2018年7月17日
First evidence for silica condensation within the solar protoplanetary disk.
Proceedings of the National Academy of Sciences of the United States of America
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- 巻
- 115
- 号
- 29
- 開始ページ
- 7497
- 終了ページ
- 7502
- 記述言語
- 英語
- 掲載種別
- 研究論文(学術雑誌)
- DOI
- 10.1073/pnas.1722265115
- 出版者・発行元
- NATL ACAD SCIENCES
Calcium-aluminum-rich inclusions (CAIs) and amoeboid olivine aggregates (AOAs), a refractory component of chondritic meteorites, formed in a high-temperature region of the protoplanetary disk characterized by approximately solar chemical and oxygen isotopic (Δ17O ∼ -24‰) compositions, most likely near the protosun. Here we describe a 16O-rich (Δ17O ∼ -22 ± 2‰) AOA from the carbonaceous Renazzo-type (CR) chondrite Yamato-793261 containing both (i) an ultrarefractory CAI and (ii) forsterite, low-Ca pyroxene, and silica, indicating formation by gas-solid reactions over a wide temperature range from ∼1,800 to ∼1,150 K. This AOA provides direct evidence for gas-solid condensation of silica in a CAI/AOA-forming region. In a gas of solar composition, the Mg/Si ratio exceeds 1, and, therefore, silica is not predicted to condense under equilibrium conditions, suggesting that the AOA formed in a parcel of gas with fractionated Mg/Si ratio, most likely due to condensation of forsterite grains. Thermodynamic modeling suggests that silica formed by condensation of nebular gas depleted by ∼10× in H and He that cooled at 50 K/hour at total pressure of 10-4 bar. Condensation of silica from a hot, chemically fractionated gas could explain the origin of silica identified from infrared spectroscopy of remote protostellar disks.
- リンク情報
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- DOI
- https://doi.org/10.1073/pnas.1722265115
- PubMed
- https://www.ncbi.nlm.nih.gov/pubmed/29967181
- PubMed Central
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6055204
- Web of Science
- https://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=JSTA_CEL&SrcApp=J_Gate_JST&DestLinkType=FullRecord&KeyUT=WOS:000438892600049&DestApp=WOS_CPL
- Scopus
- https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85049953239&origin=inward 本文へのリンクあり
- Scopus Citedby
- https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85049953239&origin=inward
- ID情報
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- DOI : 10.1073/pnas.1722265115
- ISSN : 0027-8424
- eISSN : 1091-6490
- ORCIDのPut Code : 47063158
- PubMed ID : 29967181
- PubMed Central 記事ID : PMC6055204
- SCOPUS ID : 85049953239
- Web of Science ID : WOS:000438892600049