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The exosphere is a thin, atmosphere-like volume surrounding a planet or natural satellite where molecules are gravitationally bound to that body, but where the density is so low that the molecules are essentially collision-less. [1]
The temperature of the thermopause could range from nearly absolute zero to 987.547 °C (1,810 °F). Below this, the atmosphere is defined to be active [clarification needed] on the insolation received, due to the increased presence of heavier gases such as monatomic oxygen. The solar constant is thus expressed at the thermopause.
In the exosphere, beginning at about 600 km (375 mi) above sea level, the atmosphere turns into space, although, by the judging criteria set for the definition of the Kármán line (100 km), most of the thermosphere is part of space. The border between the thermosphere and exosphere is known as the thermopause.
Temperatures drop with increasing altitude to the mesopause that marks the top of this middle layer of the atmosphere. It is the coldest place on Earth and has an average temperature around −85 °C (−120 °F; 190 K). [22] [23]
Average yearly temperature is 22.4 °C, ranging from an average minimum of 12.2 °C to a maximum of 29.9 °C. The average temperature range is 11.4 °C. [6] Variability throughout the year is small (standard deviation of 2.31 °C for the maximum monthly average and 4.11 °C for the minimum). The graph also shows the typical phenomenon of ...
Experts on the United Nations Intergovernmental Panel on Climate Change and at institutions around the world have long warned the long-term global average temperature increase should be kept below ...
The temperature of Mercury's exosphere depends on species as well as geographical location. For exospheric atomic hydrogen, the temperature appears to be about 420 K, a value obtained by both Mariner 10 and MESSENGER. [4] The temperature for sodium is much higher, reaching 750–1,500 K on the equator and 1,500–3,500 K at the poles. [15]
The mesosphere of Venus extends from 65 km to 120 km in height, and the thermosphere begins at approximately 120 km, eventually reaching the upper limit of the atmosphere (exosphere) at about 220 to 350 km. [28] The exosphere begins when the atmosphere becomes so thin that the average number of collisions per air molecule is less than one.