* The exosphere is the outermost layer of Earth's atmosphere. It gradually fades into outer space, with no clear boundary.
* It's extremely thin and diffuse. The particles are so far apart that they rarely collide.
* The exosphere extends thousands of kilometers into space. Some definitions put the outer edge at around 10,000 km, while others go as high as 190,000 km.
Instead of thinking of it as a specific distance, it's more accurate to think of the exosphere as a region where the atmosphere becomes indistinguishable from outer space.
