Feedstocks of the Terrestrial Planets

Carlson, Richard W.; Brasser, R.; Yin, Qing‐Zhu; Fischer-Gödde, M.; Qin, Liping

doi:10.1007/s11214-018-0554-x

Cited by 21 publications

(18 citation statements)

References 169 publications

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“…This rapid accretion is difficult to reconcile with current dynamical and Hf-W chronometry models (e.g. Carlson et al, 2018;Yu and Jacobson, 2011).…”

Section: Accretion Rates Of Inner Disk Mass Versus Time Obtained Frommentioning

confidence: 91%

Formation of Venus, Earth and Mars: Constrained by Isotopes

et al. 2020

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Here we discuss the current state of knowledge of terrestrial planet formation from the aspects of different planet formation models and isotopic data from 182 Hf-182 W, U-Pb, lithophile-siderophile elements, 48 Ca/ 44 Ca isotope samples from planetary building blocks, recent reproduction attempts from 36 Ar/ 38 Ar, 20 Ne/ 22 Ne, 36 Ar/ 22 Ne isotope ratios in Venus' and Earth's atmospheres, the expected solar 3 He abundance in Earth's deep mantle and Earth's D/H sea water ratios that shed light on the accretion time of the early protoplanets. Accretion scenarios that can explain the different isotope ratios, including a Moon-forming event ca. 50 Myr after the formation of the Solar System, support the theory that the bulk of Earth's mass (≥ 80 %) most likely accreted within 10-30 Myr. From a combined analysis of the before mentioned isotopes, one finds that proto-Earth accreted a mass of 0.5-0.6 MEarth within the first ≈ 4-5 Myr, the approximate lifetime of the protoplanetary disk. For Venus, the available atmospheric noble gas data are too uncertain for constraining the planet's accretion scenario accurately. However, from the available imprecise Ar and Ne isotope measurements, one finds that proto-Venus could have grown to a mass of 0.85-1.0 MVenus before the disk dissipated. Classical terrestrial planet formation models have struggled to grow large planetary embryos, or even cores of giant planets, quickly from the tiniest materials within the typical lifetime of protoplanetary disks. Pebble accretion could solve this long-standing time scale controversy. Pebble accretion and streaming instabilities produce large planetesimals that grow into Marssized and larger planetary embryos during this early accretion phase. The later stage of accretion can be explained well with the Grand-Tack model as well as the annulus and depleted disk models. The relative roles of pebble accretion and planetesimal accretion/giant impacts are poorly understood and should be investigated with N-body simulations that include pebbles and multiple protoplanets. To summarise, different isotopic dating methods and the latest terrestrial planet formation models indicate that the accretion process from dust settling, planetesimal formation, and growth to large planetary embryos and protoplanets is a fast process that occurred to a great extent in the Solar System within the lifetime of the protoplanetary disk.

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“…This rapid accretion is difficult to reconcile with current dynamical and Hf-W chronometry models (e.g. Carlson et al, 2018;Yu and Jacobson, 2011).…”

Section: Accretion Rates Of Inner Disk Mass Versus Time Obtained Frommentioning

confidence: 91%

Formation of Venus, Earth and Mars: Constrained by Isotopes

et al. 2020

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“…-Hungaria: 1.7 au < a f < 2.1 au -Vesta: 2.1 au < a f < 2.5 au -Hebe: 2.2 au < a f < 2.6 au We find that for the Grand Tack model, planetary embryos constitute 2% of the total number of asteroid analogues that end up in the disc regions of interest defined above while the fraction is 0.9% for the EJS model and 0.3% for the depleted disc model. The fraction of planetary embryos that end up in the region beyond 1.7 au is highest for the Grand Tack model because Jupiter and Saturn's migration reshuffles the orbits of the solid material in the disc (Carlson et al 2018). We included all objects (planetary embryos and planetesimals) in the analysis of this work.…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, the observed differences in the isotopic compositions of Earth, Mars, asteroid Vesta (and possibly asteroids Hungaria and Hebe) suggest that there are differences in the compositions of their building blocks which would imply formation at various locations throughout the disc (e.g. Carlson et al 2018;Mezger et al 2020). It is worth noting, however, that at the present time no cosmochemical model can simultaneously account for both the bulk and isotopic compositions of the planets and the different meteorite groups by any mixing model of the known components.…”

