Earth's atmosphere is made of layers, each with certain characteristics and functions. From weather at ground level to the expanse of space above, the atmosphere is a dynamic and fascinating complex of natural forces.
Layers of the atmosphere are the troposphere, stratosphere, mesosphere, thermosphere, and exosphere. They surround the Earth like gaseous shields.
1. Troposphere: Weather
Closest to the Earth's surface, the troposphere is the layer in which humans live. Extending from ground level to approximately 7-20 km (4-12 mi), it contains most of the atmosphere's mass and almost its water vapor.
The troposphere is about 78% nitrogen and 21% oxygen, with trace amounts of other gases like argon, methane and carbon dioxide. Every day one adult tree releases oxygen equal to breathing needs of two humans.
Temperature decreases with altitude, causing formation of clouds, rain and wind. Mountaintops are colder than valleys. Air pressure is highest at the ground level, decreasing with ascent.
All weather phenomena, like clouds, rain, and storms, occur at this level. Turbulence is caused by significant vertical air movement, mixing and contributing to weather patterns.
The troposphere's thickness varies with latitude. It's thicker at the equator, where heat from the sun causes the air to rise. At the poles it's thinner due to colder temperatures. Thickness can vary up to 20%.
2. Stratosphere: Ozone Layer
Above the troposphere, the stratosphere, reaches up from 7-20 km to 50 km (4-31 mi). This layer is more stable than the troposphere. It contains the ozone layer, which absorbs 97-99% of the Sun's UV radiation.
Temperature increases with altitude. This is due to the absorption of ultraviolet (UV) radiation by the ozone layer. Air pressure continues to decrease with altitude, at a slower rate than in the troposphere.
With less vertical mixing, the stratosphere is fairly stable. Jets often fly in the lower stratosphere, at altitudes of 10-14 km (6-9 mi), to avoid turbulence.
The ozone layer is concentrated in the middle stratosphere. Ozone depletion heightens concerns about increased UV radiation reaching Earth's surface. According to the Word Health Organization, cases of skin cancer are on the rise.
3. Mesosphere: Shield from Space Debris
Extending from 50-85 km (31-53 mi), the mesosphere is the coldest layer of the atmosphere. Air pressure is very low. Temperatures drop 59 -90°C (-130°F).
Meteors and satellites burn up in this layer due to friction with air. Noctilucent Clouds, the highest clouds in the atmosphere, sometimes appear in the mesosphere near the poles in summer.
The mesosphere sits above the stratosphere, extending from about 50 to 85 kilometers (31 to 53 miles) above sea level. In this layer,
One of the mesosphere's defining features is its role in the disintegration of meteoroids. Most meteoroids burn up here to create shooting stars. This phenomenon happen s about 75 km (46 mi) above ground.
Despite its importance, the mesosphere is studied less than other layers due to its altitude and difficulties of exploration. Only a few specialized research missions have successfully gathered information.
4. Thermosphere: Aurora Borealis & Satellites
The thermosphere extends from 85-600 km (53-372 mi). It is characterized by extremely high temperatures up to 2500°C (4500°F), due to the absorption of highly energetic solar radiation. Air pressure is extremely low.
The ionosphere overlaps with the thermosphere and exosphere. This region is ionized by solar radiation, enabling radio communication.
Aurora borealis and australis happen here. Charged particles from the sun collide with atoms and molecules in the thermosphere, creating amazing auroral displays. Many satellites also orbit in the thermosphere.
While the thermosphere is huge it has few air molecules and a very low density. Thus, even at extremely high temperatures, an object wouldn't feel hot in this region.
5. Exosphere: Edge of Space
The outermost layer of the atmosphere, the exosphere, extends from 600 km (372 mi) outwards, eventually fading into the vacuum of space at 10,000 km (6200 mi). In this layer, the atmosphere begins to resemble a vacuum.
Temperature is variable, influenced by solar activity. Air pressure is extremely low and air is very thin. It's made primarily of hydrogen and helium atoms. They can travel hundreds of km without colliding.
The exosphere gradually thins out, with atoms escaping into space. Some satellites and space debris orbit in the exosphere. It has no weather and is inhospitable to known life.
Beyond the Exosphere: Space
Beyond the exosphere is space. It's no longer part of Earth's atmosphere but the realm of interplanetary and interstellar space.
A vacuum, its density of matter is extremely low. It's subject to intense radiation from the sun and other cosmic sources.
Space has no air pressure. Temperature varies from -270°C (-454°F) in the dark to over 120°C (248°F) in sunlight, but can reach absolute zero and is much hotter near stars.
Earth's atmosphere interacts with the interstellar medium, showing past periods of increased interstellar material, including hydrogen and other elements.
These affect the atmosphere and potentially climate. Interstellar media can cause increased hydrogen levels, global noctilucent clouds and a reduction in mesospheric ozone. This can even start ice ages.
Charged particles from the solar wind are found here, and interplanetary magnetic fields extending from the sun. Sound doesn't exist as sound waves can't travel without a medium like air.
High levels of cosmic radiation are a problem for space exploration but also provide valuable data for scientists. The radiation consists of charged particles emitted by the sun.
Electrons, protons, and helium nuclei, they're expelled during solar flares and coronal mass ejections. Solar wind, a stream of charged particles and magnetic fields from the sun, carries radiation through the solar system.
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