The exosphere is the outermost layer of Earth's atmosphere. It extends from the top of the thermosphere to the edge of space. The exosphere is composed of extremely low-densitygases, such as hydrogen and helium, as well as some heavier molecules like oxygen and nitrogen. The particles in the exosphere are so far apart from each other that they can travel long distances without colliding with one another.
Boundary with Space: The exosphere gradually transitions into outer space, with no clear boundary. It is the layer where Earth's atmosphere merges with the vacuum of space.