Fine-Gained CAIs in Comet Samples: Moderate Refractory Character and Comparison to Small Refractory Inclusions in Chondrites

[摘要] Examination of >200 comet Wild 2 particles collected by the Stardust (SD) mission shows that the CAI abundance of comet Wild 2's rocky material is near 1% and that nearly 50% of all bulbous tracks will contain at least one recognizable CAI fragment. A similar abundance to Wild 2 is found in a giant cluster IDP thought to be of cometary origin. The properties of these CAIs and their comparison with meteoritic CAIs provide important clues on the role of CAIs in the early Solar System (SS) and how they were transported to the edge of the solar nebula where Kuiper Belt comets formed. Previously, only two CAIs in comet Wild 2 had been identified and studied in detail. Here we present 2 new Wild 2 CAIs and 2 from a giant cluster cometary IDP, describe their mineralogical characteristics and show that they are most analogous to nodules in spinel-rich, fine-grained inclusions (FGIs) observed in CV3 and other chondrites. Additionally, we present new O isotope measurements from one CAI from comet Wild 2 and show that its oxygen isotopic composition is similar to some FGIs. This is only the second CAI from Wild 2 in which O isotopes have been measured.

[发布日期] 2017-03-20

[学科分类] 空间科学