First evidence for silica condensation within the solar protoplanetary disk

Mutsumi Komatsu*, Timothy J. Fagan, Alexander N. Krot, Kazuhide Nagashima, Michail I. Petaev, Makoto Kimura, Akira Yamaguchi


研究成果: Article査読

28 被引用数 (Scopus)


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 a16O-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.

ジャーナルProceedings of the National Academy of Sciences of the United States of America
出版ステータスPublished - 2018 7月 17

ASJC Scopus subject areas

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