Formation and Accretion History of Terrestrial Planets from Runaway Growth through to Late Time: Implications for Orbital Eccentricity

Morishima, Ryuji; Schmidt, Max W.; Stadel, Joachim; Moore, Ben

doi:10.1086/590948

Cited by 78 publications

(79 citation statements)

References 50 publications

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“…However, the radial concentration of planetary mass seen in our own solar system can be replicated if terrestrial planet formation begins from a narrow annulus ( Figure 3) (Morishima et al 2008;Hansen 2009). We mimic this in our last ensemble, "annulus" (ANN).…”

Section: Methodsmentioning

confidence: 74%

The feeding zones of terrestrial planets and insights into Moon formation

Kaib

Cowan

2015

Icarus

105

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The final stage of terrestrial planet formation consists of several hundred approximately lunar mass bodies accreting into a few terrestrial planets. This final stage is stochastic, making it hard to predict which parts of the original planetesimal disk contributed to each of our terrestrial planets. Here we present an extensive suite of terrestrial planet formation simulations that allows quantitative analysis of this process. Although there is a general correlation between a planet's location and the initial semi-major axes of its constituent planetesimals, we concur with previous studies that Venus, Earth, and Mars analogs have overlapping, stochastic feeding zones. We quantify the feeding zone width, ∆a, as the mass-weighted standard deviation of the initial semi-major axes of the planetary embryos and planetesimals that make up the final planet. The size of a planet's feeding zone in our simulations does not correlate with its final mass or semi-major axis, suggesting there is no systematic trend between a planet's mass and its volatile inventory. Instead, we find that the feeding zone of any planet more massive than 0.1M ⊕ is roughly proportional to the radial extent of the initial disk from which it formed: ∆a ≈ 0.25(a max − a min ), where a min and a max are the inner and outer edge of the initial planetesimal disk. These wide stochastic feeding zones have significant consequences for the origin of the Moon, since the canonical scenario predicts the Moon should be primarily composed of material from Earth's last major impactor (Theia), yet its isotopic composition is indistinguishable from Earth. In particular, we find that the feeding zones of Theia analogs are significantly more stochastic than the planetary analogs. Depending on our assumed initial distribution of oxygen isotopes within the planetesimal disk, we find a ∼5% or less probability that the Earth and Theia will form with an isotopic difference equal to or smaller than the Earth and Moon's. In fact we predict that every planetary mass body should be expected to have a unique isotopic signature. In addition, we find paucities of massive Theia analogs and high velocity moon-forming collisions, two recently proposed explanations for the Moon's isotopic composition. Our work suggests that there is still no scenario for the Moon's origin that explains its isotopic composition with a high probability event.

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Section: Methodsmentioning

confidence: 74%

The feeding zones of terrestrial planets and insights into Moon formation

Kaib

Cowan

2015

Icarus

105

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“…The terrestrial planets have low eccentricities and inclinations, Earth and Venus both have e < 0.02 and i < 3 • , properties which has proved difficult to match in accretion simulations. O'Brien et al (2006) and Morishima et al (2008) reproduced low eccentricities and inclinations largely due to remaining planetesimals which damp the orbital excitation of the planets. A metric used as a diagnostic of the degree of success of the simulations in reproducing the dynamical excitation of the terrestrial planets is the angular momentum deficit (AMD; Laskar 1997):…”

Section: The Planetsmentioning

confidence: 97%

The effect of an early planetesimal-driven migration of the giant planets on terrestrial planet formation

