What is the importance of the exosphere layer?

I don't have a textbook for my class, so I'm using my brothers old textbook from when he was in school, and its not even listed in there. I can't find much about the exosphere online either, so if anybody knows anything can you help me please?

I need to know the importance of the exosphere and the chemical composition in the exosphere.

All help is appreciated. Thank you!


The outermost layer of Earth's atmosphere extends from the exobase upward. Here the particles are so far apart that they can travel hundreds of km without colliding with one another. Since the particles rarely collide, the atmosphere no longer behaves like a fluid. These free-moving particles follow ballistic trajectories and may migrate into and out of the magnetosphere or the solar wind. The exosphere is mainly composed of hydrogen and helium.