Stratosphere

Stratosphere (pronounced strat-uh-sfeer)

(1) The region of the upper atmosphere extending between the tropopause and mesosphere to about 30 miles (50 kilometers) above the earth, characterized by little vertical change in temperature.

(2) In historic documents, all of the earth's atmosphere lying outside the troposphere (obsolete).

(3) Any great height or degree of anything, as the highest point of a graded scale.

(4) In geology, collectively, those layers of the Earth’s crust which primarily comprise stratified deposits (obsolete).

1908: From the French stratosphère, the construct being strato + sphère (literally "sphere of layers").  It was coined by French meteorologist Léon-Philippe Teisserenc de Bort (1855-1913).  Strato was an inflected form of strātus (a spreading out), the perfect passive participle of sternō (spread) and past participle stem of sternere (to spread out) from the primitive Indo-European root stere- (to spread).  Sphere was from the Middle English spere, from the Old French sphere, from the Medieval Latin sphēra, from the Classical Latin sphaera (ball, globe, celestial sphere), from the Ancient Greek σφαῖρα (sphaîra) (ball, globe) of unknown origin and despite the apparent similarity, not related to the Persian سپهر‎ (sepehr) (sky).  The earlier use of the word, attested in English 1908 and coined in German 1901, was a geological term for part of the Earth's crust and has long been wholly obsolete.  The second major layer of Earth's atmosphere, the stratosphere sits above the troposphere and below the mesosphere.  Itself stratified, the stratosphere’s cooler layers are closest to the Earth’s surface, the higher layers warmed by the absorption of the Sun's ultraviolet radiation in the ozone layer, a reversal of the process in the troposphere where temperature decreases with altitude.  Stratosphere is a noun, and stratospheric & stratospherical are adjectives; the noun plural is stratospheres.

Layers

It was once thought the first living things to enter the stratosphere were some fruit flies, sent there by the US Air Force aboard one of the V-2 rockets seized from the German's wartime missile programme.  Launched in February 1947 from the White Sands Missile Range in New Mexico, the purpose of the flight was to explore the effects of radiation exposure at these then novel high altitudes; the V2 attained a height of 68 miles (109 kilometres) and all fruit flies survived the trip.  It was soon appreciated however that some bacteria or viruses must have been present in or on the V2s launched by the Germans between 1944-1945 and many of these would, at least briefly, have entered the stratosphere but even these appear not to have been the first living (and viruses are in some sense “alive”) things there.

Although the tropopause (the uppermost layer of the troposphere) is thought a barrier to the upward movement of particles, volcanoes are an obvious means by which this could occur although such eruptions are rare.  Bacterial life does however survive in the stratosphere, making it technically, part of the biosphere and, in 2001, dust was collected at a height of 25 miles (41 kilometres) which, upon analysis, was found to contain bacteria of surprisingly large size.  The discovery excited speculation that such large bacterial masses may be incoming to Earth, the suggestion being that (1) the bacteria may have arrived in the stratosphere from space and (2) the possibility that the transfer of bacteria from the Earth to the highly mutagenic stratosphere may have played a role in bacterial evolution.  Among the scientific community, enthusiasm for these theories was restrained.