The composition of 433 Eros: A mineralogical-chemical synthesis

T. J. McCoy, T. H. Burbine, L. A. McFadden, R. D. Starr, M. J. Gaffey, L. R. Nittler, L. G. Evans, N. Izenberg, P. G. Lucey, J. I. Trombka, J. F. Bell, B. E. Clark, P. E. Clark, S. W. Squyres, C. R. Chapman, W. V. Boynton, J. Veverka

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Abstract

The near-Earth asteroid rendezvous (NEAR) mission carried x-ray/gamma-ray spectrometers and multi-spectral imager/near-infrared spectrometer instrument packages which gave complementary information on the chemistry and mineralogy, respectively, of the target asteroid 433 Eros. Synthesis of these two data sets provides information not available from either alone, including the abundance of non-mafic silicates, metal and sulfide minerals. We have utilized four techniques to synthesize these data sets. Venn diagrams, which examine overlapping features in two data sets, suggest that the best match for 433 Eros is an ordinary chondrite, altered at the surface of the asteroid, or perhaps a primitive achondrite derived from material mineralogically similar to these chondrites. Normalized element distributions preclude FeO-rich pyroxenes and suggest that the x-ray and gamma-ray data can be reconciled with a common silicate mineralogy by inclusion of varying amounts of metal. Normative mineralogy cannot be applied to these data sets owing to uncertainties in oxygen abundance and lack of any constraints on the abundance of sodium. Matrix inversion for simultaneous solution of mineral abundances yields reasonable results for the x-ray-derived bulk composition, but seems to confirm the inconsistency between mineral compositions and orthopyroxene/clinopyroxene ratios. A unique solution does not seem possible in synthesizing these multiple data sets. Future missions including a lander to fully characterize regolith distribution and sample return would resolve the types of problems faced in synthesizing the NEAR data.

Original languageEnglish (US)
Pages (from-to)1661-1672
Number of pages12
JournalMeteoritics and Planetary Science
Volume36
Issue number12
DOIs
StatePublished - 2001

ASJC Scopus subject areas

  • Geophysics
  • Space and Planetary Science

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    McCoy, T. J., Burbine, T. H., McFadden, L. A., Starr, R. D., Gaffey, M. J., Nittler, L. R., Evans, L. G., Izenberg, N., Lucey, P. G., Trombka, J. I., Bell, J. F., Clark, B. E., Clark, P. E., Squyres, S. W., Chapman, C. R., Boynton, W. V., & Veverka, J. (2001). The composition of 433 Eros: A mineralogical-chemical synthesis. Meteoritics and Planetary Science, 36(12), 1661-1672. https://doi.org/10.1111/j.1945-5100.2001.tb01855.x