What is Exosphere?
The '''exosphere''' is a thin, atmosphere-like [[volume]] surrounding a planet or natural satellite. Its molecules are gravitationally bound to that body. The density is so low that the molecules are essentially collisionless.<ref>Steigerwald, William 2015. NASA's LADEE Spacecraft Finds Neon in Lunar Atmosphere. [[NASA]].</ref> In the case of bodies with substantial atmospheres, such as Earth's atmosphere, the exosphere is the uppermost layer, The lightest atmospheric gases such as [[hydrogen]] and [[helium]] exist throughout the exosphere. Heavier ones like [[carbon dioxide]] and atomic [[oxygen]] are near the base. There are two borders to the exosphere; the lower boundary and the upper boundary. The lower boundary is about 500-800 km (300-500 miles) above the surface and is called the exobase. It is also called the [[thermopause]] because it is in between the exosphere and the [[thermosphere]]. The molecules are moving very fast, so the temperature in this zone is thought to be thousands of degrees celsius. == References == {{reflist}} {{sci-stub}} [[Category:Layers of Earth's atmosphere]]