Section: Introductionmentioning

confidence: 99%

“…The main reason for this outcome is the migration of the gas giants. Jupiter and Saturn's excursion through the asteroid belt region excited the orbits of the material in the terrestrial planet region and caused them to undergo mixing (Carlson et al 2018). If there was a difference in the composition of the material in the terrestrial planet region, it is expected that this difference would have been homogenised.…”

Section: Introductionmentioning

confidence: 99%

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Evidence of a primordial isotopic gradient in the inner region of the solar protoplanetary disc

Mah,

Brasser,

Woo

et al. 2022

Preprint

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Not only do the sampled terrestrial worlds (Earth, Mars and asteroid 4 Vesta) differ in their mass-independent (nucleosynthetic) isotopic compositions for many elements (e.g. ε 48 Ca, ε 50 Ti, ε 54 Cr, ε 92 Mo), the magnitude of some of these isotopic anomalies also appear to correlate with heliocentric distance. While the isotopic differences between the Earth and Mars may be readily accounted for by the accretion of mostly local materials in distinct regions of the protoplanetary disc, it is unclear whether this applies also to asteroid Vesta. Here we analysed available data from our numerical simulation database to determine the formation location of Vesta in the framework of three planet-formation models: classical, Grand Tack, and Depleted Disc. We find that Vesta has a high probability of forming locally in the asteroid belt in models where material mixing in the inner disc is limited; this limited mixing is implied by the isotopic differences between the Earth and Mars. Based on our results, we propose several criteria to explain the apparent correlation between the different nucleosynthetic isotopic compositions of the Earth, Mars and Vesta: (1) these planetary bodies accreted their building blocks in different regions of the disc, (2) the inner disc is characterised by an isotopic gradient, and (3) the isotopic gradient was preserved during the formation of these planetary bodies and was not diluted by material mixing in the disc (e.g. via giant planet migration).

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“…As a result, the oxygen isotope compositions are expected to be scattered between fractionation lines of different building blocks if the accretion timescale τ is greater than ∼1 Myr. We assume that the building blocks consist of enstatite chondrite (fractionation line indicated in blue) and ordinary chondrite (fractionation line indicated in red), as suggested for Mars (e.g., Carlson et al., 2018), and predict that samples would plot in the gray area in (b). Moreover, silicate differentiation occurred before the extinction of 26 Al (regardless of τ ), and this early differentiation would lead to substantial variation in μ 53 Cr (the decay product of 53 Mn with half‐life 3.7 Myr), as indicated by the gray region in (c) (Kruijer et al., 2020).…”

Section: Implications For the Formation Of Marsmentioning

confidence: 99%

A Two‐Phase Model for the Evolution of Planetary Embryos With Implications for the Formation of Mars

2021

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The formation of terrestrial planets is typically viewed as a play in three acts (e.g., Jacobson & Walsh, 2015;Morbidelli et al., 2012). First, planetesimals were formed in a disk of gas and dust in a few hundred thousand years. Second, Moon-to Mars-sized planetary embryos were generated by collisions of planetesimals or accretion of submeter-scale "pebbles" over the next few million years. Lastly, Earth-sized terrestrial planets were produced by giant impacts between planetary embryos in ten to a hundred million years.As one of the four major celestial bodies of the inner solar system, Mars provides an important sample for studies on planetary formation processes. Mars could be either a large stranded "planetary embryo" (i.e., product of the second act that formed early through gradual accretion and remained isolated afterward) or a small "planet" (i.e., product of the final act that underwent protracted accretion through catastrophic giant impacts). As these two scenarios are preferred by different conditions of the proto-planetary disk from

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Feedstocks of the Terrestrial Planets

Cited by 21 publications

References 169 publications

Formation of Venus, Earth and Mars: Constrained by Isotopes

Formation of Venus, Earth and Mars: Constrained by Isotopes

Evidence of a primordial isotopic gradient in the inner region of the solar protoplanetary disc

A Two‐Phase Model for the Evolution of Planetary Embryos With Implications for the Formation of Mars

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