Understanding Earth's Atmosphere Layers

Earth's atmosphere is divided into several layers based on temperature and composition. Moving upwards from the ground, these layers are:

• Troposphere
• Stratosphere
• Mesosphere
• Thermosphere
• Exosphere

Each layer has unique characteristics and plays a vital role in our planet's environment.

The Mesosphere and the Layer Above

The question asks about the layer of very rare air found above the mesosphere. Let's look at the layers in order.

• The troposphere is the lowest layer, where most weather occurs.
• Above the troposphere is the stratosphere, which contains the ozone layer.
• Next is the mesosphere, known for being the coldest layer where meteors burn up upon entering the atmosphere.
• Above the mesosphere is the thermosphere. This layer extends up to about 600-1000 kilometers.
• Finally, the exosphere is the outermost layer, where the atmosphere gradually merges into outer space.

The question specifically asks for the layer directly above the mesosphere that has very rare air. This description fits the thermosphere.

Why Thermosphere is the Correct Answer

The thermosphere is located above the mesosphere and below the exosphere. It is characterized by extremely high temperatures (although the air is so thin that it wouldn't feel hot to us) and, critically for this question, a very low density of air particles. The air is indeed very rare in the thermosphere compared to the layers below it.

Let's examine why the other options are not correct:

• Troposphere: This is the lowest layer, far below the mesosphere.
• Stratosphere: This layer is above the troposphere but below the mesosphere.
• Exosphere: While the exosphere also has very rare air, it is located above the thermosphere, not directly above the mesosphere. The thermosphere is the layer situated between the mesosphere and the exosphere.

Therefore, the layer of very rare air above the mesosphere is the thermosphere.

Revision Table: Summary of Atmospheric Layers

Additional Information about Atmosphere Layers

Understanding the atmosphere layers involves more than just their names and order. Here are some additional points:

• Temperature Trends: Temperature generally decreases with altitude in the troposphere and mesosphere, but increases with altitude in the stratosphere (due to ozone absorption of UV) and thermosphere (due to absorption of high-energy radiation).
• Air Density: The density of air decreases significantly as you move higher through the atmosphere. The troposphere contains about 75% of the atmosphere's mass.
• Phenomena: Specific events happen in different layers. Weather happens in the troposphere. Airplanes typically fly in the lower stratosphere. Meteors burn up in the mesosphere. The aurora borealis and aurora australis occur in the thermosphere. Most satellites orbit in the exosphere.

Knowing the relative positions, characteristics, and phenomena associated with each atmospheric layer is important for understanding Earth's atmosphere.