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Evidence of Thermal Metamorphism on the C, G, B, and F Asteroids

1993; American Association for the Advancement of Science; Volume: 261; Issue: 5124 Linguagem: Inglês

10.1126/science.261.5124.1016

1095-9203

T. Hiroi, C. M. Pieters, M. E. Zolensky, M. E. Lipschutz,

Planetary Science and Exploration

Reflectance spectra (0.3 to 2.6 micrometers) of 14 C, G, B, and F asteroids and 21 carbonaceous chondrite powders are compared in detail. Only three thermally metamorphosed CM-Cl chondrites that have a weak ultraviolet absorption are shown to have close counterparts among those asteroids. Reflectance spectra of heated Murchison CM2 chondrite are compared with the average C and G type asteroid spectra. Murchison heated at 600 degrees to 1000 degrees C exhibits a similar weak ultraviolet absorption and provides the best analog for those spectra. Comparison of ultraviolet absorption strengths between 160 C, G, B, and F asteroids and carbonaceous chondrites suggests that surface minerals of most of those asteroids are thermally metamorphosed at temperatures around 600 degrees to 1000 degrees C.