Earth’s atmosphere consists of five layers, each with its own distinct features. The mesosphere is the third layer, located above the stratosphere and below the thermosphere. In this article, we take a closer look at this layer and its defining characteristics.

Although our atmosphere looks like one continuous piece of sky, it is made up of five distinctly different layers: the troposphere, stratosphere, mesosphere, thermosphere, and exosphere. In this article, we focus on the mesosphere, Earth’s third atmospheric layer.

This article not only examines what the mesosphere is but also looks at the characteristics or facts that define it.

Before we look at specific facts about the mesosphere and its defining characteristics, we first need to establish exactly what the mesosphere is:

Mesosphere Definition

The mesosphere is the third of the five layers of the atmosphere, situated above the stratosphere and below the thermosphere. It begins at an altitude of 50 km (30 miles) and extends to 85 km (53 miles). It is Earth’s coldest atmospheric layer and the region where meteoroids and space debris burn up.

“Mesosphere” is derived from the Greek word mesos sphaira, meaning “middle sphere.” It is a very apt description since the mesosphere is situated in the middle of the five layers (with the troposphere and stratosphere below, and thermosphere and exosphere above it.)

Scientists know very little about this layer since it lies at a height above the upper limits of conventional aircraft but below the region where low-orbiting satellites can operate. One of the only ways to study this part of the atmosphere is by using sounding rockets.

(You can learn more about sounding/weather rockets in this article.)

The mesosphere is the layer within which the vast majority of meteorites, space debris, and other objects burn up, providing a relatively small but critical protection to Earth’s surface from smaller meteorite impacts.

As a result of this feature, the mesosphere also contains a fairly high amount of iron and other metallic particles.

The mesosphere contains the same percentages of gases that can be found in the troposphere and stratosphere. The air is at such a low density, though, that the actual amount of gases present in the mesosphere is just a fraction of those found in the troposphere.

Water vapor also continues to diminish as altitude increases. The amount of water vapor present in the mesosphere is so small that it is basically insignificant. 

Ozone is one of the elements that can be found in the mesosphere. Despite the fact that the ozone layer is located in the stratosphere, the mesosphere still contains a measurable amount of ozone.

The mesosphere starts at a height of 50 km (30 miles) just above the stratosphere and reaches as high as 85 km (53 miles) above the surface of the Earth.

Like the troposphere, the temperature in the mesosphere also decreases as the height above the Earth increases. (No temperature inversion takes place, as is the case within the stratosphere.) Near the top of the mesosphere, the temperature can fall to -90° Celsius (-130° Fahrenheit), making it the region with some of the lowest temperatures in the atmosphere.

As weather is, for all intents and purposes, non-existent in the mesosphere, an interesting phenomenon in the form of noctilucent clouds can sometimes be found at altitudes of 80 km (50 miles).

Consisting of ice crystals, they provide a spectacular view from Earth around two hours after sunset. You can find more about this rare phenomenon in this article.

A dynamic feature of the mesosphere is the presence of zonal winds, atmospheric tides, gravity waves, and planetary waves. These waves start in the troposphere and eventually spread into the mesosphere.

In the mesosphere, the waves and tides become unstable and dissipate, creating momentum in the process. It is this momentum that drives global circulation to a great extent.

The mesosphere can be seen as another protective layer of the Earth’s atmosphere. There are two specific “dangers” that it helps to protect us from. Both were already mentioned but needed to be emphasized again.

As I already mentioned, meteorites of various sizes burn up in the mesosphere. It is estimated that a meteorite the size of an automobile enters and is vaporized in the mesosphere every year. (Space rocks smaller than 25 meters (82 feet) are vaporized in this layer before they can reach the Earth’s surface.)

Now imagine the mesosphere did not protect us from meteorites, and we were hit by a meteor shower, with hundreds of rocks 20 meters in size reaching the Earth’s surface at supersonic speeds.

I don’t need to explain what a city like London or New York will look like after being bombarded with meteorites of this size. (We have all seen disaster movies like “Armageddon” that paint a pretty realistic picture of what can actually happen if it weren’t for the mesosphere.)  

The second danger the mesosphere helps protect us from is the Sun’s ultraviolet rays. (No, it is not just the ozone layer in the stratosphere.) A combination of ozone and molecular oxygen in the mesosphere absorbs some solar radiation across different wavelengths.

So, as little as we know about the mesosphere, we know enough to realize that it plays a vital role within the structure of the Earth’s atmosphere.

As is the case with the troposphere and stratosphere, a small boundary separates the mesosphere from the thermosphere. The mesopause forms the border between the two layers.

The relative absence of solar radiation combined with the cooling effect of carbon dioxide in the mesopause makes it the coldest region on Earth, with temperatures falling as low as -100° Celsius (-148° Fahrenheit).

The following list highlights the characteristics and facts of the mesosphere in more detail.

1. 1. The mesosphere is the third layer of the atmosphere (above the troposphere and stratosphere).
   2. It extends from a height of approximately 50 km (30 miles) to 85 km (53 miles) above the Earth’s surface.
   3. It borders the stratosphere below through a thin transitional space called the stratopause.
   4. It borders the thermosphere above through a thin transitional space called the mesopause.
   5. It is characterized by a drop in temperature as altitude increases.
   6. It is the coldest of the five atmospheric layers, with temperatures dropping to -90° Celsius (-130° Fahrenheit) in the mesopause.
   7. Meteoroids and other small space debris burn up in this layer.
   8. A sodium layer 5 kilometers (3.1 miles) thick can be found in the upper regions of the mesosphere.
   9. Electrical discharges, called lightning sprites (also known as red sprites and ELVES), are visual phenomena that occur in the mesosphere.
   10. A rare visual phenomenon called noctilucent clouds occurs at a height of approximately 80 kilometers (50 miles) in the upper mesosphere.
   11. A portion of solar radiation is also absorbed in this layer, although not as effectively as in the stratosphere.
   12. Combined with the stratosphere, it is often referred to as the Middle Atmosphere.
   13. It is the least known of all layers due to its limited accessibility.

This list does not contain all the data available about the mesosphere, but highlights the key facts and characteristics of this layer.

Now that one has a very clear understanding of how many layers are present in our atmosphere, each one with its unique properties, you may never look up at the sky in the same way again.

You will also be able to understand why each layer is so unique and important in its own way. The way weather behaves, the height at which airliners fly, and even where we place our satellites. All should become a lot clearer.

I trust this article helped you to better understand the complex but fascinating structure of layers that make up our atmosphere. I am pretty sure quite a few facts might have caught you off guard, but in a pleasant and intriguing way.

If you are interested in the complete structure and make-up of the atmosphere, this article covers all five atmospheric layers and their relation to each other in more detail.

Until next time, keep your eye on the weather!