Diffusion of Oxygen Isotopes in Thermally Evolving Planetesimals and Size Ranges of Presolar Silicate Grains

Abstract

Presolar grains are small particles found in meteorites through their isotopic compositions which are considerably different from those of materials in the Solar System. If some isotopes in presolar grains diffused out beyond their grain sizes when they were embedded in parent bodies of meteorites, their isotopic compositions could be washed out, and hence the grains cannot be identified as presolar grains any more. We explore this possibility for the first time by self-consistently simulating the thermal evolution of planetesimals and the diffusion length of ${}^{18}$O in presolar silicate grains. Our results show that presolar silicate grains smaller than $\sim$ 0.03 $\mu m$ cannot keep their original isotopic compositions even if the host planetesimals experienced maximum temperature as low as 600 ${}^{\circ }$C. Since this temperature corresponds to the one experienced by petrologic type 3 chondrites, the isotopic diffusion can constrain the size of presolar silicate grains discovered in such chondrites to be larger than $\sim$ 0.03 $\mu m$. We also find that the diffusion lengths of ${}^{18}$O reach $\sim$ 0.3-2 $\mu m$ in planetesimals that were heated up to 700-800 ${}^{\circ }$C. This indicates that, if the original size of presolar grains spans a range from $\sim$ 0.001 $\mu m$ to $\sim$ 0.3 $\mu m$ like that in the interstellar medium, the isotopic records of the presolar grains may be almost completely lost in such highly thermalized parent bodies. We propose that isotopic diffusion could be a key process to control the size distribution and abundance of presolar grains in some types of chondrites.

arXiv comment7 pages, 2 figures, accepted for publication in ApJ

References in corpus (9)

• Evolution of Dust in Primordial Supernova Remnants: Can Dust Grains Formed in the Ejecta Survive and be Injected into the Early Interstellar Medium?
• Shattering and coagulation of dust grains in interstellar turbulence
• Coordinated Analyses of Presolar Grains in the Allan Hills 77307 and Queen Elizabeth Range 99177 Meteorites
• Formation of SiC Grains in Pulsation-Enhanced Dust-Driven Wind Around Carbon Rich Asymptotic Giant Branch Stars
• Evolution of the extinction curves in galaxies
• Properties of Dust Grains Probed with Extinction Curves
• Revisiting the lifetime estimate of large presolar grains in the interstellar medium
• Effects of grain shattering by turbulence on extinction curves in starburst galaxies
• Probing the Physical Conditions of Supernova Ejecta with the Measured Sizes of Presolar Al2O3 Grains

Cited by in corpus (2)

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