Pure iron grains are rare in the universe

Kimura, Yuki; Tanaka, Kyoko; Nozawa, Takaya; Takeuchi, Shinsuke; Inatomi, Yuko

doi:10.1126/sciadv.1601992

Cited by 32 publications

(26 citation statements)

References 34 publications

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“…Rapid whisker growth as opposed to the formation of a protective iron shell implies that sulfides are easily destroyed under such conditions. Metallic iron is predicted to appear as a byproduct of this alteration process in the ISM and might exists there even though its primary formation by homogeneous nucleation from supernova ejecta appears to be highly ineffective 63 . Metallic iron in the ISM can be an important catalysts for molecule formation 64 and can produce magnetic dipole emissions that disturb the cosmic microwave background 65 .…”

Section: Discussionmentioning

confidence: 99%

Iron whiskers on asteroid Itokawa indicate sulfide destruction by space weathering

et al. 2020

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Extraterrestrial iron sulfide is a major mineral reservoir of the cosmochemically and astrobiologically important elements iron and sulfur. Sulfur depletion on asteroids is a longstanding, yet unresolved phenomenon that is of fundamental importance for asteroid evolution and sulfur delivery to the Earth. Understanding the chemistry of such environments requires insight into the behavior of iron sulfides exposed to space. Here we show that troilite (FeS) grains recovered from the regolith of asteroid 25143 Itokawa have lost sulfur during long-term space exposure. We report the widespread occurrence of metallic iron whiskers as a decomposition product formed through irradiation of the sulfide by energetic ions of the solar wind. Whisker growth by ion irradiation is a novel and unexpected aspect of space weathering. It implies that sulfur loss occurs rapidly and, furthermore, that ion irradiation plays an important role in the redistribution of sulfur between solids and gas of the interstellar medium.

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Section: Discussionmentioning

confidence: 99%

Iron whiskers on asteroid Itokawa indicate sulfide destruction by space weathering

et al. 2020

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“…The nature of the chemical binding of iron to interstellar dust particles is currently being debated. For example, from experiments in microgravity, Kimura et al (2017) concluded that the probability of the formation of pure iron grains should be very low and that, consequently, iron should be bound in iron compounds or accreted as impurities on other grains in the ISM. Another hypothesis was pursued by Bilalbegović et al (2016) who calculated infrared absorption spectra of hydrogenated iron particles.…”

Section: Comparison With Other Forms Of Ironmentioning

confidence: 99%

Near L-edge Single and Multiple Photoionization of Doubly Charged Iron Ions

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Martins

Beerwerth³

et al. 2021

ApJ

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Using the photon-ion merged-beams technique at a synchrotron light source, we have measured relative cross sections for single and up to five-fold photoionization of Fe 2+ ions in the energy range of 690-920eV. This range contains thresholds and resonances associated with ionization and excitation of 2p and 2s electrons. Calculations were performed to simulate the total absorption spectra. The theoretical results show very good agreement with the experimental data, if overall energy shifts of up to 2.5eV are applied to the calculated resonance positions and assumptions are made about the initial experimental population of the various levels of the Fe 2+ ([Ar]3d 6 ) ground configuration. Furthermore, we performed extensive calculations of the Auger cascades that result when an electron is removed from the 2p subshell of Fe 2+ . These computations lead to a better agreement with the measured product-charge-state distributions as compared to earlier work. We conclude that the L-shell absorption features of low-charged iron ions are useful for identifying gas-phase iron in the interstellar medium and for discriminating against the various forms of condensed-phase iron bound to composite interstellar dust grains.Unified Astronomy Thesaurus concepts: Interstellar atomic gas (833); Interstellar clouds (834); Interstellar medium (847); Interstellar absorption (831); Line intensities (2084); Atomic spectroscopy (2099); Line positions (2085); X-ray astronomy (1810); Laboratory astrophysics (2004)

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“…At a gas pressure of 4.0 × 10 4 Pa, the temperature of the nanoparticles is almost identical to that of the surrounding gas 19 . Owing to the reported temperature field around the evaporation source at 2226 ± 22 K under an Ar atmosphere of 4.0 × 10 4 Pa 20 , the nascent nucleated nanoparticles can retain a temperature of about 1000 K for a few seconds. This relatively long incubation time for the nucleation can induce the formation of α-Al 2 O 3 within the liquid-like particles under microgravity conditions.…”

Section: Discussionmentioning

confidence: 99%

“…Consequently, the Al 2 O 3 nuclei have higher possibility to overcome a large barrier to form the most stable corundum phase. In addition, the slower cooling permits the gaseous atoms to collide more frequently and, on a longer timescale of gas cooling, provides a more realistic simulation of the grain formation in gas outflows from AGB stars 20 . Based on this concept, we performed an ideal-nucleation experiment in a microgravitational environment of 2.2 × 10 −3 m s −2 (2.2 × 10 −4 G) aboard the sounding rocket S-520 30 and successfully reproduce a 13 μm band with a very narrow width of 0.5–0.6 μm.…”

Section: Introductionmentioning

confidence: 99%

Sounding-rocket microgravity experiments on alumina dust

et al. 2018

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Alumina (Al2O3) is believed to be the first major condensate to form in the gas outflow from oxygen-rich evolved stars because of the refractoriness and that α-Al2O3 (corundum, most stable polymorph) is a potential origin of a 13 μm feature that appears close to stars. However, no one has directly reproduced the 13 μm feature experimentally, and it has remained as a noteworthy unidentified infrared band. Here, we report nucleation experiments on Al2O3 nanoparticles monitored by a specially designed infrared spectrometer in the microgravity environment of a sounding rocket. The conditions approximate to those around asymptotic giant branch (AGB) stars. The measured spectra of the nucleated Al2O3 show a sharp feature at a wavelength of 13.55 μm and comparable in width to that observed near oxygen-rich AGB stars. Our finding that α-Al2O3 nucleates under certain condition provides a solid basis to elaborate condensation models of dust around oxygen-rich evolved stars.

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Pure iron grains are rare in the universe

Abstract: The extremely low sticking probability of iron inhibits the formation of metallic iron grains around evolved stars.

Cited by 32 publications

References 34 publications

Iron whiskers on asteroid Itokawa indicate sulfide destruction by space weathering

Iron whiskers on asteroid Itokawa indicate sulfide destruction by space weathering

Near L-edge Single and Multiple Photoionization of Doubly Charged Iron Ions

Sounding-rocket microgravity experiments on alumina dust

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