Distinct origins for CM and CI-like bodies: Saturn formation region versus trans-Neptunian disk
Authors: Anderson Sarah , Vernazza Pierre , Brož Miroslav 
Published: July 2024

AbstractTo date, the vast majority of meteorites (&#8805;99%) originate from asteroids in orbits between Mars and Jupiter, yet reaching a consensus on how their diverse chemical, compositional, and isotopic characteristics align with an in-situ formation model within the asteroid belt remains elusive. Recent dynamical models, leveraging measurements from carbonaceous chondrites (CCs), suggest that meteorites may originate from varied heliocentric distances, spanning from the terrestrial planet formation zone to the Kuiper Belt [1, 2, 3]. This broad range is evident in the distribution dichotomies among CCs, especially between CM chondrites (Ch, Cgh-types) and CI chondrites (B, C, Cb, and Cg-types), which collectively account for over 50% of the asteroid belt's mass, excluding Ceres&#160; [4, 5, 6]. These groups show distinctly different spatial distributions (Fig. 1): CM-like bodies display a Gaussian profile, whereas CI-like bodies show an asymmetric distribution, similar to comet-like P-type asteroids [7]. Our study aims to explore the formation and migration history of these asteroid types within the context of giant planet evolution and solar system dynamics to determine whether CM and CI chondrites originated from different locations or at different times.We use an orbital model initially developed by Ronnet et al. (2018) [8] to investigate the injection of planetesimals into the asteroid belt following giant planet growth in the protoplanetary disk (PSD). We conduct simulations using REBOUND, consisting of 20,000 test particles each, representing 100-km-sized planetesimals. Our five-planet model, inspired by the works of Nesvorn&#253; et al. (2015) [9] and Dienno et al. (2017) [10], features Jupiter, Saturn, an additional ice giant (commonly ejected from the solar system), Uranus, and Neptune. Initially, planets are located on low-eccentricity orbits, with Jupiter at 5.4 au and Saturn at the edge of its gap, at 7.3 au. We choose to neglect the influence of the telluric planets, which, having relatively small orbits, require more computation time. We place Neptune in two different configurations: a 'tight' configuration at 16.2 au, in a 3:2, 3:2, 3:2, 3:2 resonance chain, and a 'wide' configuration at 20.3 au, in a 3:2, 3:2, 2:1, 3:2 resonance chain. The test particles' semi-major axes are initialized uniformly between 7 au and 1 au beyond the orbit of Neptune. We examine the effects of gas profile (&#931;g), planetary growth timescale (&#964;growth), and the viscosity parameter (&#945;) on the distribution of planetesimals implanted in the asteroid belt. Notably, we investigate three different gas profiles: the traditional canonical model with a radial dependency of &#931;g &#8733; r&#8722;0.5 [11], the Desch et al. 2018 model [12], and the Raymond &amp; Izidoro 2017 model [3].This study's findings aim to contribute significantly to our understanding of the dynamic processes that shaped the early solar system and the specific pathways that led to the observed dichotomy&#8212;or trichotomy&#8212;in carbonaceous chondrite composition. By comparing the outcomes of our simulations with existing data, we anticipate providing new insights into the ongoing debate over the formational contexts of these asteroids, thereby enhancing the broader astrophysical models concerning planetary formation and migration.Figure 1: Distinct spectral classifications (CM, CI/IDP, S) reveal systematic differences in the distributions of main-belt asteroids with D>100 km.

[1] A. Morbidelli et al., Chaotic capture of Jupiter&#8217;s Trojan asteroids in the early Solar System, 435.7041 (May 2005), pp. 462&#8211;465.[2] Kevin J. Walsh et al., A low mass for Mars from Jupiter&#8217;s early gas-driven migration, 475.7355 (July 2011), pp. 206&#8211;209.[3] Sean N. Raymond and Andre Izidoro, Origin of water in the inner Solar System: Planetesimals scattered inward during Jupiter and Saturn&#8217;s rapid gas accretion, 297 (Nov. 2017), pp. 134&#8211;148.[4] Timo Hopp et al., Ryugu&#8217;s nucleosynthetic heritage from the outskirts of the Solar System, Science Advances 8.46 (2022), eadd8141.[5] Toru Yada et al., Preliminary analysis of the Hayabusa2 samples returned from C-type asteroid Ryugu, Nature Astronomy 6 (Dec. 2021), pp. 214&#8211;220.[6] Tetsuya Yokoyama et al., Samples returned from the asteroid Ryugu are similar to Ivuna-type carbonaceous meteorites, Science 379.6634 (2023), eabn7850.[7] P. Vernazza et al., VLT/SPHERE imaging survey of the largest main belt asteroids: Final results and synthesis, 654, A56 (Oct. 2021), A56.[8] T. Ronnet et al., Saturn&#8217;s Formation and Early Evolution at the Origin of Jupiter&#8217;s Massive Moons, 155.5, 224 (May 2018), p. 224.[9] David Nesvorn&#253;, Evidence for slow migration of Neptune from the inclination distribution of Kuiper Belt objects, The Astronomical Journal 150.3 (Aug. 2015), p. 73.[10] Rogerio Deienno et al., Constraining the Giant Planets&#8217; Initial Configuration from Their Evolution: Implications for the Timing of the Planetary Instability, 153.4, 153 (Apr. 2017), p. 153.[11] P. Cresswell and R. P. Nelson, Three-dimensional simulations of multiple protoplanets embedded in a protostellar disc, 482.2 (May 2008), pp. 677&#8211;690.[12] Steven J. Desch, Anusha Kalyaan, and Conel M. O&#8217;D. Alexander, The Effect of Jupiter&#8217;s Formation on the Distribution of Refractory Elements and Inclusions in Meteorites, The Astrophysical Journal Supplement Series 238.1 (Sept. 2018), p. 11.
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