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 said language:
-The prefix “exo-”, which means “outside”.
-The noun “sphaira”, which is synonymous with “sphere”.
The exosphere is the outer region of an atmosphere : in the case of the exosphere of planet Earth , it 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 gases disperse until they reach a composition similar to that of outer space.
The exosphere is the layer of the Earth's atmosphere that has the lowest density . It is located above the thermosphere and is in contact with the aforementioned outer space: that is why it is said to be a transit place between the atmosphere and interplanetary space.
Due to the little influence that gravity exerts on the exosphere, some gases found in this layer can escape and go to outer space. These gases, therefore, diffuse into a vacuum .
Another peculiarity of the exosphere is that, due to the small number of particles that it houses due to the low density of the air , heat is not transferred. Temperature is linked to the average speed of the atoms and molecules of a gas: the higher the speed of the particles, the higher the temperature. In the exosphere, particles move very quickly, but this hot temperature is not transferred to the bodies due to the lack of particles. A person feels heat when the particles impact the skin and the transfer of thermal energy occurs, a situation that could not occur in the exosphere.
Other interesting data about the exosphere are the following:
-Its theoretical upper limit is 190,000 kilometers.
-It is considered to have a thickness that reaches 189,000 kilometers.
-In it, temperatures increase during the day and decrease during the night. Likewise, it must be taken into account that temperatures ranging between 0º and 1,700º C can be recorded there.
-From our planet, the part of the exosphere that can be seen is what is called the geocorona.
-Among the main functions it fulfills is the fact that it acts as the first barrier of protection or defense of what is the Earth 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. Because? Because there is very little friction in it.
-Thanks to the exosphere, the thermosphere can slow down its expansion. Otherwise, it must be kept in mind that the atmosphere could not function properly.
It is important to mention, finally, that various artificial satellites orbit in the exosphere. Among them, meteorological satellites .