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7.7: Mesosphere

Difficulty Level: Basic Created by: CK-12
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Next up: A field trip to the mesosophere!

Not so fast. The mesosphere is the least known layer of the atmosphere. The mesosphere lies above the highest altitude an airplane can go. It lies below the lowest altitude a spacecraft can orbit. Maybe that's just as well. 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.

Mesosphere

The mesosphere is the layer above the stratosphere. It rises to about 85 kilometers (53 miles) above the surface. Temperature decreases with altitude in this layer.

Temperature in the Mesosphere

There are very few gas molecules in the mesosphere. This means that there is little matter to absorb the sun’s rays and heat the air. Most of the heat that enters the mesosphere comes from the stratosphere below. That’s why the mesosphere is warmest at the bottom.

Meteors in the Mesosphere

Did you ever see a meteor shower, like the one in Figure below ? Meteors burn as they fall through the mesosphere. The space rocks experience friction with the gas molecules. The friction makes the meteors get very hot. Many meteors burn up completely in the mesosphere.

The Perseid meteor shower with the Milky Way.

Red Sprites and Blue Jets

Red sprites and blue jets are electrical discharges. They are not the same thing as lightning. They more closely resemble the discharges seen in fluorescent tubes. These events occur much higher up in the atmosphere than lightning.

Red sprites occur higher in the atmosphere than blue jets, while both occur higher than lightning.

Polar Mesospheric Clouds

Clouds in the mesosphere are very rare. The ones that exist occur near the poles. The clouds are called polar mesospheric clouds . At the edge of these clouds are noctilucent clouds. They are forming more often now, perhaps as a result of climate change.

Noctilucent clouds are the highest clouds in the atmosphere.

Mesopause

At the top of the mesosphere is the mesopause. Temperatures here are colder than anywhere else in the atmosphere. They are as low as -100° C (-212° F)! Nowhere on Earth’s surface is that cold.

Vocabulary

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

Summary

  • The mesosphere has a very low density of gas molecules.
  • Temperature decreases in the mesosphere with altitude. This is because the heat source is the stratosphere.
  • The mesosphere has red sprites, blue jets, and two types of clouds.
  • The mesosphere is no place for human life!

Practice

Use this resource to answer the questions that follow.

Mesosphere and Thermosphere at http://www.youtube.com/watch?feature=player_embedded&v=mUZ4faPCiDY (1:57)

  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?

Review

  1. How does temperature change with altitude in the mesosphere?
  2. What types of clouds are found in the mesosphere?
  3. How can meteors burn in the mesosphere when the air density is so low?

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Description

Difficulty Level:

Basic

Grades:

6 , 7

Date Created:

Jan 04, 2013

Last Modified:

Jun 16, 2014
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