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The mesosphere is the third layer of the Earth’s atmosphere, where most meteors burn up. It is the coldest place in the atmosphere, with temperatures dropping as low as -225°F. Noctilucent clouds, which may indicate changes in the Earth’s atmosphere, can be seen in this layer.
Just as the earth’s physical body is made up of many layers, the earth’s atmosphere is also made up of layers. One of them is called the mesosphere. The literal translation is “central sphere,” as it is sandwiched between the major upper and lower layers of the atmosphere. The first layer is the troposphere, the second is the stratosphere, the mesosphere is the third, then above that is the thermosphere and the exosphere. The mesosphere begins about 30 miles (48.2 km) above the surface of the earth and extends about 50 miles (80.4 km).
This layer is where most meteors burn up. Although many believe that streaks of light caused by meteors are shooting stars, they are actually small pieces of rock or metal that strike Earth’s atmosphere at extraordinarily high speeds. The pressure created by this shatters the meteors and causes a transfer of energy from the meteor to the atoms and molecules in the atmosphere. This energy is then released as a “glow” which is mistaken for shooting stars.
The top of the mesosphere is the coldest place in the atmosphere, with temperatures dropping as low as -225°F (about -143°C). Freezing temperatures cause ice to form on rock and metal particles in the atmosphere, which can then form so-called noctilucent clouds. These clouds sit higher than any other cloud in the atmosphere and are only visible when the sun falls below the horizon, and then only near polar latitudes, during the summer months when the mesosphere reaches its coldest temperatures.
Noctilucent clouds have a unique, wave-like appearance and are illuminated in the evening sky by the sun below. They have only been sighted since the late 19th century, but sightings are increasing in frequency and are thought to be increasing in brightness as well. Scientists believe they may indicate changes in the Earth’s atmosphere, primarily a change in climate.
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