小行星诞生时更大：气体辅助植入小行星带期间表面质量烧蚀的启示
Asteroids were born bigger: An implication of surface mass ablation during gas-assisted implantation into the asteroid belt
AI总结：
本研究模拟木星、土星迁移与气体盘表面烧蚀对植入小行星带星子的影响，表明多数成分星子会缩小并使SFD变陡，暗示最大C型小行星诞生时更大。
摘要：
小行星带中碳质小行星的起源尚未被完全理解。主流假说认为，它们并非诞生于当前位置，而是在太阳系历史早期被植入小行星带。我们研究了木星和土星在其诞生盘中的迁移与生长如何影响附近的星子，以及随后星子向小行星带的植入。我们考虑了当星子穿过气体盘时，由气体盘介质与星子表面之间的热加热和摩擦加热所导致的星子表面烧蚀效应。我们开展了模拟，考虑了不同成分的星子，包括富水冰星子、贫水冰星子、富有机物星子和富铁橄榄石星子。我们的发现表明，无论巨行星的迁移历史如何，被植入小行星带的富水冰、富有机物和富铁橄榄石星子通常在植入小行星带期间经历表面烧蚀，从而尺寸缩小。具有类似顽火辉石成分的星子对表面烧蚀不敏感，保留了其原始尺寸。通过假设初始星子尺寸-频率分布，我们的结果表明，在表面烧蚀作用下，被植入小行星带的星子群体呈现出比初始SFD斜率略陡的SFD斜率。这对本研究中考虑的所有巨行星迁移历史都成立，但Grand-Tack模型除外，在该模型中SFD斜率基本保持不变。总之，我们的结果表明，小行星带中最大的C型小行星可能在诞生时更大。植入小行星带期间的高强度表面烧蚀甚至可能使早期分异的C型星子的核暴露出来。
英文摘要：
The origins of carbonaceous asteroids in the asteroid belt is not fully understood. The leading hypothesis is that they were not born at their current location but instead implanted into the asteroid belt early in the Solar System history. We investigate how the migration and growth of Jupiter and Saturn in their natal disk impact nearby planetesimals and subsequent planetesimal implantation into the asteroid belt. We account for the effects of surface ablation of planetesimals caused by thermal and frictional heating between the gas-disk medium and planetesimal surface, when planetesimals travel through the gas disk. We have performed simulations considering planetesimals of different compositions as water-ice rich planetesimals, water-ice poor planetesimals, organic-rich planetesimals, and fayalite-rich planetesimals. Our findings indicate that, regardless of the migration history of the giant planets, water-ice rich, organic-rich, and fayalite-rich planetesimals implanted into the asteroid belt generally experience surface ablation during implantation in the asteroid belt, shrinking in size. Planetesimals with enstatite-like compositions were inconsequential to surface ablation, preserving their original sizes. By assuming an initial planetesimal size-frequency distribution, our results show that -- under the effects of surface ablation -- the planetesimal population implanted into the asteroid belt shows a SFD slope slightly steeper than that of the initial one. This holds true for all migration histories of the giant planets considered in this work, but for the Grand-Tack model where the SFD slope remains broadly unchanged. Altogether, our results suggest that the largest C-type asteroids in the asteroid belt may have been born bigger. High-degree surface ablation during implantation into the asteroid belt may have even exposed the cores of early differentiated C-type planetesimals.
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