Actions for High Silicate Crystalline-to-Amorphous Ratios in Comets C

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High Silicate Crystalline-to-Amorphous Ratios in Comets C/2001 Q4 (NEAT) and Hale-Bopp

Author
Harker, D. E.
Published
[2004].
Physical Description
1 electronic document
Additional Creators
Wodward, C. E. and Wooden, D. H.
Online Version

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Summary
Crystalline silicates, by their apparent absence in the ISM, are dust grains that experienced high temperatures in the solar nebula. Mg-rich crystalline silicates formed either by condensation from hot nebular gases (1450 K) or by the annealing of Mg-rich amorphous silicates (approximately 1000 K) in shocks in the 5-10AU region or by radial transport into and out of the hot inner zones, e.g., T(sub d) greater than 1000K at r(sub h) less than 5AU, 10(exp -6) -10(exp -5) solar mass per year, alpha = 10(exp -4) of the early solar nebula. Mg-rich crystalline silicates are found in interplanetary dust particles (IDPs) and produce IR spectral features in many Oort cloud comets. In May 2004, we discovered strong crystalline silicate features in the dynamically new Oort cloud comet C/2001 Q4 (NEAT). Thermal emission modeling of comets Q4 and C/1995 O1 (Hale-Bopp) demonstrate that both these comets have similar, high silicate crystalline-toamorphous ratios of 2.4 and 2.1, respectively, indicating that these icy planetesimals aggregated from similar reservoirs of material or that crystalline silicates were widely distributed within the comet-forming zone. This argues for efficient annealing mechanisms and radial mixing.
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Collection
NASA Technical Reports Server (NTRS) Collection.
Note
Document ID: 20050162288.
Chondrites and the Protoplanetary Disk, Part 4; LPI-Contrib-1218-Pt-4.
Terms of Use and Reproduction
Copyright, Distribution under U.S. Government purpose rights.
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