Mesosphere
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The mesosphere (from the Greek words mesos = middle and sfaira = ball) is the layer of the Earth's atmosphere that is directly above the stratosphere and directly below the thermosphere. The mesosphere is located about 50-80/85km above Earth's surface. Within this layer, temperature decreases with increasing altitude.
Temperatures in the upper mesosphere fall as low as 200K (about -99°F), varying according to latitude and season. Millions of meteors burn up daily in the mesosphere as a result of collisions with some of the billions of gas particles contained in that layer. The collisions create enough heat to burn the falling objects long before they reach the ground.
The stratosphere and mesosphere are referred to as the middle atmosphere. The mesopause, at an altitude of about 80 km, separates the mesosphere from the thermosphere—the 2nd outermost layer of the Earth's atmosphere.
Noctilucent clouds are located in the mesosphere.