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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]
In atmospheric, earth, and planetary sciences, a scale height, usually denoted by the capital letter H, is a distance (vertical or radial) over which a physical quantity decreases by a factor of e (the base of natural logarithms, approximately 2.718).
Winds at the surface are a few metres per second, reaching 70 m/s or more in the upper troposphere. The stratosphere and mesosphere extend from 65 km to 95 km in height. The thermosphere and exosphere begin at around 95 kilometres, eventually reaching the limit of the atmosphere at about 220 to 250 km.
An atmosphere (from Ancient Greek ἀτμός (atmós) 'vapour, steam' and σφαῖρα (sphaîra) 'sphere') [1] is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low.
The height of the thermopause varies considerably due to changes in solar activity. [16] Because the thermopause lies at the lower boundary of the exosphere, it is also referred to as the exobase. The lower part of the thermosphere, from 80 to 550 kilometres (50 to 342 mi) above Earth's surface, contains the ionosphere.
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.
The moon also has features like a delicate exosphere composed of dust and gas and ice inside permanently shadowed areas that are vulnerable and could be disturbed by continued explorations, the ...
The Ptolemaic system of celestial motion as depicted in the Harmonia Macrocosmica (1661). Science in classical antiquity encompasses inquiries into the workings of the world or universe aimed at both practical goals (e.g., establishing a reliable calendar or determining how to cure a variety of illnesses) as well as more abstract investigations belonging to natural philosophy.