our era, the oxygen content in atmospheric air reaches 20.9%, which is 0.7% lower than 800 thousand years ago. These figures are confirmed by scientists from Princeton University who examined samples of Greenland and Atlantic ice formed at that time. The frozen water saved the air bubbles, and this fact helps to calculate the level of oxygen in the atmosphere.

What is its level in the air

Active absorption of it from the atmosphere can be caused by the movement of glaciers. As they move away, they reveal vast areas of organic layers that consume oxygen. Another reason may be the cooling of the waters of the oceans: its bacteria absorb oxygen more actively at low temperatures. The researchers argue that the industrial leap and with it the burning of a huge amount of fuel does not have a special impact. The world's oceans have been cooling for 15 million years, and the amount of vital matter in the atmosphere has decreased regardless of human impact. Probably, some natural processes are taking place on Earth, leading to the fact that the consumption of oxygen becomes higher than its production.

Human impact on the composition of the atmosphere

Let's talk about the influence of man on the composition of the air. The level that we have today is ideal for living beings, the oxygen content in the air is 21%. The balance of carbon dioxide and other gases is determined by the life cycle in nature: animals exhale carbon dioxide, plants use it and release oxygen.

But there is no guarantee that this level will always be constant. The amount of carbon dioxide released into the atmosphere is increasing. This is due to the use of fuel by mankind. And it, as you know, was formed from fossils of organic origin and carbon dioxide enters the air. Meanwhile, the largest plants on our planet, trees, are being destroyed at an increasing rate. Kilometers of forest disappear in a minute. This means that part of the oxygen in the air is gradually falling and scientists are already sounding the alarm. The earth's atmosphere is not a limitless pantry and oxygen does not enter it from the outside. It has been developed all the time along with the development of the Earth. It must be constantly remembered that this gas is produced by vegetation in the process of photosynthesis through the consumption of carbon dioxide. And any significant reduction in vegetation in the form of deforestation inevitably reduces the ingress of oxygen into the atmosphere, thereby disturbing its balance.

Only 2.3 billion years ago, the air surrounding the Earth contained no oxygen at all. For the then primitive forms of life, this circumstance was a real gift.

Single-celled bacteria that lived in the primitive ocean did not need oxygen to sustain their life. Then something happened.

How did oxygen appear on Earth?

Scientists believe that as they developed, some bacteria "learned" to extract hydrogen from water. It is known that water is a combination of hydrogen and oxygen, therefore, the by-product of the hydrogen extraction reaction was the formation of oxygen, its release into water, and then into the atmosphere.

Some organisms over time adapted to live in an atmosphere with a new gas. The body has found a way to harness the destructive energy of oxygen and use it for controlled decay. nutrients, during which energy is released, used by the body to maintain its vital functions.

Related materials:

What is the ozone layer and why is its destruction harmful?

This way of applying oxygen is called breathing, which we use daily, and sow the day. Breathing is a way to ward off the oxygen threat: it made possible development on Earth, larger organisms - multicellular, already having a complex structure. After all, it was thanks to the appearance of breath that evolution gave birth to man.

Where did oxygen come from on earth?

Over the millions of years that have passed, the amount of oxygen on earth has increased from 0.2 percent to the current 21 percent of the atmosphere. But bacteria in the oceans are not the only ones to blame for the increase in oxygen in the atmosphere. Scientists believe that colliding continents were another source of oxygen. In their opinion, during the collision, and then during the subsequent divergence of the continents, large amounts of oxygen were released into the atmosphere.

Scientists from China, the US and France have found a new method for tracking the oxygen content in air bubbles contained in polar ice. Thanks to this, they were able to establish that the content of this gas in the Earth's atmosphere over the past 800,000 years has decreased by 0.7 percent. The reason for such an event could be the drop in temperature that has been going on on Earth in the last millions of years. The corresponding one was published in the journal Science.

The researchers decided to find out how the amount of oxygen in the planet's atmosphere has changed over the past 800,000 years by comparing how the ratio of oxygen and nitrogen has changed in ice samples from Greenland and Antarctica. This method was used by scientists for the first time. Unfortunately, for earlier eras, the new method is not applicable, since air bubbles are fixed in glaciers only if the glacier mass is growing. In the past 800,000 years, the glaciers of Greenland and Antarctica as a whole have been growing, and before that, their size was stable or decreasing for many millions of years.

It turned out that over the past 0.8 million years, significant changes have occurred in the oxygen content on Earth. Its concentration decreased by 0.7 percent. Although at first glance this is a small change, in reality it is quite a lot. In order for such a process to take place, oxygen binding should have been more active than its production by plants by about 1.7-2.0 percent. And this is equivalent to billions of tons of gas per year, and what exactly was responsible for its binding remains unclear.

