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Isotopic compositions of cometary matter returned by Stardust
Kevin D McKeegan1, Jerome Aléon, John Bradley
1Department of Earth and Space Sciences, University of California Los Angeles, Los Angeles, CA 90095-1567, USA. mckeegan@ess.ucla.edu
Science (New York, N.Y.)
|December 16, 2006
Summary
Comet 81P/Wild 2 contains materials from both the inner and outer solar system, not just pristine presolar matter. Isotopic analysis reveals a mix of origins, challenging the idea of a purely primordial comet.
Area of Science:
- Cosmic Dust Analysis
- Cometary Science
- Isotope Geochemistry
Background:
- Comets are remnants from the early solar system, offering clues to its formation.
- Comet 81P/Wild 2 has been studied for its unique composition, potentially preserving primordial materials.
Purpose of the Study:
- To investigate the isotopic composition of comet 81P/Wild 2 particle fragments.
- To determine the origin of materials within the comet and assess its pristine nature.
Main Methods:
- Analysis of hydrogen, carbon, nitrogen, and oxygen isotopic compositions in comet fragments.
- Examination of mineralogical and isotopic signatures of individual grains.
Main Results:
- Isotopic heterogeneity was observed, but extreme anomalies were rare, suggesting limited presolar material.
- Nonterrestrial nitrogen and neon isotopes indicate the presence of indigenous organic and volatile matter.
- Most silicates and oxides showed solar system isotopic origins, with one refractory grain exhibiting (16)O enrichment, indicative of inner solar system formation.
Conclusions:
- Comet 81P/Wild 2 is not a pristine aggregate of presolar materials.
- The comet contains a mixture of materials from both the inner and outer solar system.
- Evidence suggests high-temperature inner solar system material was transported to the Kuiper Belt before comet accretion.
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