Onset of oligarchic growth and implication for accretion histories of dwarf planets

Morishima, Ryuji

doi:10.1016/j.icarus.2016.07.019

Cited by 31 publications

(11 citation statements)

References 89 publications

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“…Latest estimates of the initial size frequency distribution of planetesimals from the streaming instability mechanism (Johansen et al, 2015;Simon et al, 2016Simon et al, , 2017 converge on a power law dN/dR P ∼ R −q P , with the number of bodies N, the planetesimal radius R P , index q = 2.8 and without an obvious lower cut-off. These estimates are consistent with the current distribution in the asteroid belt if accretional growth of small bodies via collisions and/or pebble accretion is consid-ered (Weidenschilling, 2011;Lithwick, 2014;Johansen et al, 2015;Morishima, 2017). In such a birth-SFD, the bulk of the mass resides in massive planetesimals, while the absolute number of low-mass planetesimals exceeds the number of massive bodies by orders of magnitude.…”

Section: Accretion and Dynamical Recyclingsupporting

confidence: 82%

“…We have sketched one such accretion-collision cycle to generate chondrules in Figure 11. In the future, the dynamical feasibility and implications of our proposed chondrule formation scenario can be explored with astrophysical models that simultaneously solve for a global planetesimal source system and achieve sufficiently high mass resolution to resolve the low-mass bodies we focused on in this work (e.g., Levison et al, 2012;Morishima, 2017).…”

Section: Discussionmentioning

confidence: 99%

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Impact splash chondrule formation during planetesimal recycling

Lichtenberg

Golabek

Dullemond

et al. 2018

Icarus

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Chondrules, mm-sized igneous-textured spherules, are the dominant bulk silicate constituent of chondritic meteorites and originate from highly energetic, local processes during the first million years after the birth of the Sun. So far, an astrophysically consistent chondrule formation scenario explaining major chemical, isotopic and textural features, in particular Fe,Ni metal abundances, bulk Fe/Mg ratios and intra-chondrite chemical and isotopic diversity, remains elusive. Here, we examine the prospect of forming chondrules from impact splashes among planetesimals heated by radioactive decay of short-lived radionuclides using thermomechanical models of their interior evolution. We show that intensely melted planetesimals with interior magma oceans became rapidly chemically equilibrated and physically differentiated. Therefore, collisional interactions among such bodies would have resulted in chondrule-like but basaltic spherules, which are not observed in the meteoritic record. This inconsistency with the expected dynamical interactions hints at an incomplete understanding of the planetary growth regime during the lifetime of the solar protoplanetary disk. To resolve this conundrum, we examine how the observed chemical and isotopic features of chondrules constrain the dynamical environment of accreting chondrite parent bodies by interpreting the meteoritic record as an impact-generated proxy of early solar system planetesimals that underwent repeated collision and reaccretion cycles. Using a coupled evolution-collision model we demonstrate that the vast majority of collisional debris feeding the asteroid main belt must be derived from planetesimals which were partially molten at maximum. Therefore, the precursors of chondrite parent bodies either formed primarily small, from sub-canonical aluminum-26 reservoirs, or collisional destruction mechanisms were efficient enough to shatter planetesimals before they reached the magma ocean phase. Finally, we outline the window in parameter space for which chondrule formation from planetesimal collisions can be reconciled with the meteoritic record and how our results can be used to further constrain early solar system dynamics.

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Section: Accretion and Dynamical Recyclingsupporting

confidence: 82%

Section: Discussionmentioning

confidence: 99%

Impact splash chondrule formation during planetesimal recycling

Lichtenberg

Golabek

Dullemond

et al. 2018

Icarus

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“…Studies of the runaway and oligarchic regimes have been also conducted in different fronts. This includes N-body simulations (Ida and Makino 1993;Aarseth et al 1993;Kokubo and Ida 1996Richardson et al 2000;Thommes et al 2003;Barnes et al 2009), analytical/semi-analytical calculations based on statistical algorithms (Greenberg et al 1978;Wetherill and Stewart 1989;Rafikov 2003c,b,a;Goldreich et al 2004;Kenyon and Bromley 2004;Ida and Lin 2004;Chambers 2006;Morbidelli et al 2009;Schlichting and Sari 2011;Schlichting et al 2013), hybrid statistical/N-body (or N-body coagulation) codes which incorporates the two latter approaches (Spaute et al 1991;Weidenschilling et al 1997;Ormel et al 2010b;Bromley and Kenyon 2011;Glaschke et al 2014), and finally the more recently developed hybrid particle-based algorithms (Levison et al 2012;Morishima 2015Morishima , 2017.…”

