Asteroids Were Born Big

By A. Morbidelli, William Bottke, D. Nesvorný, Harold Levison. 2009

427 citations recorded by the source corpus.

Abstract How big were the first planetesimals? We attempt to answer this question by conducting coagulation simulations in which the planetesimals grow by mutual collisions and form larger bodies and planetary embryos. The size frequency distribution (SFD) of the initial planetesimals is considered a free parameter in these simulations, and we search for the one that produces at the end objects with a SFD that is consistent with Asteroid belt constraints. We find that, if the initial planetesimals were small (e.g. km-sized), the final SFD fails to fulfill these constraints. In particular, reproducing the bump observed at diameter D ∼ 100 km in the current SFD of the asteroids requires that the minimal size of the initial planetesimals was also ∼100 km. This supports the idea that planetesimals formed big, namely that the size of solids in the proto-planetary disk “jumped” from sub-meter scale to multi-kilometer scale, without passing through intermediate values. Moreover, we find evidence that the initial planetesimals had to have sizes ranging from 100 to several 100 km, probably even 1000 km, and that their SFD had to have a slope over this interval that was similar to the one characterizing the current asteroids in the same size range. This result sets a new constraint on planetesimal formation models and opens new perspectives for the investigation of the collisional evolution in the Asteroid and Kuiper belts as well as of the accretion of the cores of the giant planets.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/39c698405af86bc3ef971dfbbd21cb115e820d2b

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Citations in the corpus

Rubble Pile Asteroids (2018, background): “4; Bottke et al. 2005,2015; Morbidelli et al. 2009).”
Rapid growth of gas-giant cores by pebble accretion (2012, background): “Additionally, studies of the collisional evolution of the asteroid belt show that large asteroids must have formed early when gas was still present (Morbidelli et al. 2009).”
Building Terrestrial Planets (2012, background): “The size distribution of objects in the asteroid belt and in the Kuiper belt, where most of the mass is concentrated in 100-km objects, supports this scenario (Morbidelli et al. 2009; but see Weidenschilling 2010).”
FORMATION OF KUIPER BELT BINARIES BY GRAVITATIONAL COLLAPSE (2010, background): “Indeed, constraints from the Size Frequency Distribution (SFD) of main-belt asteroids indicate that the standard hierarchical coagulation was not the driving force of planetesimal accretion at 2-4 AU (Morbidelli et al. 2009).”
The great dichotomy of the Solar System: Small terrestrial embryos and massive giant planet cores (2015, background): “For a disk of equal mass particles, the growth rate of the eccentricity dispersion is (Stewart and Ida, 2000; Morbidelli et al., 2009 - supplementary material): de2 dt ∝ ρpM V 3Ke , (5) where M is the individual mass of the planetesimals and VK is the keplerian velocity.”
Prograde rotation of protoplanets by accretion of pebbles in a gaseous environment (2009, background): “These objects have thus likely retained their primordial spin angular momentum and may be representative of the original protoplanet population (see also Morbidelli et al. 2009).”
How to form planetesimals from mm-sized chondrules and chondrule aggregates (2015, background): “Therefore, it appears that the size of solids in the protoplanetary disk “jumped” from the submeter scale to ∼100 km without passing through the intermediate sizes, and that bodies smaller than 100 km formed later by collisional grinding (Morbidelli et al. 2009).”
Adding particle collisions to the formation of asteroids and Kuiper belt objects via streaming instabilities (2011, background): “…picture of the planetesimal formation stage, and at the same time it gives insight into the physical processes that shaped the architectures of these systems (Morbidelli et al. 2009; Weidenschilling 2010; Nesvorný et al. 2010; Sheppard & Trujillo 2010; Krivov 2010; Kenyon & Bromley 2010).”
The Effect of Jupiter's Formation on the Distribution of Refractory Elements and Inclusions in Meteorites (2017, background): “…of material is a commonly invoked concept in meteoritics (Wood 2005), and is given strong support by models of rapid planet growth (e.g., streaming instability: Johansen et al. 2007; and pebble accretion: Lambrechts et al. 2014) and the size distribution of asteroids (Morbidelli et al. 2009).”
Differentiated Planetesimals and the Parent Bodies of Chondrites (2013, background): “…of clumps of centimeter- to meter-sized objects concentrated by streaming instabilities or by turbulent eddies into 10- to >100-km-sized solid bodies on timescales of just tens to hundreds of years in the asteroid belt region (Cuzzi et al. 2008, Johansen et al. 2007, Morbidelli et al. 2009).”
Origin of water in the inner Solar System: Planetesimals scattered inward during Jupiter and Saturn's rapid gas accretion (2017, background): “Several different initial asteroid size distributions have been proposed (Morbidelli et al., 2009; Weidenschilling, 2011; Johansen et al., 2015).”
Density of asteroids (2012, result): “This is consistent with the current vision of the dynamical history of the Main Belt: large asteroids survived intact throughout the history of the Solar System, while most of the material was removed or grinded into pieces (Morbidelli et al., 2009).”
THE CANADA–FRANCE ECLIPTIC PLANE SURVEY—L3 DATA RELEASE: THE ORBITAL STRUCTURE OF THE KUIPER BELT (2009, background): “This may not be impossible due to recent work on forming planetesimals736 big (Morbidelli et al. 2009a; Youdin 2011), which can be favored by external photoevaporation (Throop &737 Bally 2005), and may be supported by the fact that it appears that there are simply no cold objects larger738 thanH ∼…”