Meteoritics Explained

Meteoritics should not be confused with Meteorology.

Meteoritics is the science that deals with meteors, meteorites, and meteoroids.^{[1] [2]} It is closely connected to cosmochemistry, mineralogy and geochemistry. A specialist who studies meteoritics is known as a meteoriticist.^[3]

Scientific research in meteoritics includes the collection, identification, and classification of meteorites and the analysis of samples taken from them in a laboratory. Typical analyses include investigation of the minerals that make up the meteorite, their relative locations, orientations, and chemical compositions; analysis of isotope ratios; and radiometric dating. These techniques are used to determine the age, formation process, and subsequent history of the material forming the meteorite. This provides information on the history of the Solar System, how it formed and evolved, and the process of planet formation.

History of investigation

Before the documentation of L'Aigle it was generally believed that meteorites were a type of superstition and those who claimed to see them fall from space were lying.

In 1960 John Reynolds discovered that some meteorites have an excess of ¹²⁹Xe, a result of the presence of ¹²⁹I in the solar nebula.^[4]

Methods of investigation

Mineralogy

The presence or absence of certain minerals is indicative of physical and chemical processes. Impacts on the parent body are recorded by impact-breccias and high-pressure mineral phases (e.g. coesite, akimotoite, majorite, ringwoodite, stishovite, wadsleyite).^{[5] [6] [7]} Water bearing minerals, and samples of liquid water (e.g., Zag, Monahans) are an indicator for hydrothermal activity on the parent body (e.g. clay minerals).^[8]

Radiometric dating

Radiometric methods can be used to date different stages of the history of a meteorite. Condensation from the solar nebula is recorded by calcium–aluminium-rich inclusions and chondrules. These can be dated by using radionuclides that were present in the solar nebula (e.g. ²⁶Al/²⁶Mg, ⁵³Mn/⁵³Cr, U/Pb, ¹²⁹I/¹²⁹Xe). After the condensed material accretes to planetesimals of sufficient size melting and differentiation take place. These processes can be dated with the U/Pb, ⁸⁷Rb/⁸⁷Sr,^{[9] 147}Sm/¹⁴³Nd and ¹⁷⁶Lu/¹⁷⁶Hf methods.^[10] Metallic core formation and cooling can be dated by applying the ¹⁸⁷Re/¹⁸⁷Os method to iron meteorites.^{[11] [12]} Large scale impact events or even the destruction of the parent body can be dated using the ³⁹Ar/⁴⁰Ar method and the ²⁴⁴Pu fission track method.^[13] After breakup of the parent body meteoroids are exposed to cosmic radiation. The length of this exposure can be dated using the ³H/³He method, ²²Na/²¹Ne, ⁸¹Kr/⁸³Kr.^{[14] [15]} After impact on earth (or any other planet with sufficient cosmic ray shielding) cosmogenic radionuclides decay and can be used to date the time since the meteorite fell. Methods to date this terrestrial exposure are ³⁶Cl, ¹⁴C, ⁸¹Kr.^[16]

See also

• Glossary of meteoritics
• Meteor
• Meteoroid
• Meteorite

Notes & references

Further reading

• Book: G. J. H. McCall. The history of meteoritics and key meteorite collections : fireballs, falls and finds. 2006. Geological Society. London. 978-1862391949.

