Stardust in Primitive Astromaterials: Insights into the Building Blocks and Early History of the Solar System

• Main Author: Haenecour, Pierre
• Format: Text
• Language: English
• Published: Washington University Open Scholarship 2016
• Subjects: Circumstellar environments; Meteorites; Presolar Grains; Solar System; Stardust; Stars; Astrophysics and Astronomy; Geochemistry; Antarctic; Antarc*
• Online Access: https://openscholarship.wustl.edu/art_sci_etds/748; https://openscholarship.wustl.edu/cgi/viewcontent.cgi?article=1750&context=art_sci_etds

Mixed within the fine-grained material of primitive astromaterials (e.g., meteorites, micrometeorites (MMs) and interplanetary dust particles (IDPs)) are tiny presolar grains, which are remnants of the original material from which the Solar System formed. These presolar grains are (sub-)micrometer-size carbonaceous (e.g., nanodiamonds, SiC, graphites) and oxygen-rich (e.g., oxides, silicates) condensates that formed in circumstellar envelopes or in the ejecta of stellar explosions. The study of presolar grains opened a new field in astronomy, astrophysics and cosmochemistry, allowing the direct in situ study of individual stars and providing ground-truth information on stellar evolution, nucleosynthesis of the elements, and grain condensation in circumstellar envelopes, as well as on the secondary processing of fine-grained material in the solar nebula and on their parent-body asteroids. In this dissertation, I focus on combining the identification and characterization of presolar grains in the most primitive carbonaceous chondrites and fine-grained Antarctic MMs with coordinated in-situ chemical and structural analyses of fine-grained materials in these same samples. In Chapter 1, I introduce the research objectives of the dissertation and provide some basic information on the classification, composition and formation model(s) of unequilibrated extraterrestrial material, in particular primitive meteorites and micrometeorites. I also briefly introduce each of the main types of presolar grains. While each chapter includes a sample and methods section, I also provide here a general description of all the samples and experimental methods used in this dissertation. Chapter 2 provides a detailed review of the isotopic and elemental compositions, mineralogies, and abundances of presolar silicate grains in meteorites, micrometeorites and interplanetary dust particles. In Chapters 3 and 4, I focus on the compositions of the building blocks of our Solar System and their origin(s) in presolar circumstellar environments or ...