Walsh

Morbidelli

2011

A&A

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The migration of the giant planets due to the scattering of planetesimals causes powerful resonances to move through the asteroid belt and the terrestrial planet region. Exactly when and how the giant planets migrated is not well known. In this paper we present results of an investigation of the formation of the terrestrial planets during and after the migration of the giant planets. The latter is assumed to have occurred immediately after the dissipation of the nebular disk -i.e. "early" with respect to the timing of the late heavy bombardment (LHB). The presumed cause of our modeled early migration of the giant planets is angular mometum transfer between the planets and scattered planetesimals. Our model forms the terrestrial planets from a disk of material which stretchs from 0.3-4.0 AU, evenly split in mass between planetesimals and planetary embryos. Jupiter and Saturn are initially at 5.4 and 8.7 AU respectively, on orbits with eccentricities comparable to the current ones, and migrate to 5.2 and 9.4 AU with an e-folding time of 5 Myr. Unfortunately, the terrestrial planets formed in the simulations are not good analogs for the current solar system, with Mars typically being much too massive. Moreover, the final distribution of the planetesimals remaining in the asteroid belt is inconsistent with the observed distribution of asteroids. This argues that, even if giant planet migration had occurred early, the real evolution of the giant planets would have to have been of the "jumping-Jupiter" type, i.e. the increase in orbital separation between Jupiter and Saturn had to be dominated by encounters between Jupiter and a third, Neptune-mass planet. This result was already demonstrated for late migrations occuring at the LHB time by previous work, and this paper shows those conclusions hold for early migration as well.

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“…The radial mass concentration of the solar system's terrestrial planets is S c = 89.9, which indicates high radial mass concentration because the masses of Mercury and Mars are small and the orbital distance between Venus and the Earth is also relatively small. Previous studies have shown that it is difficult to reproduce such a high mass concentration (e.g., Raymond et al 2009;Morishima et al 2010); a way to account for this statistic in N-body simulations is to assume a mass distribution initially confined to a narrow annulus (Morishima et al 2008;Hansen 2009), or in other words to assume an initially large S c . In the grand tack model (e.g., Walsh et al 2011;, Jupiter sweeps up to ∼1.5 AU and embryos are eventually confined to a relatively compact region.…”

Section: Origin Of the Solar System's Terrestrial Planetsmentioning

confidence: 99%

Formation of terrestrial planets in disks evolving via disk winds and implications for the origin of the solar system’s terrestrial planets

Ogihara

Kobayashi

Inutsuka

et al. 2015

A&A

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Context. Recent three-dimensional magnetohydrodynamical simulations have identified a disk wind by which gas materials are lost from the surface of a protoplanetary disk, which can significantly alter the evolution of the inner disk and the formation of terrestrial planets. A simultaneous description of the realistic evolution of the gaseous and solid components in a disk may provide a clue for solving the problem of the mass concentration of the terrestrial planets in the solar system. Aims. We simulate the formation of terrestrial planets from planetary embryos in a disk that evolves via magnetorotational instability and a disk wind. The aim is to examine the effects of a disk wind on the orbital evolution and final configuration of planetary systems. Methods. We perform N-body simulations of sixty 0.1 Earth-mass embryos in an evolving disk. The evolution of the gas surface density of the disk is tracked by solving a one-dimensional diffusion equation with a sink term that accounts for the disk wind. Results. We find that even in the case of a weak disk wind, the radial slope of the gas surface density of the inner disk becomes shallower, which slows or halts the Type I migration of embryos. If the effect of the disk wind is strong, the disk profile is significantly altered (e.g., positive surface density gradient, inside-out evacuation), leading to outward migration of embryos inside ∼1 AU. Conclusions. Disk winds play an essential role in terrestrial planet formation inside a few AU by changing the disk profile. In addition, embryos can undergo convergent migration to ∼1 AU in certainly probable conditions. In such a case, the characteristic features of the solar system's terrestrial planets (e.g., mass concentration around 1 AU, late giant impact) may be reproduced.

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Formation and Accretion History of Terrestrial Planets from Runaway Growth through to Late Time: Implications for Orbital Eccentricity

Cited by 78 publications

References 50 publications

The feeding zones of terrestrial planets and insights into Moon formation

The feeding zones of terrestrial planets and insights into Moon formation

The effect of an early planetesimal-driven migration of the giant planets on terrestrial planet formation

Formation of terrestrial planets in disks evolving via disk winds and implications for the origin of the solar system’s terrestrial planets

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