micrometeorite

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micrometeorite

(mÿ-kroh-mee -tee-ŏ-rÿt) A cosmic dust particle of mass less than about 10–6 gram and diameter less than 0.1 mm. On impact with the Earth's atmosphere the heat absorbed by the particle from atmospheric friction is insufficient to raise it to boiling point. The ratio of heat radiated to heat absorbed is proportional to the inverse of the radius of a particle: those larger than 10–6 gram ablate and form meteors; smaller ones do not. The micrometeorite will be decelerated to a normal free-fall velocity and then drift to the surface of the Earth. On the Moon, however, no deceleration occurs and they impact the surface with the normal geocentric velocity.

micrometeorite

[¦mī·krō′mē·dē·ə‚rīt]
(astronomy)
A very small meteorite or meteoritic particle with a diameter generally less than a millimeter.
References in periodicals archive ?
The micrometeorites were separated by a hand magnet, and the grains obtained from various fractions were subjected to light microscope, XRD, microprobe, and SEM examinations.
This is because the temperature of a comet impact is far higher than that for micrometeorites - providing an environment for 'shock chemistry', in which oxygen tied up in comet ices is liberated to form carbon monoxide.
They examined a large supply of micrometeorites from the same Antarctic ice field as ALH84001.
I'm cautiously excited," said Westphal, who added that the researchers must conduct more tests to ensure that their particles are truly interstellar grains, rather than micrometeorites or even pieces of the spacecraft knocked loose by debris.
Astronomers have suggested three sources of energy that might loosen sodium atoms from the moon's surface and generate the atmosphere: micrometeorites, charged particles of the solar wind, or sunlight.
Even though the moon has no atmosphere, dust can be stirred up from the surface by the impact of micrometeorites.
Several processes may cause Europa's icy surface to deliver small amounts of oxygen to the atmosphere -- among them sublimation (the direct change of a solid to a gas) and impacts from micrometeorites breaking up the surface.
Scientists generally believe that the ions that make up the lunar exosphere are generated at the Moon's surface by interaction with solar photons, plasma in the Earth's magnetosphere, or micrometeorites.
Because the K-T boundary sediments in the Pacific contain vast numbers of these particles, the researchers say the deposit could not have formed from the normally slow buildup of micrometeorites.
There could be microbes living in the ice, but there could also be the dead bodies of microbes that used to live there, and there could be biological molecules that blew in from dust and micrometeorites.
The near-nothingness of aerogels makes them well suited for collecting speeding micrometeorites without shattering the samples, says materials scientist John F.
Several years ago, researchers discovered that this black dust actually contains micrometeorites measuring about one-tenth of a millimeter across.