exosphere

ex·o·sphere  (ks-sfîr)

n.

1. The outermost region of a planet's atmosphere.

2. The outermost layer of the earth's atmosphere, lying above the thermosphere and extending thousands of kilometers into space, from which molecules having sufficient velocity can escape the earth's gravitation.

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exo·spheric (-sfîrk, -sfr-) adj.

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exosphere [ˈɛksəʊˌsfɪə]

n

(Earth Sciences / Physical Geography) the outermost layer of the earth's atmosphere. It extends from about 400 kilometres above the earth's surface

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exosphere  (ks-sfîr)

The outermost region of the Earth's atmosphere, beginning at an altitude of approximately 550 km to 700 km (341 to 434 mi) and merging with the interplanetary medium at around 10,000 km (6,200 mi). The exosphere consists chiefly of ionized hydrogen, which creates the geocorona by reflecting far-ultraviolet light from the Sun. On the remote edges of the exosphere, hydrogen atoms are so sparse that each cubic centimeter might contain only one atom; furthermore, the pressure and gravity are weak enough that atoms in the exosphere can escape entirely and drift into space. Artificial satellites generally orbit in this region. See also mesospherestratospherethermospheretroposphere, See illustration at atmosphere.

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exosphere

the highest portion of the earth’s atmosphere, from which air molecules can escape into space. Cf. ionosphere.

See also: Atmosphere

Thesaurus

Noun

1.

exosphere - the outermost atmospheric layer layer - a relatively thin sheetlike expanse or region lying over or under another atmosphere - the envelope of gases surrounding any celestial body