1. the outermost layer of Earth’s atmosphere, extending from about 500 kilometers above the surface into space
Usage: atmospheric science

Examples

• The exosphere is where satellites orbit Earth.
• In the exosphere, gas molecules are so sparse they rarely collide.
• The International Space Station orbits within the exosphere.
• Scientists study the exosphere to understand atmospheric escape.
• The exosphere gradually merges with outer space.
• Hydrogen and helium are the main gases found in the exosphere.