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Type i cosmic spherules: key to a major, but poorly sampled, asteroid population?
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | Nyquist, L. E. |
| Copyright Year | 1999 |
| Description | 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%/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 compared to ratios in bulk chondrites and chondritic metal. Although the calculated pre-atmospheric Fe/Ni ratio for the spherules is relatively constant at 19 +/- 4 (sigma(sub mean)) 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 or = 3 x 10(exp -4). Thus, Type I spherules do not appear to be ablation products of iron meteorites, in contrast to an earlier suggestion. |
| File Size | 129717 |
| Page Count | 2 |
| File Format | |
| Alternate Webpage(s) | http://archive.org/details/NASA_NTRS_Archive_20000093316 |
| Archival Resource Key | ark:/13960/t4wh7hh8k |
| Language | English |
| Publisher Date | 1999-01-01 |
| Access Restriction | Open |
| Subject Keyword | Astrophysics Distillation Fractionation Populations Iron Meteorites Abundance Iron Discriminators Ocean Bottom Ablation Spherules Asteroids Chromium Chondrites Nickel Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science |
| Content Type | Text |
| Resource Type | Article |
