In the area above the stratopause, the temperature begins to decrease which identifies the beginning of the mesosphere. The mesosphere extends from about 50 kilometers to about 80 kilometers above the earth’s surface. In the upper mesosphere the temperatures drop to nearly -100 degrees Celsius, making it the coldest part of the atmosphere. The small amount of water vapor present in this layer of the atmosphere form thin clouds made of ice. They are sometimes seen as feathery clouds if struck by the sunlight when the sun is setting.
The mesosphere aids in protecting the earth from being struck by large rocklike materials in space called meteoroids. When meteoroids enter the atmosphere, they burn up in the mesosphere. The burning is caused by the friction between the meteoroid and the atmosphere. When this process occurs it can be seen the sky at night as a streak of light flashing across the sky. It is often referred to as a meteor in the sky. The majority of meteoroids usually burn completely, but sometimes a few pieces actually hit the earth’s surface. These pieces are called meteorites. When artificial satellites fall from orbit, they also burn up when they reach the earth’s atmosphere. However, a few pieces of the United States’ Skylab and Russia’s Cosmos reached the earth’s surface.