Encyclopedia of Astrobiology

Living Edition
| Editors: Muriel Gargaud, William M. Irvine, Ricardo Amils, Henderson James Cleaves, Daniele Pinti, José Cernicharo Quintanilla, Michel Viso


  • Philippe Claeys
Living reference work entry
DOI: https://doi.org/10.1007/978-3-642-27833-4_808-3


Iridium is a hard, brittle, corrosion-resistant metal with the symbol 77Ir192. It is one of the platinum group elements (PGE – ruthenium, rhodium, palladium, rhenium, osmium, iridium, platinum), which are highly siderophilic and form strong bonds with iron. Most of the terrestrial PGE are concentrated in the core, leaving the mantle and crust highly depleted in Ir (ca. 3 and <0.05 ppb, respectively). In comparison, undifferentiated meteorites are enriched in PGE (ca. 200–500 ppb). Elevated PGE concentrations measured in terrestrial rocks indicate a meteoritic contribution. The detection of the iridium enrichment in the KT boundary clay layer first led to the meteoritic impact hypothesis as a possible cause of the dinosaur extinction. The determination of PGE elemental ratios in impactites can contribute to the identification of the type of impacted meteorite.

See Also


Bioorganic Chemistry Group Element Clay Layer Strong Bond Mass Extinction 
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Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  1. 1.Earth System ScienceVrije Universiteit BrusselBrusselsBelgium