Atmospheric iridium at the South Pole as a measure of the meteoritic component

The measurement of iridium (Ir) in atmospheric samples is important because it gives information on the short-term flux of extraterrestrial material without interference from fragmentation products from large bodies. Such information cannot be obtained from sediment samples, because sediment samples integrate over millions of years and include contributions of large bodies impacted in that time period. In addition to flux information, through the analysis of Ir in atmospheric samples we can also evaluate a possible contribution of extraterrestrial material to the unusual enrichment of chalcophilic elements in a remote atmosphere. We present here a determination of average particle-borne Ir concentration in the South Pole atmosphere. The average values of (7.3±3.1)×l0–17g m–3 suggests that the concentration of extraterrestrial material in the South Pole atmosphere is not large enough to explain the enrichments of anomalously enriched elements; however, meteoritic material contributes significantly to the observed concentrations of Co, Fe and Mn. We estimate an accretion rate for background extraterrestrial material of 11,000 tons annually.


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Citation Formats
S. G. Tuncel, “Atmospheric iridium at the South Pole as a measure of the meteoritic component,” Nature, pp. 703–705, 1987, Accessed: 00, 2020. [Online]. Available: