Antarctic micrometeorites

Esser and Turekian (1988) estimated an accretion rate of extraterrestrial particles in ocean bottom and in varved glacial lake deposit on the basis of osmium isotope systematics and concluded a maximum accretion rate of between 4.9 x 104 and 5.6 x 104 tons/a. The discrepancy between this estimate and those derived from helium can easily be attributed to the difference in the size of the cosmic dust particles under consideration. Cosmic dusts of greater than a few ten micrometers may not be important in the helium inventory of sediments because the larger grains are likely to lose helium due to atmospheric impact heating (e.g., Brownlee, 1985). Stuart et al. (1999) concluded from studies on Antarctic micrometeorites that 50- to 1 OO-qm micrometeorites may contribute about 5% of the total flux of extraterrestrial 3He to terrestrial sediments. Therefore, the helium-based estimate deals only with these smaller particles. 

Stuart, F. M., Harrop, P. J., Knott, S., Turner, G. (1999) Laser extraction of helium isotopes from Antarctic micrometeorites Source of He and implications for the flux of extraterrestrial 3He to earth. Geochim. Cosmochim. Acta, 63, 2653-65. 

Presolar grains are found in small quantities (with concentrations of ppb to several 100 ppm, see Table 2.1) in all types of primitive Solar System materials (Lodders Amari 2005 Zinner 2007). This includes primitive meteorites (the chondrites), IDPs, some of which might originate from comets, Antarctic micrometeorites (AMMs), and samples from comet Wild 2 collected by NASA s Stardust mission. Presolar grains are nanometer to micrometer in size. The isotopic compositions, chemistry, and mineralogy of individual grains with sizes >100 nm can be studied in the laboratory. Important analysis techniques are secondary ion mass spectrometry (SIMS) and resonance ionization mass spectrometry (RIMS)... 

Engrand C., McKeegan K. D., and Leshin L. A. (1999) Oxygen isotopic compositions of individual minerals in Antarctic micrometeorites further links to carbonaceous chondrites. Geochim. Cosmochim. Acta 63, 2623-2636. 

Clemett S. J., Chillier X. D. E., Gillette S., Zare R. N., Maurette M., Engrand C., and Kurat G. (1998) Observation of indigenous polycyclic aromatic hydrocarbons in giant carbonaceous Antarctic micrometeorites. Origins Life Evol. Biosphere 28, 425-448. 

Fig. 4. Isotopic variations of hydrogen in the Solar System (adapted from Robert et al. 2000). The deuterium/ hydrogen ratio of different components is normalized to the D/H ratio of the Sun (as it was before deuterium burning), which is thought to represent H2 in the protosolar nebula. Numbers along the y-axis represent the numbers of cases. Terrestrial hydrogen is enriched in deuterium by a factor of about six relative to solar. Among Solar System objects analysed so far, carbonaceous chondrites, Antarctic micrometeorites (Engrand Maurette 1998) and chondruies from LL3 chondrites present a distribution of D/H values that centre around the terrestrial D/H ratio. Notably, comets analysed so far (Halley, Hale Bopp and Hyakutake, references given by Dauphas et al. (2000)) present D/H values about two times higher than the terrestrial value.

Kurat, G., Koeberl, C., Presper, T., Brandstat-TER, F. Maurette, M. 1994. Petrology and geochemistry of Antarctic micrometeorites. Geochimica et Cosmochimica Acta, 58, 3879-3904. 

Genge MJ, Gileski A, Grady MM (2005) Chondrules in Antarctic micrometeorites. Meteorit Planet Sci 40(2) 225-238 Gilmour JD, Whitby JA, Turner G (1998) Xenon isotopes in irradiated ALH 84001 Evidence for shock-induced trapping of ancient martian atmosphere. Geochim Cosmochim Acta 62 2555-2571... 

Terada K, Yada T, Kojima H, and 21 additional persons (2001) General characterization of Antarctic micrometeorites collected by the 39th Japanese Antarctic Research Expedition Consortium studies JARE AMMs (II). Antarctic Meteorite Res 14 89-107, Tokyo, Japan Terada K, Monde T, Sano Y (2003) Ion microprobe U-Th-Pb dating of phosphates in martian meteorite ALH 84001. Meteorit Planet Sd 28(11) 1697-1703 Thiel E, Schmidt RA (1961) Spherules from the Antarctic ice cap. J Geophys Res 66 307-310 Thomas-Keprta KL, McKay DS, Wentworth SJ, Stevens TO, Taunton AE, Allen CC, Coleman A, Gibson EK Jr, Romanek... 

Brinton, K.L.E, Engrand, C, Glavin, D.R, Bada, J.L., Maurette, M. (1998) A search for extraterrestrial amino acids in carbonaceous Antarctic micrometeorites. Origins of Life and Evolution of the Biosphere, 28(4-6), 413-424. 

The number of scientific articles published on meteorites has increased dramatically in the last few years few of these, however, concern themselves with small meteorites, the size of which lies between that of the normal meteorites (from centimetres to metres in size) and that of interplanetary dust particles. In the course of an Antarctic expedition, scientists (mainly from French institutions) collected micrometeorites from 100 tons of Antarctic blue ice (Maurette et al 1991). These micrometeorites were only 100 400 pm in size five samples, each consisting of 30-35 particles, were studied to determine the amount of the extraterrestrial amino acids a-aminoisobutyric acid (AIBS) and isovaline—both of which are extremely rare on Earth—which they contained. The analysis was carried out using a well-tested and extremely sensitive HPLC system at the Scripps Institute, La Jolla. Although the micrometeorites came from an extremely clean environment, the samples must have been contaminated, as they all showed traces of L-amino acids. Only one sample showed a significantly higher concentration of AIBS (about 280 ppm). The AIBS/isovaline ratio in the samples also lay considerably above that previously found in CM-chondrites. 

Maurette, M., Olinger, C., Christophe Michel-Levy, M. C., Kurat, G., Pourchet, M., Brandstatter, F., Bourot-Denise, M. (1991) A collection of diverse micrometeorites recovered from 100 tons of Antarctic blue ice. Nature, 351, 44-7. 

From a large collection of micrometeorites extracted from Antarctic old blue ice in the size range of 50 to 100 m (of which carbonaceous micrometeorites represent 80% of the samples and contain 2% carbon), Barbier et al. (1998) concluded that they might have brought more carbon to the surface of the primitive earth than that involved in the present surficial biomass. One assumes that the original carbon... 

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). 

Harvey RP (2003) The origin and significance of Antarctic meteorites. Chemie der Erde 63 93-147 Harvey RP, Maurette M (1990) The best cosmic dust source in the world The origin and significance of the Walcott Neve, Antarctica, micrometeorites. Lunar and Planetary Science Conference, vol. 21—. LPI, Houston, TX, pp 569-578 Harvey RP, McSween HY Jr (1996) A possible high-tempera-ture origin for the carbonates in the martian meteorite ALH 84001. Nature 382 49-51... 

Kiefer WS (2003) Melting in the martian mantle Shergottite formation and implications for present-day mantle convection on Mars. Meteorit Planet Sci 39(12) 1815-1832 King EA, Wagstaff J (1981) Micrometeorites from Antarctic ice cores. Ant J US 16(5) 92-93... 

Wadhwa M, Lugmair GW (1996) The formation age of carbonates in ALH 84001. Abstract Meteorit Planet Sci 3LA145 Wagstaff J, King EA (1981) Micrometeorites and possible cometary dust from Antarctic ice cores. Lunar Planetary Science Conference, vol. 13(3). LPI, Houston, Texas, pp 1124-1126... 

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