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9.7: Mesosphere

Difficulty Level: At Grade Created by: CK-12
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What can make your blood boil?

Believe it or not, if you were in the mesosphere without a space suit, your blood would boil! This is because the pressure is so low that liquids would boil at normal body temperature.


Above the stratosphere is the mesosphere. Temperatures in the mesosphere decrease with altitude. Because there are few gas molecules in the mesosphere to absorb the Sun’s radiation, the heat source is the stratosphere below. The mesosphere is extremely cold, especially at its top, about -90oC (-130oF).

Air Density

The air in the mesosphere has extremely low density: 99.9% of the mass of the atmosphere is below the mesosphere. As a result, air pressure is very low (Figure below). A person traveling through the mesosphere would experience severe burns from ultraviolet light since the ozone layer, which provides UV protection, is in the stratosphere below. There would be almost no oxygen for breathing. And, of course, your blood would boil at normal body temperature.

Although the mesosphere has extremely low pressure, it occasionally has clouds. The clouds in the photo are mesopheric clouds called noctilucent clouds.


  • The mesosphere has a very low density of gas molecules.
  • Temperature decreases in the mesosphere with altitude because the heat source is the stratosphere.
  • The mesosphere is no place for human life!


Use this resource to answer the questions that follow.


1. Where is the mesophere found?

2. What does it protect us from?

3. What are noctilucent clouds?

4. When can noctilucent clouds be seen?

5. Why can they only be seen at that time?


1. Why would a person get severe burns in the mesosphere?

2. Why would a person's blood boil in the mesosphere?

3. How can meteors burn in the mesosphere when the air density is so low?

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mesosphere Layer between the stratosphere and thermosphere; temperature decreases with altitude.
noctilucent cloud Seen only rarely, these clouds are the highest in the atmosphere.

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Difficulty Level:
At Grade
Date Created:
Feb 24, 2012
Last Modified:
Aug 07, 2016
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