Re-evaluation of the chemistry of dust grains in the coma of comet Halley

Mukhin, L. M.; Dolnikov, Gennady; Evlanov, E. N.; Fomenkova, M. N.; Prilutsky, O. F.; Sagdeev, R. Z.

doi:10.1038/350480a0

Cited by 17 publications

(7 citation statements)

References 7 publications

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“…The smallest grains in the comet Halley coma can be subdivided into “heavy particles” (>10 −13 g) and “light particles” (<5 × 10 −16 g) with slightly different compositions whereby the “light particles” contained more grains with very low Fe/(Fe + Mg) ratios than the “heavy” particles (Mukhin et al. ). The “light particle” compositions resembled the Mg,Fe‐rich particles reported by Jessberger et al.…”

Section: Discussionmentioning

confidence: 99%

“…A considerable number of “light particles” contained Mg, but without Si, that could be MgO, Mg(OH) 2 , or MgCO 3 (Mukhin et al. ; Fomenkova et al. ).…”

Section: Discussionmentioning

confidence: 99%

“…4a) that did not match a CI average composition and (2) the same data, but adjusted, assuming that this dust from the comet had a CI average composition. The smallest grains in the comet Halley coma can be subdivided into "heavy particles" (>10 À13 g) and "light particles" (<5 9 10 À16 g) with slightly different compositions whereby the "light particles" contained more grains with very low Fe/(Fe + Mg) ratios than the "heavy" particles (Mukhin et al 1991). The "light particle" compositions resembled the Mg,Fe-rich particles reported by Jessberger et al (1988).…”

Section: Comet P/halleymentioning

confidence: 99%

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The formation of Mg,Fe‐silicates by reactions between amorphous magnesiosilica smoke particles and metallic iron nanograins with implications for comet silicate origins

Rietmeijer

Nuth

Pun

2013

Meteorit & Planetary Scien

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Abstract-This thermal annealing experiment at 1000 K for up to 167 h used a physical mixture of vapor phase-condensed magnesiosilica grains and metallic iron nanograins to test the hypothesis that a mixture of magnesiosilica grains and an Fe-source would lead to the formation of ferromagnesiosilica grains. This exploratory study found that coagulation and thermal annealing of amorphous magnesiosilica and metallic grains yielded ferromagnesiosilica grains with the Fe/(Fe + Mg) ratios in interplanetary dust particles. Furthermore, decomposition of brucite present in the condensed magnesiosilica grains was the source for water and the cause of different iron oxidation states, and the formation of amorphous Fe 3+ -ferrosilica, amorphous Fe 3+ -Mg, Fe-silicates, and magnesioferrite during thermal annealing. Fayalite and ferrosilite that formed from silica/FeO melts reacted with forsterite and enstatite to form Mg, Fe-silicates. The presence of iron in different oxidation states in extraterrestrial materials almost certainly requires active asteroid-like parent bodies. If so, the possible presence of trivalent Fe compounds in comet P/Halley suggests that Halley-type comets are a mixture of preserved presolar and processed solar nebula dust. The results from this thermal annealing experiment further suggest that the Fe-silicates detected in the impact-induced ejecta from comet 9P/Temple 1 might be of secondary origin and related to the impact experiment or to processing in a regolith.

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Section: Discussionmentioning

confidence: 99%

“…A considerable number of “light particles” contained Mg, but without Si, that could be MgO, Mg(OH) 2 , or MgCO 3 (Mukhin et al. ; Fomenkova et al. ).…”

Section: Discussionmentioning

confidence: 99%

Section: Comet P/halleymentioning

confidence: 99%

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The formation of Mg,Fe‐silicates by reactions between amorphous magnesiosilica smoke particles and metallic iron nanograins with implications for comet silicate origins

Rietmeijer

Nuth

Pun

2013

Meteorit & Planetary Scien

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“…The smallest grains were subdivided into “heavy particles” (>10 −13 g) and “light particles” (<5 × 10 −16 g), whereby the “light particles” group had more grains with very low Fe/(Fe+Mg) ratios than the “heavy” particles (Mukhin et al. ). Thermal annealing experiments showed that such ferromagnesiosilica nanograins are already chemically evolved silicates (Rietmeijer and Nuth ).…”

Section: Introductionmentioning

confidence: 99%

“…The measured dust was dominated by Mg-Fe-Si grains with Fe/(Fe+Mg) compositions ranging from zero to one but with no distinct groupings, plus a few FeS-dominated grains (Jessberger et al 1988;Fomenkova et al 1992). The smallest grains were subdivided into "heavy particles" (>10 À13 g) and "light particles" (<5 9 10 À16 g), whereby the "light particles" group had more grains with very low Fe/ (Fe+Mg) ratios than the "heavy" particles (Mukhin et al 1991). Thermal annealing experiments showed that such ferromagnesiosilica nanograins are already chemically evolved silicates .…”

Section: Introductionmentioning

confidence: 99%

The smallest comet 81P/Wild 2 dust dances around the CI composition

Rietmeijer

2015

Meteorit & Planetary Scien

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The bulbous Stardust track #80 (C2092,3,80,0,0) is a huge cavity. Allocations C2092,2,80,46,1 nearest the entry hole and C2092,2,80,47,6 about 0.8 mm beneath the entry hole provide evidence of highly chaotic conditions during capture. They are dominated by nonvesicular low‐Mg silica glass instead of highly vesicular glass found deeper into this track which is consistent with the escape of magnesiosilica vapors generated from the smallest comet grains. The survival of delicate (Mg,Al,Ca)‐bearing silica glass structures is unique to the entry hole. Both allocations show a dearth of surviving comet dust except for a small enstatite, a low‐Ca hypersthene grain, and a Ti‐oxide fragment. Finding scattered TiO2 fragments in the silica glass could support, but not prove, TiO2 grain fragmentation during hypervelocity capture. The here reported dearth in mineral species is in marked contrast to the wealth of surviving silicate and oxide minerals deeper into the bulb. Both allocations show Fe‐Ni‐S nanograins dispersed throughout the low‐Mg silica glass matrix. It is noted that neither comet Halley nor Wild 2 had a CI bulk composition for the smallest grains. Using the analogs of interplanetary dust particles (IDPs) and cluster IDPs it is argued that a CI chondritic composition requires the mixing of nonchondritic components in the appropriate proportions. So far, the fine‐grained Wild 2 dust is biased toward nonchondritic ferromagnesiosilica materials and lacking contributions of nonchondritic components with Mg‐Fe‐Ni‐S[Si‐O] compositions. To be specific, “Where are the GEMS”? The GEMS look‐alike found in this study suggests that evidence of GEMS in comet Wild 2 may still be found in the Stardust glass.

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