Mineralogy and petrology of Stardust particles encased in the bulb of track 80: TEM investigation of the Wild 2 fine-grained material

Stodolna, Julien; Jacob, Damien; Leroux, Hugues

doi:10.1016/j.gca.2012.03.026

Cited by 39 publications

(59 citation statements)

References 75 publications

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“…; Stodolna et al. ). Altogether, these results show that a significant number of impacting cometary particles were made of poorly cohesive assemblage, which broke up during the hypervelocity impact into the aerogel.…”

Section: Discussionmentioning

confidence: 97%

Fine‐grained material encased in microtracks of Stardust samples

Leroux

Jacob

2013

Meteorit & Planetary Scien

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Abstract-Dust from comet 81P/Wild 2 was captured at high speed in silica aerogel collectors during the Stardust mission. Studies of deceleration tracks in aerogel showed that a number of cometary particles were poorly cohesive and fragmented during impact. Fragments are now scattered along the walls of impact cavities. Here, we report a transmission electron microscope study of a piece of aerogel extracted from the wall of track 10. We focused on micron-sized secondary tracks along which fragments of a finegrained material are disseminated. Two populations of fragments were identified. The first is made of polycrystalline silicate assemblages (olivine, pyroxene, and spinel) that appear to be chemically related to each other. The second corresponds to silica-rich glassy clumps characteristic of a mixture of melted cometary material and aerogel. A significant number of fragments have been found with a composition close to chondritic CI for the major elements Fe-Mg-S at a submicron scale. These fragments have thus never been chemically differentiated by high-temperature processes prior to the accretion on the comet, in contrast to terminal particles, which are dominated by larger, denser, and frequently monomineralic components.

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Section: Discussionmentioning

confidence: 97%

Fine‐grained material encased in microtracks of Stardust samples

Leroux

Jacob

2013

Meteorit & Planetary Scien

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“…Comets, however, appear to be different. The Stardust samples have been searched for phyllosilicates, yet none has been found (Stodolna et al 2010(Stodolna et al , 2012Berger et al 2011;Brownlee et al 2012;Joswiak et al 2012). Laboratory experiments of the capture process indicate that phyllosilicates have a substantial chance of survival (Noguchi et al 2007;Foster et al 2008;Wozniakiewicz et al 2010), suggesting these minerals should have been found if they are common ).…”

Section: Aqueous Alteration In the Outer Solar Systemmentioning

confidence: 99%

“…The observationally established presence of silica at a 2-10% level in protostellar disks combined with their presence in 81P but absence in ordinary and carbonaceous chondrites (where liquid water quickly destroys silica) suggest that 81P was not a host of in situ aqueous alteration. Yet, the Stardust samples contain examples of grains made of magnetite (Stodolna et al 2010(Stodolna et al , 2012, carbonate (Flynn et al 2009), cubanite (CuFe 2 S 3 ), sphalerite ((Fe, Zn)S), and Ni-bearing pyrrhotite (Berger et al 2011). These minerals are known to form during aqueous alteration, although magnetite, Zn, Ni-bearing sulfides, and carbonates may form in other ways (Flynn et al 2009;Joswiak et al 2012).…”

Section: Aqueous Alteration In the Outer Solar Systemmentioning

confidence: 99%

The primordial nucleus of comet 67P/Churyumov-Gerasimenko

Davidsson

Sierks

Güttler

et al. 2016

A&A

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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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“…Unfortunately, the captured fine material becomes intimately mixed with melted aerogel along the track walls, which greatly complicates its analysis and interpretation. Efforts are underway to compress and concentrate surviving fine grains from bulbous tracks, but initial results suggest that many grains melted on impact (Stodolna et al ; Brownlee et al. ).…”

Section: Introductionmentioning

confidence: 99%

Survival of refractory presolar grain analogs during Stardust‐like impact into Al foils: Implications for Wild 2 presolar grain abundances and study of the cometary fine fraction

Croat

Floss

Haas

et al. 2015

Meteorit & Planetary Scien

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We present results of FIB–TEM studies of 12 Stardust analog Al foil craters which were created by firing refractory Si and Ti carbide and nitride grains into Al foils at 6.05 km s−1 with a light‐gas gun to simulate capture of cometary grains by the Stardust mission. These foils were prepared primarily to understand the low presolar grain abundances (both SiC and silicates) measured by SIMS in Stardust Al foil samples. Our results demonstrate the intact survival of submicron SiC, TiC, TiN, and less‐refractory Si3N4 grains. In small (<2 μm) craters that are formed by single grain impacts, the entire impacting crystalline grain is often preserved intact with minimal modification. While they also survive in crystalline form, grains at the bottom of larger craters (>5 μm) are typically fragmented and are somewhat flattened in the direction of impact due to partial melting and/or plastic deformation. The low presolar grain abundance estimates derived from SIMS measurements of large craters (mostly >50 μm) likely result from greater modification of these impactors (i.e., melting and isotopic dilution), due to higher peak temperatures/pressures in these crater impacts. The better survivability of grains in smaller craters suggests that more accurate presolar grain estimates may be achievable through measurement of such craters. It also suggests small craters can provide a complementary method of study of the Wild 2 fine fraction, especially for refractory CAI‐like minerals.

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Mineralogy and petrology of Stardust particles encased in the bulb of track 80: TEM investigation of the Wild 2 fine-grained material

Cited by 39 publications

References 75 publications

Fine‐grained material encased in microtracks of Stardust samples

Fine‐grained material encased in microtracks of Stardust samples

The primordial nucleus of comet 67P/Churyumov-Gerasimenko

Survival of refractory presolar grain analogs during Stardust‐like impact into Al foils: Implications for Wild 2 presolar grain abundances and study of the cometary fine fraction

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