Table of Contents

The Space Environment and Earth's Atmosphere

What is the purpose of the atmosphere?

The atmosphere protects our planet and is a source of life.

Absorption of harmful radiations

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The atmosphere filters the ultraviolet rays (those rays that are harmful to humans) emitted by the Sun. This phenomenon takes place in the stratosphere.

Greenhouse Effect

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The Earth absorbs other types of short waves from the Sun, which warm the surface of continents and oceans. The direct consequence of this warming is that Earth emits infrared radiation sometimes known as “terrestrial radiation”. This radiation is heat that greenhouse gases in the atmosphere prevent from being scattered into space contributing to the maintainance of a climate favourable to life.

Meteorite Shield

Astronomers believe that the average frequency at which a collision between Earth and a meteorite large enough to have an impact throughout the planet is in the order of once per million years or more. To cause a disaster, a meteorite must be at least one kilometre in diameter. Earth is struck much more often_many times a minute in fact_by smaller aeroliths which, should they reach the ground as is, could nevertheless cause significant damage to animal life and property. Luckily, the atmosphere takes care of them.

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A meteorite usually travels at a speed of 15 km/s. When it breaches the atmosphere at such a velocity, it is subjected to high temperatures (caused by friction) and extreme pressure which, in most cases, cause it to disintegrate. What is left of the meteorite reaches the ground in the form of dust or fragments whose size varies from that of a marble to that of a tennis ball. We can, however, sometimes find larger fragments.

Atmospheric Cycles

The atmosphere also acts as a large conveyor belt throughout the planet playing a key role in providing elements necessary to animal and plant life, such as water, oxygen, carbon and nitrogen.

Let’s look at the water cycle. Water evaporates from the oceans’ surface into the atmosphere where, as clouds, it travels great distances. Above the continents, water suspended in the clouds condenses and falls as precipitation, infiltrating the ground and feeding lakes and streams. The water finally returns to the oceans where the cycle starts over.

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The atmosphere is responsible for constantly distributing the large quantity of carbon dioxide coming from the exhalation of animals, which is transformed into oxygen by the process of photosynthesis. Without this perfectly balanced process, life on Earth would not be possible.

Carbon, absorbed by plants from the air’s carbon dioxide, is transformed into food_the actual plant or its fruit_which enables animals to feed themselves and grow.

Another major source of carbon comes from volcanic activity. This additional quantity of gas is counterbalanced by a phenomenon called “weathering”, by which a chemical reaction occurs between rainwater and rocks to convert carbon dioxide into minerals.

Nitrogen, another key element of life, is part of our protein and DNA composition. There is an abundant amount of nitrogen in the atmosphere (more than 78%), but the form in which it is found in the air is not clean enough for living organisms to use as is. Bacteria found in the ground intervene to capture the nitrogen suspended in the air and convert it into nitrates that can then be drawn by plants on which animals will later feed.

Our atmosphere guarantees a semi-perfect equilibrium that must be maintained between the different elements of these cycles, and which are all essential to life.

Energy Distribution

Globally, earth absorbs solar energy and, in return, diffuses heat toward space. We now know that equatorial regions absorb more heat than they emit and, inversely, the terrestrial radiation of polar regions is greater than the quantity of heat they absorb.

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We can therefore say that equatorial regions have a positive radiation balance, whereas regions closer to the poles have a negative radiation balance. Atmospheric circulation intervenes to re-establish the global balance by transporting the excess energy from the equator to the poles.

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Note that oceans also play a role in transporting energy from warm regions to cold regions through ocean currents such as the Gulf Stream.

Life On Earth

Our planet’s atmosphere protects and stimulates life. Without its qualities that protect us from the elements of space, whether harmful radiation or large aeroliths, life on Earth could not exist.

The atmosphere is almost solely responsible for maintaining the balance of the environment in which we live, which is so favourable to the development of animal and plant life.

The atmospheric cycles and the energy exchange concepts studied reveal the extent to which our atmosphere is precious and the responsibility we have to protect it.