Meteoritics

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.{{cite journal|last=Reynolds|first=J.|title=Isotopic Composition of Primordial Xenon|journal=Physical Review Letters|date=31 March 1960|volume=4|issue=7|pages=351–354|doi=10.1103/PhysRevLett.4.351|bibcode = 1960PhRvL...4..351R }}

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).{{cite journal|last=Coleman|first=Leslie C.|title=Ringwoodite and majorite in the Catherwood meteorite|journal=Canadian Mineralogist|date=1977|volume=15|pages=97–101|url=http://canmin.geoscienceworld.org/content/15/1/97.extract|access-date=19 December 2012}}{{cite journal|last=Ohtani|first=E.|author2=Ozawa, S. |author3=Miyahara, M. |author4=Ito, Y. |display-authors=4 |author5=Mikouchi, T. |author6=Kimura, M. |author7=Arai, T. |author8=Sato, K. |author9= Hiraga, K. |title=Coesite and stishovite in a shocked lunar meteorite, Asuka-881757, and impact events in lunar surface|journal=Proceedings of the National Academy of Sciences|date=27 December 2010|volume=108|issue=2|pages=463–466|doi=10.1073/pnas.1009338108|bibcode = 2011PNAS..108..463O |pmid=21187434 |pmc=3021006|doi-access=free}}{{cite journal|last=Ferroir|first=Tristan|author2=Beck, Pierre |author3=Van de Moortèle, Bertrand |author4=Bohn, Marcel |display-authors=4 |author5=Reynard, Bruno |author6=Simionovici, Alexandre |author7=El Goresy, Ahmed |author8=Gillet, Philippe|title=Akimotoite in the Tenham meteorite: Crystal chemistry and high-pressure transformation mechanisms|journal=Earth and Planetary Science Letters|date=1 October 2008|volume=275|issue=1–2|pages=26–31|doi=10.1016/j.epsl.2008.07.048|bibcode = 2008E&PSL.275...26F |url=https://archimer.ifremer.fr/doc/00000/4962/}} 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).{{cite journal|last=Hutchison|first=R.|author2=Alexander, C.M.O. |author3=barber, D.J. |title=The Semarkona meteorite: First recorded occurrence of smectite in an ordinary chondrite, and its implications|journal=Geochimica et Cosmochimica Acta|date=30 June 1987|volume=51|issue=7|pages=1875–1882|doi=10.1016/0016-7037(87)90178-5|bibcode = 1987GeCoA..51.1875H }}

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,{{cite journal|last=Birck|first=J.L.|author2=Allègre, C. J.|title=Chronology and chemical history of the parent body of basaltic achondrites studied by the ⁸⁷Rb-⁸⁷Sr method|journal=Earth and Planetary Science Letters|date=28 February 1978|volume=39|issue=1|pages=37–51|doi=10.1016/0012-821X(78)90139-5|bibcode = 1978E&PSL..39...37B }}

¹⁴⁷Sm/¹⁴³Nd and ¹⁷⁶Lu/¹⁷⁶Hf methods.{{cite journal|last=Bouvier|first=Audrey|author2=Vervoort, Jeffrey D. |author3=Patchett, P. Jonathan |title=The Lu–Hf and Sm–Nd isotopic composition of CHUR: Constraints from unequilibrated chondrites and implications for the bulk composition of terrestrial planets|journal=Earth and Planetary Science Letters|date=31 July 2008|volume=273|issue=1–2|pages=48–57|doi=10.1016/j.epsl.2008.06.010|bibcode = 2008E&PSL.273...48B }} Metallic core formation and cooling can be dated by applying the ¹⁸⁷Re/¹⁸⁷Os method to iron meteorites.{{cite journal|last=Smoliar|first=M. I.|author2=Walker, R. J. |author3=Morgan, J. W. |title=Re-Os Ages of Group IIA, IIIA, IVA, and IVB Iron Meteorites|journal=Science|date=23 February 1996|volume=271|issue=5252|pages=1099–1102|doi=10.1126/science.271.5252.1099|bibcode = 1996Sci...271.1099S |s2cid=96376008}}{{cite web|title=Re-Os ages of group IIA, IIIA, IVA, and IVB iron from meteorites.|url=http://www.highbeam.com/doc/1G1-18089497.html|archive-url=https://web.archive.org/web/20160413133001/https://www.highbeam.com/doc/1G1-18089497.html|url-status=dead|archive-date=13 April 2016|access-date=19 December 2012}} 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.{{cite journal|last=Bogard|first=D.D|author2=Garrison, D.H |author3=Jordan, auJ.L |author4= Mittlefehldt, D |title=³⁹Ar-⁴⁰Ar dating of mesosiderites: Evidence for major parent body disruption < 4 Ga ago|journal=Geochimica et Cosmochimica Acta|date=31 August 1990|volume=54|issue=9|pages=2549–2564|doi=10.1016/0016-7037(90)90241-C|bibcode = 1990GeCoA..54.2549B }} 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.{{cite journal|last=Eugster|first=O|title=Cosmic-ray production rates for ³He, ²¹Ne, ³⁸Ar, ⁸³Kr, and ¹²⁶Xe in chondrites based on ⁸¹Kr-Kr exposure ages|journal=Geochimica et Cosmochimica Acta|date=31 May 1988|volume=52|issue=6|pages=1649–1662|doi=10.1016/0016-7037(88)90233-5|bibcode = 1988GeCoA..52.1649E }}{{cite journal|last=Nishiizumi|first=K.|author2=Regnier, S. |author3=Marti, K. |title=Cosmic ray exposure ages of chondrites, pre-irradiation and constancy of cosmic ray flux in the past|journal=Earth and Planetary Science Letters|date=1 October 1980|volume=50|issue=1|pages=156–170|doi=10.1016/0012-821X(80)90126-0|bibcode = 1980E&PSL..50..156N }} 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.{{cite journal|last=Nishiizumi|first=K.|author2=Elmore, D. |author3=Kubik, P. W. |title=Update on terrestrial ages of Antarctic meteorites|journal=Earth and Planetary Science Letters|date=30 June 1989|volume=93|issue=3–4|pages=299–313|doi=10.1016/0012-821X(89)90029-0|bibcode = 1989E&PSL..93..299N |url=https://digital.library.unt.edu/ark:/67531/metadc703546/}}

• Glossary of meteoritics
• Meteor
• Meteoroid
• Meteorite

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• {{cite book|editor1-last= G. J. H. McCall|title=The history of meteoritics and key meteorite collections : fireballs, falls and finds|date=2006|publisher=Geological Society|location=London|isbn=978-1862391949}}

{{Meteorites}}

Category:Meteoroids

*Meteoritics