Understanding the Composition and Structure of the Atmosphere

Composition of the Atmosphere: The atmosphere is the envelope of the land held around our planet by gravity. It is composed of a set of gases and other gaseous elements in suspension. The atmosphere's presence avoids large oscillations of temperature on the Earth's surface, as solar radiation decreases during the day and prevents excessive heat loss at night. In the absence of the atmosphere, temperatures could reach over 95°C during the day and drop to -180°C overnight. The atmosphere contains the necessary components for organisms to perform their vital processes.

Origin and Balance of the Atmosphere: Gases in the atmosphere originated from the rocks of the Earth approximately 4.6 billion years ago, when the Earth's materials were in a semi-liquid state. This was a result of heat produced by the constant collisions of meteorites. This allowed the gases contained in the rocks to be released, gathering around our planet. This primitive atmosphere could not contain carbon dioxide (5% to 30%) and water vapor, and oxygen was not fully developed. It was less transparent than at present, and some of its gases would be poisonous to current organisms.

The Process of Oxygen Production: Oxygen production began in the oceans for millions of years as a result of the activity of living beings. The first signs of life on Earth emerged from the seabed; single-celled organisms that possessed no nuclei breathed. After about 3.5 billion years, new species began to produce oxygen through photosynthesis. This oxygen gas acted as a poison to ancient organisms. After millions of years, the oceans became saturated with oxygen, allowing living things to transition to terrestrial life. The atmosphere continued to develop, producing more oxygen. The oxygen allows for breathing, enabling the combustion process. Current levels of oxygen are balanced by microorganisms that break down organic material in swamps, a process in which they absorb oxygen and produce methane. The primitive atmosphere saw a decrease in carbon dioxide as marine organisms used this gas for their skeletons.

Structure of the Atmosphere:

• Troposphere: This is the layer closest to the ground, extending from sea level to 11 km in altitude. It contains about 75% of the atmosphere's air, and temperature decreases with height. All climatic phenomena occur in this layer.
• Stratosphere: This layer extends from 11 km to about 80 km in altitude. It contains a narrow layer called the tropopause, which separates it from the troposphere. The stratosphere is where the ozone layer is located.

Ionosphere: The air density is low in this layer, which is characterized by its wealth of ions, which are electrically charged particles. It is in the ionosphere where radio waves relax and return to the Earth.

Exosphere: Starting at about 1,100 km in altitude, in this layer, particles are far apart from one another. These particles can reach temperatures of about 2,500°C during the day and drop to -273°C at night.