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Oxygen isotopic evolution of silicate dust in the protosolar disk: 3D Monte Carlo simulation

Presentation #622.03 in the session Protoplanetary Disks - Theory.

Published onApr 03, 2024
Oxygen isotopic evolution of silicate dust in the protosolar disk: 3D Monte Carlo simulation

Oxygen isotope compositions of Solar System materials including the Earth are distinct from that of Sun (McKeegan et al., 2011). This difference has been explained by oxygen isotope exchange between original silicate dust enriched in 16O and water vapor depleted in 16Oinside the snowline (e.g., Yurimoto & Kuramoto, 2004). In order to understand this isotopic exchange reaction in the protosolar disk, we recently discussed the effective reaction temperature of oxygen isotope exchange between water vapor and amorphous silicate dust moving in a steady accretion disk (Ishizaki et al., 2023) using the experimentally determined isotope exchange reaction kinetics (Yamamoto et al., 2018; 2020). We found that the oxygen isotope exchange reaction with water vapor occurs at 650-750 K for amorphous silicate dust with Mg2SiO4 composition (Ishizaki et al., 2023). However, our steady accretion disk model did not discuss the effects of (1) O isotope exchange between amorphous silicate dust and CO gas, which is the reservoir of 16O-rich component, and (2) enhanced abundance of H2O inside the snowline. Both effects should be considered to examine the reaction timescale, the final O isotope composition of dust, and the spatial distribution of reacted dust, i.e., oxygen isotope exchange history of dust in the protosolar disk. In this presentation, we will present the results of our new model of oxygen isotope exchange of amorphous silicate dust in a steady accretion disk, including the exchange reaction kinetics with CO and the change of H2O/CO/dust abundance ratio due to icy pebble accretion.

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