Notes and References

1. https://web.archive.org/web/20190720191927/https://www.lexico.com/en/definition/meteoritics meteoritics
2. Encyclopedia: 19 December 2012 . meteoritics, n. . OED Online . .
3. Encyclopedia: 19 December 2012 . meteoriticist, n. . OED Online . Oxford University Press .
4. Reynolds. J.. Isotopic Composition of Primordial Xenon. Physical Review Letters. 31 March 1960. 4. 7. 351–354. 10.1103/PhysRevLett.4.351. 1960PhRvL...4..351R .
5. Coleman. Leslie C.. Ringwoodite and majorite in the Catherwood meteorite. Canadian Mineralogist. 1977. 15. 97–101. 19 December 2012.
6. Ohtani. E.. Ozawa, S. . Miyahara, M. . Ito, Y. . 4 . Mikouchi, T. . Kimura, M. . Arai, T. . Sato, K. . Hiraga, K. . Coesite and stishovite in a shocked lunar meteorite, Asuka-881757, and impact events in lunar surface. Proceedings of the National Academy of Sciences. 27 December 2010. 108. 2. 463–466. 10.1073/pnas.1009338108. 2011PNAS..108..463O . 21187434 . 3021006. free.
7. Ferroir. Tristan. Beck, Pierre . Van de Moortèle, Bertrand . Bohn, Marcel . 4 . Reynard, Bruno . Simionovici, Alexandre . El Goresy, Ahmed . Gillet, Philippe. Akimotoite in the Tenham meteorite: Crystal chemistry and high-pressure transformation mechanisms. Earth and Planetary Science Letters. 1 October 2008. 275. 1–2. 26–31. 10.1016/j.epsl.2008.07.048. 2008E&PSL.275...26F .
8. Hutchison. R.. Alexander, C.M.O. . barber, D.J. . The Semarkona meteorite: First recorded occurrence of smectite in an ordinary chondrite, and its implications. Geochimica et Cosmochimica Acta. 30 June 1987. 51. 7. 1875–1882. 10.1016/0016-7037(87)90178-5. 1987GeCoA..51.1875H .
9. Birck. J.L.. Allègre, C. J.. Chronology and chemical history of the parent body of basaltic achondrites studied by the ⁸⁷Rb-⁸⁷Sr method. Earth and Planetary Science Letters. 28 February 1978. 39. 1. 37–51. 10.1016/0012-821X(78)90139-5. 1978E&PSL..39...37B .
10. Bouvier. Audrey. Vervoort, Jeffrey D. . Patchett, P. Jonathan . The Lu–Hf and Sm–Nd isotopic composition of CHUR: Constraints from unequilibrated chondrites and implications for the bulk composition of terrestrial planets. Earth and Planetary Science Letters. 31 July 2008. 273. 1–2. 48–57. 10.1016/j.epsl.2008.06.010. 2008E&PSL.273...48B .
11. Smoliar. M. I.. Walker, R. J. . Morgan, J. W. . Re-Os Ages of Group IIA, IIIA, IVA, and IVB Iron Meteorites. Science. 23 February 1996. 271. 5252. 1099–1102. 10.1126/science.271.5252.1099. 1996Sci...271.1099S . 96376008.
12. Web site: Re-Os ages of group IIA, IIIA, IVA, and IVB iron from meteorites.. https://web.archive.org/web/20160413133001/https://www.highbeam.com/doc/1G1-18089497.html. dead. 13 April 2016. 19 December 2012.
13. Bogard. D.D. Garrison, D.H . Jordan, auJ.L . Mittlefehldt, D . ³⁹Ar-⁴⁰Ar dating of mesosiderites: Evidence for major parent body disruption < 4 Ga ago. Geochimica et Cosmochimica Acta. 31 August 1990. 54. 9. 2549–2564. 10.1016/0016-7037(90)90241-C. 1990GeCoA..54.2549B .
14. Eugster. O. Cosmic-ray production rates for ³He, ²¹Ne, ³⁸Ar, ⁸³Kr, and ¹²⁶Xe in chondrites based on ⁸¹Kr-Kr exposure ages. Geochimica et Cosmochimica Acta. 31 May 1988. 52. 6. 1649–1662. 10.1016/0016-7037(88)90233-5. 1988GeCoA..52.1649E .
15. Nishiizumi. K.. Regnier, S. . Marti, K. . Cosmic ray exposure ages of chondrites, pre-irradiation and constancy of cosmic ray flux in the past. Earth and Planetary Science Letters. 1 October 1980. 50. 1. 156–170. 10.1016/0012-821X(80)90126-0. 1980E&PSL..50..156N .
16. Nishiizumi. K.. Elmore, D. . Kubik, P. W. . Update on terrestrial ages of Antarctic meteorites. Earth and Planetary Science Letters. 30 June 1989. 93. 3–4. 299–313. 10.1016/0012-821X(89)90029-0. 1989E&PSL..93..299N .