Section: Methods and Numerical Toolsmentioning

confidence: 99%

Formation of Terrestrial Planets

Izidoro¹,

Raymond²

2018

Handbook of Exoplanets

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The past decade has seen major progress in our understanding of terrestrial planet formation. Yet key questions remain. In this review we first address the growth of 100 km-scale planetesimals as a consequence of dust coagulation and concentration, with current models favoring the streaming instability. Planetesimals grow into Mars-sized (or larger) planetary embryos by a combination of pebbleand planetesimal accretion. Models for the final assembly of the inner Solar System must match constraints related to the terrestrial planets and asteroids including their orbital and compositional distributions and inferred growth timescales. Two current models -the Grand-Tack and low-mass (or empty) primordial asteroid belt scenarios -can each match the empirical constraints but both have key uncertainties that require further study. We present formation models for close-in super-Earthsthe closest current analogs to our own terrestrial planets despite their very different formation histories -and for terrestrial exoplanets in gas giant systems. We explain why super-Earth systems cannot form in-situ but rather may be the result of inward gas-driven migration followed by the disruption of compact resonant chains. The Solar System is unlikely to have harbored an early system of super-Earths; rather, Jupiter's early formation may have blocked the ice giants' inward migration. Finally, we present a chain of events that may explain why our Solar System looks different than more than 99% of exoplanet systems.

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“…The slopes formed via runaway growth is roughly explained by gravitational focusing and dynamical friction. In more detailed analysis, the runaway-growth slopes bend slightly (see Morishima 2017).…”

Section: Size and Velocity Distributions Around 5 Aumentioning

confidence: 99%

From Planetesimal to Planet in Turbulent Disks. II. Formation of Gas Giant Planets

Kobayashi

Tanaka

2018

ApJ

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In the core accretion scenario, gas giant planets are formed form solid cores with several Earth masses via gas accretion. We investigate the formation of such cores via collisional growth from kilometersized planetesimals in turbulent disks. The stirring by forming cores induces collisional fragmentation and surrounding planetesimals are ground down until radial drift. The core growth is therefore stalled by the depletion of surrounding planetesiamls due to collisional fragmentation and radial drift. The collisional strength of planetesimals determines the planetesimal-depletion timescale, which is prolonged for large planetesiamls. The size of planetesiamls around growing cores is determined by the planetesimal size distribution at the onset of runaway growth. Strong turbulence delays the onset of runaway growth, resulting in large planetesimals. Therefore, the core mass evolution depends on turbulent parameter α; the formation of cores massive enough without significant depletion of surrounding planetesimals needs strong turbulence of α 10 −3 . However, the strong turbulence with α 10 −3 leads to a significant delay of the onset of runaway growth and prevents the formation of massive cores within the disk lifetime. The formation of cores massive enough within several millions years therefore requires the several times enhancement of the solid surface densities, which is achieved in the inner disk 10AU due to pile-up of drifting dust aggregates. In addition, the collisional strength Q * D even for kilometer-sized or smaller bodies affects the growth of cores; Q * D 10 7 erg/g for bodies 1 km is likely for this gas giant formation.

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Onset of oligarchic growth and implication for accretion histories of dwarf planets

Cited by 31 publications

References 89 publications

Impact splash chondrule formation during planetesimal recycling

Impact splash chondrule formation during planetesimal recycling

Formation of Terrestrial Planets

From Planetesimal to Planet in Turbulent Disks. II. Formation of Gas Giant Planets

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