The authors of the work proposed a hypothesis according to which the accelerated binding of oxygen occurred due to the general cooling of the planet's climate in the last few million years. As the researchers note, with a drop in temperature, the amount of oxygen that can dissolve in a unit volume of sea water increases dramatically. At the bottom of the oceans, oxygen is gradually bound by marine sediments containing carbon. In this case, the general cooling of the climate can lead to the binding of significant amounts of oxygen on the seabed. According to calculations, it is long-term and after that the gas lost from the atmosphere does not return there anymore.

If a process of this kind lasted several tens of millions of years, the oxygen content in the air could fall much more significantly, by tens of percent relative to its current level. This corresponds to conditions at altitudes of several kilometers. If this hypothesis is correct, the ongoing global warming has the potential to increase the concentration of oxygen in the air.

At the moment, there is no clear understanding in science of how the concentration of oxygen has changed over the past hundreds of millions of years. It is only known that already 800 million years ago it was enough for the breathing of large animals such as humans, although two times less than today. In the last 500 million years, the climate on the planet was, as a rule, much warmer than today. Therefore, a number of researchers admit that for the main part of this period there was more oxygen in the air than now. In this case, the metabolism of terrestrial animals could be more active than is typical for our time.

Scientists are finding more and more evidence that Mars had conditions for life in the past. British planetary scientists have determined that billions of years ago there was no less oxygen on the Red Planet than on Earth. The Oxford University study was published in the journal Nature.

Scientists find growing evidence that Mars had conditions for life in the past
mars.nasa.gov

Planetologists studied ancient rocks from the Gusev crater on Mars, collected by the Spirit rover. Having determined the proportion of oxides and sulfur in them, they came to the conclusion that their number exceeds that contained in meteorites of the same origin. This surprised the researchers, since meteorites formed much later than the rocks on the Red Planet. If the analyzed minerals were about 3.7 billion years ago, then the meteorites are 180-1400 million years old. This led planetary scientists to the idea that the rocks absorbed oxygen during contact with Mars billions of years ago.

In addition, scientists found that the proportion of oxygen in the Martian rocks was comparable to that contained in the basalts of the young Earth. "Research results indicate that the air shell of Mars was enriched with oxygen 4 billion years ago, long before similar processes occurred on Earth. Such an amount of oxygen appeared on Earth 2.5 billion years ago," scientist Bernard quotes The Daily Mail. Wood. "Oxygen gave this planet a specific color. We tend to think that Mars was a warm and humid planet long before the Earth acquired these properties," Wood said.

NASA has compiled a panorama showing the "Martian bird in flight"

NASA has compiled a panorama showing the "Martian bird in flight"
mars.nasa.gov

Meanwhile, the American space agency NASA has prepared a high-quality panorama with the opportunity to study the rocks of the Red Planet in detail. The panorama, published on the agency's website, was composed of 900 images with a total "mass" of 1.3 billion pixels.

In the photo you can see "shiny objects"
mars.nasa.gov

The images were taken by the Curiosity rover from October 5 to November 16, 2012. The rover was filming with three cameras in the Rocknest area at the bottom of Gale Crater, where it collects dust and rock samples, CBS reports.

Rectangle carved in stone
mars.nasa.gov

When approaching the photo, you can see "shiny objects" as they are signed on the panorama, "a rectangle carved in stone", and even "a Martian bird in flight." "Definitely weird. But it looks like a bird in flight," the caption reads.

The Curiosity rover landed on the surface of Mars on August 6, 2012. On board the spacecraft there are 10 scientific instruments designed for detailed geological and geochemical studies, studying the atmosphere and climate of the planet, searching for water and its traces, organic substances. The instruments are designed to determine whether Mars was once habitable and whether there are places on it suitable for life now.

Only 2.3 billion years ago, the air surrounding the Earth contained no oxygen at all. For the then primitive forms of life, this circumstance was a real gift.

Single-celled bacteria that lived in the primitive ocean did not need oxygen to sustain their life. Then something happened.

How did oxygen appear on Earth?

Some organisms over time adapted to live in an atmosphere with a new gas. The body has found a way to harness the destructive energy of oxygen and use it to control the breakdown of nutrients, which releases energy that the body uses to sustain itself.

Related materials:

Oxygen in the atmosphere

This way of applying oxygen is called breathing, which we use daily, and sow the day. Breathing is a way to ward off the oxygen threat: it made possible the development on Earth of larger organisms - multicellular ones, which already have a complex structure. After all, it was thanks to the appearance of breath that evolution gave birth to man.