Definitions

1. noun

The outermost layer of a planet’s atmosphere, extending beyond the thermosphere into outer space.

“The exosphere of Earth is where the atmosphere interacts with the solar wind.”

2. noun

The outermost part of the atmosphere of a planet, especially the region where the atmosphere interacts with the interplanetary medium.

“The exosphere of Mars is of great interest to planetary scientists studying its thin atmosphere.”

3. noun

A region of the atmosphere of a planet or moon, outside the homosphere, where the pressure is too low for the atmosphere to exert any appreciable force on objects within it.

“The exosphere of Venus is a critical area of study due to its extreme heat and pressure conditions.”