An Experimental Investigation of the Planetary Embryo Bow Shock Model as a Chondrule Formation Mechanism

نویسندگان

  • A. M. Perez
  • S. J. Desch
  • D. L. Schrader
  • C. B. Till
چکیده

Introduction: Chondrules are sub-mm to mm-sized igneous inclusions that can comprise up to ~80% of the primitive meteorites called chondrites, and provide us with snapshots of the solar nebula. They are the key to understanding the early history of the Solar System and the formation of terrestrial planets. Chondrules formed in the first few million years (Myr) of the Solar System’s history [e.g., 1], during its protoplanetary disk phase, so understanding the energetic event(s) that melted chondrules is key to using meteoritic data to constrain astrophysical models of the disk. Chondrules display an array of igneous textures that are the result of melting and crystallization. Textures refer to the overall appearance (e.g., size, shape, orientation) of phenocrysts (melt-grown crystals) within a fine grain matrix or mesostasis. The three most common chondrule textures, in the order of their abundance, are (1) porphyritic, (2) radial, and (3) barred [2]. Once these igneous objects were recognized in chondrites, astrophysical models of their melting have been sought, to understand disk conditions and planet formation [3]. Nebular shock models. The community has not settled on any astrophysical model, making it difficult to use the rich and detailed data from chondrules (i.e., petrology, chemical composition, isotopic fractionation, compound chondrule frequency) to constrain conditions and processes in the protoplanetary disk. Nebular shock models are currently the most favored, meeting both the thermal and petrographic constraints to form chondrules. Models include large-scale shocks driven by gravitational instabilities [4,5,6] and bow shocks driven by planetary embryos [7,8]. The bow shock model is highly motivated by the evidence that planet building had already taken place before chondrule formation.

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CHONDRULE FORMATION IN NEBULAR SHOCK WAVES GENERATED BY PLANETESIMALS PASSING THROUGH JOVIAN RESONANCES: RELATIVE IMPORTANCE OF BOW SHOCKS AND IMPACT SHOCKS. L. L. Hood

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تاریخ انتشار 2018