The origin of refractory minerals in comet 81P/Wild 2

Chi, Miaofang; Ishii, H. A.; Simon, S. B.; Bradley, J. P.; Dai, Z. R.; Joswiak, D. J.; Browning, Nigel D.; Matrajt, G.

doi:10.1016/j.gca.2009.08.033

Cited by 35 publications

(21 citation statements)

References 28 publications

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“…The spectrum of the Inti pyroxene is remarkably similar to that of the Allende reference material. Thus, the EELS results (Chi 2008;Chi et al, Forthcoming) show that Inti Ti-rich pyroxene has a significant Ti 3+ component, probably well within the range of fassaite from Allende. The presence of Ti 3+ in Inti tpx is also indicated by low cation totals (per six oxygen anions), with all Ti reported as Ti 4+ , as in the analyses shown in Table 3.…”

Section: Clinopyroxenementioning

confidence: 89%

A refractory inclusion returned by Stardust from comet 81P/Wild 2

Simon

Joswiak

Ishii

et al. 2008

Meteorit & Planetary Scien

115

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Abstract-Among the samples returned from comet 81P/Wild 2 by the Stardust spacecraft is a suite of particles from one impact track (Track 25) that are Ca-, Al-rich and FeO-free. We studied three particles from this track that range in size from 5.3 × 3.2 µm to 15 × 10 µm. Scanning and transmission electron microscopy show that they consist of very fine-grained (typically from ~0.5 to ~2 µm) Al-rich, Ti-bearing and Ti-free clinopyroxene, Mg-Al spinel and anorthite, with trace amounts of fine perovskite, FeNi metal and osbornite (TiN) grains. In addition to these phases, the terminal particle, named "Inti", also contains melilite. All of these phases, with the exception of osbornite, are common in refractory inclusions and are predicted to condense at high temperature from a gas of solar composition. Osbornite, though very rare, has also been found in meteoritic refractory inclusions, and could have formed in a region of the nebula where carbon became enriched relative to oxygen compared to solar composition. Compositions of Ti-pyroxene in Inti are similar, but not identical, to those of fassaite from Allende inclusions. Electron energy loss spectroscopy shows that Ti-rich pyroxene in Inti has Ti 3+ /Ti 4+ within the range of typical meteoritic fassaite, consistent with formation under reducing conditions comparable to those of a system of solar composition. Inti is 16 O-rich, with δ 18 O≈δ 17 O≈-40‰, like unaltered phases in refractory inclusions and refractory IDPs. With grain sizes, mineralogy, mineral chemistry, and an oxygen isotopic composition like those of refractory inclusions, we conclude that Inti is a refractory inclusion that formed in the inner solar nebula. Identification of a particle that formed in the inner solar system among the comet samples demonstrates that there was transport of materials from the inner to the outer nebula, probably either in a bipolar outflow or by turbulence.

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Section: Clinopyroxenementioning

confidence: 89%

A refractory inclusion returned by Stardust from comet 81P/Wild 2

Simon

Joswiak

Ishii

et al. 2008

Meteorit & Planetary Scien

115

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“…These minerals can form only at temperatures on the order of thousands of kelvins, but they are found in comets (Campins & Ryan 1989;Wooden et al 2005;Chi et al 2009;Kelley & Wooden 2009). How the high temperature minerals got to the cold region where comets form is a classic problem.…”

Section: Implications For Cometsmentioning

confidence: 99%

Nebular dead zone effects on the D/H ratio in chondrites and comets

Ali-Dib

Martin

Petit

et al. 2015

A&A

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Context. Comets and chondrites show non-monotonic behavior of their deuterium-to-hydrogen (D/H) ratio as a function of their formation location from the Sun. This is difficult to explain with a classical protoplanetary disk model that has a decreasing temperature structure with radius from the Sun. Aims. We want to understand if a protoplanetary disc with a dead zone, i.e., a region of zero or low turbulence, can explain the measured D/H values in comets and chondrites. Methods. We use time snapshots of a vertically layered disk model with turbulent surface layers and a dead zone at the midplane. The disc has a non-monotonic temperature structure due to increased heating from self-gravity in the outer parts of the dead zone. We couple this to a D/H ratio evolution model in order to quantify the effect of such thermal profiles on D/H enrichment in the nebula. Results. We find that the local temperature peak in the disk can explain the diversity in the D/H ratios of different chondritic families. This disk temperature profile leads to a non-monotonic D/H enrichment evolution, allowing these families to acquire their different D/H values while forming in close proximity. The formation order we infer for these families is compatible with that inferred from their water abundances. However, we find that even for very young disks, the thermal profile reversal is too close to the Sun to be relevant for comets.

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“…Terminal particles correspond to the best-studied Stardust material until now. They are made of coarse grains, including CAI-like or chondrule-like assemblages Leroux et al, 2008a;Nakamura et al, 2008;Simon et al, 2008;Chi et al, 2009;Jacob et al, 2009a). With SXRF data taken from seven Stardust tracks, Lanzirotti et al (2008) showed that the quantity of material (based on the iron mass) contained within the terminal particles is variable, from 10% to 80% depending on the track morphology.…”

Section: Introductionmentioning

confidence: 99%