The first thing to do to know the meaning of the term exosphere is to discover its etymological origin. In this case, we can state that it is a word that derives from Greek, since it is the result of the sum of several components of that language:
-The prefix “exo-”, which means “out”.
-The noun “sphaira”, which is synonymous with “sphere”.
The exosphere is the outer region of a atmosphere: in the case of exosphere of planet Earth, begins at a distance of between 300 and 1,000 kilometers from the surface and extends up to 10,000.
The concept, which can also be pronounced with an accent on the third syllable (exosphere), refers to the atmospheric layer in which the gases they are dispersing until they reach a composition similar to that of outer space.
The exosphere is the layer of the Earth’s atmosphere that has lower density. It is located on the thermosphere and it is in contact with the aforementioned outer space: that is why it is said to be a place of transit between the atmosphere and interplanetary space.
Due to the little influence exerted by the force of gravity In the exosphere, some gases found in this layer can escape and go into outer space. Said gases, therefore, get to diffuse in the empty.
Another peculiarity of the exosphere is that, due to the small amount of particles that it shelters by the low density of the air, the heat is not transferred. Temperature is linked to the average speed of the atoms and molecules in a gas: the higher the speed of the particles, the higher the temperature. In the exosphere, the particles move very quickly, but this hot temperature is not transferred to the bodies because of the shortage of particles. A person feels the heat when the particles impact against the skin and the transfer of thermal energy takes place, a situation that could not occur in the exosphere.
Other data of interest about the exosphere are the following:
-Its theoretical upper limit is 190,000 kilometers.
-It is considered that it has a thickness that reaches 189,000 kilometers.
-In it the temperatures increase during the day and decrease at night. Likewise, it must be taken into account that temperatures ranging between 0º and 1,700º C can be registered in it.
-From our planet, the part of the exosphere that can be seen is the one that receives the name of geocorona.
-Among the main functions that it fulfills is the fact that it comes to act as the first barrier of protection or defense of what the Earth is against the rays of the sun. In the same way it acts as such against asteroids, meteors and even cosmic rays.
-In it the satellites have the peculiarity that they can orbit with remarkable ease. Why? Because there is very little friction in it.
-Thanks to the exosphere, the thermosphere can slow down its expansion. Otherwise, it must be borne in mind that the atmosphere could not function properly.
Finally, it is important to mention that the exosphere is orbited by various satellites artificial. Among them, meteorological satellites.