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The mesosphere is one of the layers of the Earth’s atmosphere. It lies between the thermosphere and the stratosphere. This region of the atmosphere starts at 50 km above the Earth’s surface and its upper boundary rangers anywhere from 85 km to 100 depending on where the portions of the mesosphere are located. The mesosphere along with the thermosphere and the stratosphere is called the middle atmosphere. Its boundary is defined by two layers. The first is the boundary between the stratosphere and the mesosphere is called the stratopause and the other that lies between the mesosphere and the thermosphere is that layer that lies between the mesopause and the thermosphere. The mesopause is that area of the atmosphere that is last one that is uniform in composition before reaching the outermost layers.
The temperature of the atmosphere starts getting colder once you reach the mesosphere. The mesosphere can get as cold as -100 degrees Celsius. This is because of decreased solar heating and Carbon Dioxide radiative emission. This portion of the atmosphere has a lot of tidal turbulence to zonal winds, gravity waves, and planetary waves.
The mesosphere is known for many different functions and limits for aerospace. The first is that is the main line of defense for meteors that enter the Earths’ atmosphere. Thanks to the composition of the air in this region meteors encounter air particles often enough to heat up and vaporize. This helps spare the Earth’s surface from the many meteors and meteorites that enter the Earth’s atmosphere. The mesosphere is also the region where the height allowed for aircraft is. Any higher and planes and other air cannot fly since the air is too thin to use for suitable thrust. The boundary for conventional space flight also begins here. The line is arbitrarily designated as the beginning of space even though that is much higher and less distinct.
The mesosphere demonstrates how different the atmosphere is in composition showing the transition from uniform composition to the more stratified and separated elements found in the higher levels of the Earth’s atmosphere. At the same time there is much that is still not known about the mesosphere. Its unique height makes it difficult to send aircraft or space craft to gather data.
We have written many articles about the mesosphere for Universe Today. Here’s an article about the Earth’s atmosphere, and here’s an article about the layers of the atmosphere.
We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.