Compositions of carbonaceous-type asteroidal cores in the early solar system

Zhang, Bidong; Chabot, N. L.; Rubin, Alan E.

doi:10.1126/sciadv.abo5781

Cited by 12 publications

(23 citation statements)

References 65 publications

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“…This link is important because such regular CAIs are thought to have formed close to the Sun (<1 AU; Bekaert et al, 2021) in a geologically brief window of time (<200,000 years; Connelly et al, 2017;Kawasaki et al, 2019;MacPherson et al, 2012), and their presence in a meteorite that formed distally in the solar system at ~3.5 Myr (Sugiura & Fujiya, 2014) provides some of the first quantitative constraints on the time scales and distances of the transport of millimeterscale material in the early solar system. This is consistent with the more recent notion that CAIs were already present in the CC region prior to achondrite (Render et al, 2022) and iron meteorite (Zhang et al, 2022) formation (i.e., <1 Myr after solar system formation). Taking the conservatively approximated values of 0.5 AU for CAI formation and 3.5 Myr after CAI formation for the accretion of the WIS 91600 parent body at 9.8 AU, we calculate a first-order approximation of the transport speed of millimeter-scale objects in the early protoplanetary disk of ~400 km year −1 .…”

Section: Implications For Solar System Transport Processessupporting

confidence: 92%

Disk transport rates from Ti isotopic signatures of refractory inclusions

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Bryson

Ebert

et al. 2022

Meteorit & Planetary Scien

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The early solar system was a dynamic period during which the formation of early solids set into motion the process of planet building. Although both astrophysical observations and theoretical modeling demonstrate the presence of widespread transport of material, we lack concrete quantitative constraints on timings, distances, and mechanisms thereof. To trace these transport processes, one needs objects of known early formation times and these objects would need to be distributed throughout parent bodies with known accretion times and distances. Generally, these criteria are met by “regular” (i.e., non–fractionated and unidentified nuclear and excluding hibonite‐rich) Ca‐Al‐rich inclusions (CAIs) as these objects formed very early and close to the young Sun and contain distinctive nucleosynthetic isotope anomalies that permit provenance tracing. However, nucleosynthetic isotopic signatures of such refractory inclusions have so far primarily been analyzed in chondritic meteorites that formed within ~4 AU from the Sun. Here, we investigate Ti isotopic signatures of four refractory inclusions from the ungrouped carbonaceous chondrite WIS 91600 that was previously suggested to have formed beyond ~10 AU from the Sun. We show that these inclusions exhibit correlated excesses in 50Ti and 46Ti and lack large Ti isotopic anomalies that would otherwise be indicative of more enigmatic refractory materials with unknown formation ages. Instead, these isotope systematics suggest the inclusions to be genetically related to regular CAIs commonly found in other chondrites that have a broadly known formation region and age. Collectively, this implies that a common population of CAIs was distributed over the inner ~10 AU within ~3.5 Myr, yielding an average (minimum) speed for the transport of millimeter‐scale material in the early solar system of ~1 cm s−1.

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Section: Implications For Solar System Transport Processessupporting

confidence: 92%

Disk transport rates from Ti isotopic signatures of refractory inclusions

Render

Bryson

Ebert

et al. 2022

Meteorit & Planetary Scien

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“…ALHA77255 is excluded in the modeling test because its Au/As ratio (0.23) is significantly lower than those of the other three irons (0.34 ± 0.05). For irons from a single parent melt, their Au/As ratios should be consistent (Zhang et al., 2022a, 2022b). The Ir‐As trend of Nordheim, Babb's Mill (Blake's Iron), and Chinga does not conform to the fractional crystallization trends (Fig.…”

Section: Resultsmentioning

confidence: 99%

Impact‐induced devolatilization of four ungrouped ataxites and the formation of a silica glass spherule in ALHA77255

Rubin

Zhang

2022

Meteorit & Planetary Scien

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Allan Hills A77255, Babb's Mill (Blake's Iron), Nordheim, and Chinga are ungrouped ataxitic iron meteorites that are similar to the IAB group of noncarbonaceous‐type irons in their concentrations of common and refractory siderophile elements. Mo‐isotopic data show that ALHA77255, Nordheim, and Chinga are carbonaceous‐type (CC) irons. (The Mo‐isotopic composition of Babb's Mill [Blake's Iron] has not yet been measured, but it also seems likely to be a CC iron.) Relative to mean IAB irons, these four ataxites are severely depleted in moderately volatile elements: Ga, >99%; Ge, >99%; Cu, 79%–97%; As, 70%–96%; P, 76%–90%. These samples were probably devolatilized by major collisions on separate parent asteroids (consistent with fractional crystallization modeling showing they are unlikely to be derived from the same metallic core). Collisionally induced devolatilization of ALHA77255 likely facilitated the formation of a 5‐mm diameter silica–glass spheroid in this meteorite. The spheroid may have formed by a complex process involving impact‐induced vaporization of mantle material in its parent asteroid, followed by fractional condensation.

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“…Our previous study ( 44 ) also showed that the CAI distribution in the outer disk at <1 Ma was heterogeneous. The precursor materials of CC magmatic iron-meteorite parent bodies had varying CAI modal abundances (0 to 26 wt.%) ( 44 ), indicating the heterogeneous distribution of CAIs in the nebula predated the agglomeration of chondrites.…”

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confidence: 75%

“…The bulk compositions and crystallization processes of these asteroidal cores can be reconstructed using fractional-crystallization modeling ( 23 , 26 – 28 ), but previous studies focused on a few elements among groups or on many elements within a single group ( 29 – 43 ). Zhang et al ( 44 ) were the first to examine many elements (up to 19) for all CC-iron groups in a single study. Their preliminary conclusion was that the CC-iron cores had more efficient convection, elevated highly siderophile-element (HSE) abundances, and lower bulk S contents.…”

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confidence: 99%

Compositions of iron-meteorite parent bodies constrain the structure of the protoplanetary disk

Zhang,

Chabot,

Rubin

2024

Proc. Natl. Acad. Sci. U.S.A.

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Magmatic iron-meteorite parent bodies are the earliest planetesimals in the Solar System, and they preserve information about conditions and planet-forming processes in the solar nebula. In this study, we include comprehensive elemental compositions and fractional-crystallization modeling for iron meteorites from the cores of five differentiated asteroids from the inner Solar System. Together with previous results of metallic cores from the outer Solar System, we conclude that asteroidal cores from the outer Solar System have smaller sizes, elevated siderophile-element abundances, and simpler crystallization processes than those from the inner Solar System. These differences are related to the formation locations of the parent asteroids because the solar protoplanetary disk varied in redox conditions, elemental distributions, and dynamics at different heliocentric distances. Using highly siderophile-element data from iron meteorites, we reconstruct the distribution of calcium-aluminum-rich inclusions (CAIs) across the protoplanetary disk within the first million years of Solar-System history. CAIs, the first solids to condense in the Solar System, formed close to the Sun. They were, however, concentrated within the outer disk and depleted within the inner disk. Future models of the structure and evolution of the protoplanetary disk should account for this distribution pattern of CAIs.

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Compositions of carbonaceous-type asteroidal cores in the early solar system

Cited by 12 publications

References 65 publications

Disk transport rates from Ti isotopic signatures of refractory inclusions

Disk transport rates from Ti isotopic signatures of refractory inclusions

Impact‐induced devolatilization of four ungrouped ataxites and the formation of a silica glass spherule in ALHA77255

Compositions of iron-meteorite parent bodies constrain the structure of the protoplanetary disk

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