The air pressure in the exosphere is extremely low due to its high altitude and the distance between the molecules it contains. The exosphere is the Earth's uppermost atmospheric layer, and it is not highly affected by the Earth's gravitational pull.
The exosphere reaches altitudes of 6,200 miles and is connected to outer space. While most molecules in the exosphere are eventually pulled back into the lower layers of the atmosphere by gravity, some particles are released into outer space due to the extremely low gravity and pressure. Molecules in the exosphere typically do not come into contact with each other and move along arcing trajectories before cycling throughout the atmospheric layers.