Micrometeorites and Cosmic Spherules

The East Antarctic ice sheet transports not only meteorite specimens that have fallen onto its surface, but it also contains a mixture of small particles of terrestrial and extraterrestrial origin (Cassidy 1964). The extraterrestrial component of this sediment consists of unmelted micrometeorites (MMs), glassy cosmic spherules, and interplanetary dust particles (IDPs) which include the particles released by comets as they pass through the solar system (Faure and Mensing 2005, 2007). 

Most of the micrometeorites, that fall to the Earth, land in the ocean and are detectable in deep-sea sediment The particles that land on the continents are diluted by terrestrial rock and mineral particles and are subsequently decomposed by chemical wealhering in soils. Fortunately, MMs that fall in Greenland and Antarctica are preserved by being incorporated into the ice sheets from which they are ultimately released when the ice melts or sublimates. Alternatively, the MMs can be recovered by melting the ice in-place and by collecting the sediment that accumulates in the melt cavity. 

The terrestrial component of the dust particles embedded in the ice consists of volcanic ash, finegrained dust derived from soil on the continents, carbon particles released by forest fires, biogenic particles (e.g., the skeletons of diatoms, seeds, and pollen grains), aerosol particles of atmospheric origin, including sea-spray particles that nucleate snow flakes (Section 17.10). In addition, the uppermost layer of snow and fim that was deposited after the start of the Industrial Revolution (i.e., post ad 1850) contains anthropogenic detritus such as flakes of metal, paint, and plastics, fly-ash particles and other combustion products, fibers (composed of wood, cotton, and synthetics), industrial contaminants (e.g., lead), and radioactive nuchdes released by the testing of nuclear weapons and by the operation of nuclear reactors (Faure et al. 1997). 

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See also in sourсe #XX -- [ , , , , ]

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