Type C Ca, Al-rich inclusions from Allende: Evidence for multistage formation

Krot, Alexander N.; Yurimoto, H.; Hutcheon, I. D.; Libourel, G.; Chaussidon, M.; Tissandier, L.; Petaev, M. I.; MacPherson, G. J.; Paque, J. M.; Wark, D. A.

doi:10.1016/j.gca.2007.03.040

Cited by 48 publications

(49 citation statements)

References 41 publications

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“…Matzel et al (2010) 16 O-poor gas that was not present during CAI formation but common during chondrule formation (Krot et al 2007a). This in combination with Type B and C mineralogy led Krot et al (2007b) Mg systematics was reset ≥2.6 Myr after CAI. These measurements show that these particles were formed or processed in the inner solar system 1.7-3 Myr after CAI, and later were transported to the comet forming region.…”

Section: Radiometric Dating Of Comet Materialsmentioning

confidence: 88%

The primordial nucleus of comet 67P/Churyumov-Gerasimenko

Davidsson

Sierks

Güttler

et al. 2016

A&A

187

162

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Context. We investigate the formation and evolution of comet nuclei and other trans-Neptunian objects (TNOs) in the solar nebula and primordial disk prior to the giant planet orbit instability foreseen by the Nice model. Aims. Our goal is to determine whether most observed comet nuclei are primordial rubble-pile survivors that formed in the solar nebula and young primordial disk or collisional rubble piles formed later in the aftermath of catastrophic disruptions of larger parent bodies. We also propose a concurrent comet and TNO formation scenario that is consistent with observations. Methods. We used observations of comet 67P/Churyumov-Gerasimenko by the ESA Rosetta spacecraft, particularly by the OSIRIS camera system, combined with data from the NASA Stardust sample-return mission to comet 81P/Wild 2 and from meteoritics; we also used existing observations from ground or from spacecraft of irregular satellites of the giant planets, Centaurs, and TNOs. We performed modeling of thermophysics, hydrostatics, orbit evolution, and collision physics. Results. We find that thermal processing due to short-lived radionuclides, combined with collisional processing during accretion in the primordial disk, creates a population of medium-sized bodies that are comparably dense, compacted, strong, heavily depleted in supervolatiles like CO and CO 2 ; they contain little to no amorphous water ice, and have experienced extensive metasomatism and aqueous alteration due to liquid water. Irregular satellites Phoebe and Himalia are potential representatives of this population. Collisional rubble piles inherit these properties from their parents. Contrarily, comet nuclei have low density, high porosity, weak strength, are rich in supervolatiles, may contain amorphous water ice, and do not display convincing evidence of in situ metasomatism or aqueous alteration. We outline a comet formation scenario that starts in the solar nebula and ends in the primordial disk, that reproduces these observed properties, and additionally explains the presence of extensive layering on 67P/Churyumov-Gerasimenko (and on 9P/Tempel 1 observed by Deep Impact), its bi-lobed shape, the extremely slow growth of comet nuclei as evidenced by recent radiometric dating, and the low collision probability that allows primordial nuclei to survive the age of the solar system. Conclusions. We conclude that observed comet nuclei are primordial rubble piles, and not collisional rubble piles. We argue that TNOs formed as a result of streaming instabilities at sizes below ∼400 km and that ∼350 of these grew slowly in a low-mass primordial disk to the size of Triton, Pluto, and Eris, causing little viscous stirring during growth. We thus propose a dynamically cold primordial disk, which prevented mediumsized TNOs from breaking into collisional rubble piles and allowed the survival of primordial rubble-pile comets. We argue that comets formed by hierarchical agglomeration out of material that remained after TNO formation, and that this slow growth was a necessity...

