{"title":"The Bulk Densities of Small Solar System Bodies as a Probe of Planetesimal Formation","authors":"Misako Tatsuuma, Akimasa Kataoka, Hidekazu Tanaka, Tristan Guillot","doi":"arxiv-2407.21386","DOIUrl":null,"url":null,"abstract":"Constraining the formation processes of small solar system bodies is crucial\nfor gaining insights into planetesimal formation. Their bulk densities,\ndetermined by their compressive strengths, offer valuable information about\ntheir formation history. In this paper, we utilize a formulation of the\ncompressive strength of dust aggregates obtained from dust $N$-body simulations\nto establish the relation between bulk density and diameter. We find that this\nrelation can be effectively approximated by a polytrope with an index of 0.5,\ncoupled with a formulation of the compressive strength of dust aggregates. The\nlowest-density trans-Neptunian objects (TNOs) and main-belt asteroids (MBAs)\nare well reproduced by dust aggregates composed of 0.1-$\\mathrm{\\mu}$m-sized\ngrains. However, most TNOs, MBAs, comets, and near-Earth asteroids (NEAs)\nexhibit higher densities, suggesting the influence of compaction mechanisms\nsuch as collision, dust grain disruption, sintering, or melting, leading to\nfurther growth. We speculate that there are two potential formation paths for\nsmall solar system bodies: one involves the direct coagulation of primordial\ndust grains, resulting in the formation of first-generation planetesimals,\nincluding the lowest-density TNOs, MBAs, and parent bodies of comets and NEAs.\nIn this case, comets and NEAs are fragments or rubble piles of first-generation\nplanetesimals, and objects themselves or rubbles are composed of\n0.1-$\\mathrm{\\mu}$m-sized grains. The other path involves further potential\nfragmentation of first-generation planetesimals into compact dust aggregates\nobserved in protoplanetary disks, resulting in the formation of\nsecond-generation planetesimals composed of compact dust aggregates, which may\ncontribute to explaining another formation process of comets and NEAs.","PeriodicalId":501209,"journal":{"name":"arXiv - PHYS - Earth and Planetary Astrophysics","volume":"28 1","pages":""},"PeriodicalIF":0.0000,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"arXiv - PHYS - Earth and Planetary Astrophysics","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/arxiv-2407.21386","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 0
Abstract
Constraining the formation processes of small solar system bodies is crucial
for gaining insights into planetesimal formation. Their bulk densities,
determined by their compressive strengths, offer valuable information about
their formation history. In this paper, we utilize a formulation of the
compressive strength of dust aggregates obtained from dust $N$-body simulations
to establish the relation between bulk density and diameter. We find that this
relation can be effectively approximated by a polytrope with an index of 0.5,
coupled with a formulation of the compressive strength of dust aggregates. The
lowest-density trans-Neptunian objects (TNOs) and main-belt asteroids (MBAs)
are well reproduced by dust aggregates composed of 0.1-$\mathrm{\mu}$m-sized
grains. However, most TNOs, MBAs, comets, and near-Earth asteroids (NEAs)
exhibit higher densities, suggesting the influence of compaction mechanisms
such as collision, dust grain disruption, sintering, or melting, leading to
further growth. We speculate that there are two potential formation paths for
small solar system bodies: one involves the direct coagulation of primordial
dust grains, resulting in the formation of first-generation planetesimals,
including the lowest-density TNOs, MBAs, and parent bodies of comets and NEAs.
In this case, comets and NEAs are fragments or rubble piles of first-generation
planetesimals, and objects themselves or rubbles are composed of
0.1-$\mathrm{\mu}$m-sized grains. The other path involves further potential
fragmentation of first-generation planetesimals into compact dust aggregates
observed in protoplanetary disks, resulting in the formation of
second-generation planetesimals composed of compact dust aggregates, which may
contribute to explaining another formation process of comets and NEAs.