Type 1 Cosmic Spherules: Key to a Major, But Poorly Sampled, Asteroid Population?

Details Type 1 Cosmic Spherules: Key to a Major, But Poorly Sampled, Asteroid Population? Type 1 Cosmic Spherules: Key to a Major, But Poorly Sampled, Asteroid Population?

Jan 2000

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000lpico.997...65n&link_type=abstract

Workshop on Extraterrestrial Materials from Cold and Hot Deserts, p. 65

Computer Science

Spherules, Chondrites, Asteroids, Iron Meteorites, Ablation, Isotopes, Discriminators, Abundance

Scientific paper

Herzog et al. have determined Fe, Ni, and Cr abundances in Type I cosmic spherules recovered from the deep sea, and also the isotopic fractionation of these elements during passage of the spherules through the terrestrial atmosphere. Isotopic fractionation for all three elements is typically large, approx.16%(sigma)/amu, corresponding to evaporative mass losses of approx.80-85%, assuming Rayleigh distillation from an open system. The corrected, pre-atmospheric, Cr/Ni and Fe/Ni ratios are shown in Figure 1, where they are compared to these ratios in bulk chondrites and chondritic metal. Although the calculated pre-atmospheric Fe/Ni ratio for the spherules is relatively constant at 19+/-4 (sigmamean, the calculated pre-atmospheric Cr/Ni ratios vary by about two orders of magnitude. The Cr/Ni ratios are thus powerful discriminators for possible modes of origin of the spherules. For example, iron meteorites typically have low Cr contents and low Cr/Ni ratios,:less than or equal to 3 x 10-4. Thus, Type I spherules do not appear to be ablation products of iron meteorites, in contrast to an earlier suggestion.

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