Exosphere Facts

Exosphere Facts
The exosphere is one of the five layers of earth's atmosphere. The other layers include the troposphere, stratosphere, mesosphere, and thermosphere. The exosphere is the fifth and outermost layer of the atmosphere, beginning at the upper boundary of the thermosphere and lower exosphere, referred to as exobase, exopause, and the 'critical altitude'. Because the upper boundary of the thermosphere varies from 311 to 621 miles, the beginning point of the exosphere also varies within this distance. The word 'exosphere is derived from the Greek word 'exo' meaning 'outside' or 'external.' Where the exosphere ends space begins.
Interesting Exosphere Facts:
The exosphere begins at a distance of 311 to 621 miles from the earth's surface, and ends at approximately 6200 miles from the earth's surface.
Although the exosphere is the most distance layer of earth's atmosphere it is the layer that is the planet's first line of defense against the sun's rays. It is also the first layer to come into contact and protect the earth from meteors, asteroids, and cosmic rays.
The temperature in the exosphere varies greatly and can range from 0 to over 1700 degrees Celsius. It is colder at night and much hotter during the day.
The air in the exosphere is very thin, and is made up mostly of helium, and hydrogen. Traces of other gases such as atomic oxygen and carbon dioxide can also be found.
The upper level of the exosphere is the farthest point from earth that is still affected by earth's gravity. However this distance would be halfway to the moon, and is only considered to be true in a technical sense. Because of this the true boundary of the exosphere is debatable among scientists.
If the boundary of the exosphere is considered to be where it is still affected by earth's gravity then the exosphere would be the largest part of earth's atmosphere. If the boundary of the exosphere is considered to be approximately 6200 miles from the earth's surface, as many believe, then the thermosphere is the largest portion of the earth's atmosphere.
The geocorona is the name for the exosphere's part that is seen from earth.
The exosphere is perfect for placing satellites as there is very little friction and they are able to orbit fairly easily without being disrupted.
Most of the molecules that exist in the exosphere end up being pulled back into earth's lower atmospheric levels by gravity. Some do make it into outer space however because of the low level of gravity and pressure in the exosphere.
The pressure in the exosphere is created by solar wind storms that compress it.
The exosphere extends into a black/dark blue region beyond the earth, while the mesosphere is dark blue, and closer to the earth are the cloudy areas of the stratosphere and troposphere.
Because the air is so thin in the exosphere the molecules do not collide like they do in lower layers of the atmosphere. Most of the molecules make it back into lower layers of the atmosphere but some zoom out into space instead.

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