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Section: Radiometric Dating Of Comet Materialsmentioning

confidence: 88%

The primordial nucleus of comet 67P/Churyumov-Gerasimenko

Davidsson

Sierks

Güttler

et al. 2016

A&A

187

162

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“…ACCEPTED MANUSCRIPT Thermodynamic analysis suggests that, under equilibrium conditions for melilite of Åk (covering nearly the entire range of melilite compositions in CAI 160), these reactions occur at T<750°C (Hutcheon and Newton, 1981;Krot et al, 2007b). However, the common presence of unaltered melilite-anorthite intergrowths in the Allende Type C CAIs 100, 160 and 6-1-72 indicates lack of equilibrium.…”

Section: Postcrystallization Oxygen Isotopic Exchange In the Allende mentioning

confidence: 99%

“…The setting for this exchange is highly debated, and both nebular (e.g., Hutcheon and Newton, 1981;Kimura and Ikeda, 1998;MacPherson, 2003;Fagan et al, 2005Fagan et al, , 2006Fagan et al, , 2007bUshikubo et al, 2006) and asteroidal (Krot et al, 2007b) heating have been proposed to explain formation of grossular in CV chondrites. Both models have problems.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

“…13. Oxygen isotopic compositions of Type C CAIs ABC (a, b) and TS26 (c, d) with chondrule fragments in their peripheries (from Krot et al, 2007b). In "a" and "c", data are plotted as δ 17 O vs. δ 18 O; in "b" and "d", the same data, grouped by minerals, are plotted as ∆ 17 O. an = anorthite; aug = augite; Cr-sp = Cr-spinel; di = Al,Ti-diopside; lpx = low-Ca pyroxene; mel = melilite; ol = olivine; sp = spinel.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

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Oxygen isotopic compositions of Allende Type C CAIs: Evidence for isotopic exchange during nebular melting and asteroidal metamorphism

Krot

Chaussidon

Yurimoto

et al. 2008

Geochimica et Cosmochimica Acta

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“…• C (Huss et al 2006;Krot et al 2007), whereas that of types 1 and 2 carbonaceous chondrites might be around 100…”

Section: Isotopic Diffusion In Thermally Evolving Planetesimalsmentioning

confidence: 99%

Diffusion of Oxygen Isotopes in Thermally Evolving Planetesimals and Size Ranges of Presolar Silicate Grains

Wakita

Nozawa

Hasegawa

2017

ApJ

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Presolar grains are small particles found in meteorites through their isotopic compositions which are considerably different from those of materials in the Solar System. If some isotopes in presolar grains diffused out beyond their grain sizes when they were embedded in parent bodies of meteorites, their isotopic compositions could be washed out, and hence the grains cannot be identified as presolar grains any more. We explore this possibility for the first time by self-consistently simulating the thermal evolution of planetesimals and the diffusion length of 18 O in presolar silicate grains. Our results show that presolar silicate grains smaller than ∼ 0.03µm cannot keep their original isotopic compositions even if the host planetesimals experienced maximum temperature as low as 600• C. Since this temperature corresponds to the one experienced by petrologic type 3 chondrites, the isotopic diffusion can constrain the size of presolar silicate grains discovered in such chondrites to be larger than ∼ 0.03µm. We also find that the diffusion lengths of 18 O reach ∼ 0.3 − 2µm in planetesimals that were heated up to 700-800• C. This indicates that, if the original size of presolar grains spans a range from ∼ 0.001µm to ∼ 0.3µm like that in the interstellar medium, the isotopic records of the presolar grains may be almost completely lost in such highly thermalized parent bodies. We propose that isotopic diffusion could be a key process to control the size distribution and abundance of presolar grains in some types of chondrites.

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Type C Ca, Al-rich inclusions from Allende: Evidence for multistage formation

Cited by 48 publications

References 41 publications

The primordial nucleus of comet 67P/Churyumov-Gerasimenko

The primordial nucleus of comet 67P/Churyumov-Gerasimenko

Oxygen isotopic compositions of Allende Type C CAIs: Evidence for isotopic exchange during nebular melting and asteroidal metamorphism

Diffusion of Oxygen Isotopes in Thermally Evolving Planetesimals and Size Ranges of Presolar Silicate Grains

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