Exosphere

The exosphere is the outermost layer of Earth's atmosphere, extending from about 500 to 1,000 kilometers (311 to 621 miles) above the Earth's surface to about 10,000 kilometers (6,200 miles) or even up to 190,000 kilometers (118,000 miles) in some definitions[6][15]. The upper boundary of the exosphere is not clearly defined as it gradually merges with outer space[1][3].

The exosphere is composed of extremely low densities of gases, including hydrogen, helium, and traces of other gases like nitrogen, oxygen, and carbon dioxide[2][11]. The atoms and molecules in the exosphere are so far apart that they can travel thousands of kilometers without colliding, and some of these particles can escape into space[11][6].

The temperature in the exosphere can vary greatly, ranging from 0°C to 1700°C, depending on solar activity[4][14]. However, due to the low density of particles, the amount of thermal energy in the exosphere is very low, and it would feel cold to us[12][14].

The exosphere plays a crucial role as the first layer of the Earth's atmosphere to make contact with and shield the Earth from meteors, asteroids, and cosmic rays[2]. Many satellites, including the International Space Station (ISS), orbit within the exosphere[3]. The exosphere is also the region where the Earth's atmosphere interacts with solar wind, and changes in the exosphere can affect atmospheric drag on satellites[2].

Citations:

[1] https://scied.ucar.edu/learning-zone/atmosphere/exosphere

[2] https://www.vedantu.com/geography/exosphere

[3] https://byjus.com/physics/exosphere/

[4] https://www.worldatlas.com/articles/how-cold-is-the-exosphere.html

[5] https://scied.ucar.edu/learning-zone/atmosphere/layers-earths-atmosphere

[6] https://en.wikipedia.org/wiki/Exosphere

[7] https://www.noaa.gov/jetstream/atmosphere/layers-of-atmosphere

[8] https://en.wikipedia.org/wiki/Atmosphere_of_Earth

[9] https://homework.study.com/explanation/what-happens-to-temperature-as-altitude-increases-in-the-exosphere.html

[10] https://spaceplace.nasa.gov/exosphere/en/

[11] https://testbook.com/physics/exosphere

[12] https://www.windows2universe.org/earth/Atmosphere/exosphere_temperature.html

[13] https://www.dictionary.com/browse/exosphere

[14] https://www.ck12.org/flexi/earth-science/thermosphere-and-beyond/what-are-the-temperatures-in-the-exosphere/

[15] https://earthhow.com/exosphere/

[16] https://www.britannica.com/science/exosphere

[17] https://study.com/learn/lesson/exosphere-overview-characteristics.html

[18] https://www.merriam-webster.com/dictionary/exosphere

[19] https://www.sciencedirect.com/topics/earth-and-planetary-sciences/exosphere