noun
- the outermost layers of a planet’s atmosphere where atmospheric particles can escape to space
Usage: astronomy; atmospheric science
Examples
- The exospheres of gas giant planets extend far beyond their visible surfaces.
- Scientists study the exospheres of Mars and Venus to understand atmospheric escape.
- Earth’s exosphere begins at about 500 kilometers above the surface.
- The exospheres of the outer planets contain mostly hydrogen and helium.
- Spacecraft must pass through planetary exospheres when approaching other worlds.
- Temperature variations in exospheres can affect satellite orbits.