Magnetite in Comet Wild 2: Evidence for parent body aqueous alteration

Hicks, L. J.; MacArthur, J. L.; Bridges, J. C.; Price, M. C.; Wickham-Eade, J. E.; Burchell, M. J.; Hansford, G. M.; Butterworth, A. L.; Gurman, S. J.; Baker, S. H.

doi:10.1111/maps.12909

Cited by 45 publications

(17 citation statements)

References 95 publications

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“…Hints for traces of aqueous alteration were found in comet Wild 2 minerals (e.g. Berger et al 2011;Mikouchi et al 2007;Hicks et al 2017;Hanner and Zolensky 2010). Spitzer spectra of 9P/Tempel 1 acquired during the Deep Impact mission could contain a contribution from a few percent of hydrated silicates, although this is debated (Lisse et al 2006).…”

Section: On the Refractory (Dust) Phase Of 67p/c-g And Other Cometsmentioning

confidence: 99%

On the Origin and Evolution of the Material in 67P/Churyumov-Gerasimenko

et al. 2020

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Primitive objects like comets hold important information on the material that formed our solar system. Several comets have been visited by spacecraft and many more have been observed through Earth-and space-based telescopes. Still our understanding remains limited. Molecular abundances in comets have been shown to be similar to interstellar ices and thus indicate that common processes and conditions were involved in their formation. The samples returned by the Stardust mission to comet Wild 2 showed that the bulk refractory material was processed by high temperatures in the vicinity of the early sun. The recent Rosetta mission acquired a wealth of new data on the composition of comet 67P/Churyumov-Gerasimenko (hereafter 67P/C-G) and complemented earlier observations of other comets. The isotopic, elemental, and molecular abundances of the volatile, semivolatile, and refractory phases brought many new insights into the origin and processing of the incorporated material. The emerging picture after Rosetta is that at least part of the volatile material was formed before the solar system and that cometary nuclei agglomerated over a wide range of heliocentric distances, different from where they are found today. Deviations from bulk solar system abundances indicate that the material was not fully homogenized at the location of comet formation, despite the radial mixing implied by the Stardust results. Post-formation evolution of the material might play an important role, which further

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Section: On the Refractory (Dust) Phase Of 67p/c-g And Other Cometsmentioning

confidence: 99%

On the Origin and Evolution of the Material in 67P/Churyumov-Gerasimenko

et al. 2020

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“…; Bridges et al. ; Hicks et al ). One terminal particle from track 183 was found to consist mainly of Cr‐rich magnetite nanoparticles (De Gregorio personal communication).…”

Section: Objective 5: Search For Signs Of Exposure To Liquid Watermentioning

confidence: 99%

“…Two magnetite terminal particles in Stardust track 187, identified by XRD at the Diamond synchrotron (Bridges et al. ; Hicks et al ).…”

Section: Objective 5: Search For Signs Of Exposure To Liquid Watermentioning

confidence: 99%

The future of Stardust science

Westphal

Bridges

Brownlee

et al. 2017

Meteorit & Planetary Scien

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Recent observations indicate that >99% of the small bodies in the solar system reside in its outer reaches-in the Kuiper Belt and Oort Cloud. Kuiper Belt bodies are probably the best-preserved representatives of the icy planetesimals that dominated the bulk of the solid mass in the early solar system. They likely contain preserved materials inherited from the protosolar cloud, held in cryogenic storage since the formation of the solar system. Despite their importance, they are relatively underrepresented in our extraterrestrial sample collections by many orders of magnitude (~10 13 by mass) as compared with the asteroids, represented by meteorites, which are composed of materials that have generally been strongly altered by thermal and aqueous processes. We have only begun to scratch the surface in understanding Kuiper Belt objects, but it is already clear that the very limited samples of them that we have in our laboratories hold the promise of dramatically expanding our understanding of the formation of the solar system. Stardust returned the first samples from a known small solar system body, the Jupiter-family comet 81P/Wild 2, and, in a separate collector, the first solid samples from the local interstellar medium. The first decade of Stardust research resulted in more than 142 peer-reviewed publications, including 15 papers in Science. Analyses of these amazing samples continue to yield unexpected discoveries and to raise new questions about the history of the early solar system. We identify nine high-priority scientific objectives for future Stardust analyses that address important unsolved problems in planetary science. 1862A. J. Westphal et al.

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“…Magnetite and hematite associated with Fe-metal were observed in Stardust tracks 41 and 121, and were interpreted as alteration products, either through the aqueous alteration of metal on comet Wild 2 or oxidation of metal during capture heating in the silica aerogel collector (Bridges et al 2010). Magnetite was also observed with pyrrhotite in the terminal particle of track 134 (Changela et al 2012), in terminal particles from tracks 178 and 187 (Hicks et al 2017). Isolated, μm sized grains of magnetite have been reported in the walls of Track 80, also interpreted to result from aqueous alteration on the comet (Stodolna et al 2012).…”

Section: Magnetite and Chromite In The Stardust Collectionmentioning

confidence: 98%

Evidence for Reduced, Carbon-rich Regions in the Solar Nebula from an Unusual Cometary Dust Particle

Gregorio

Stroud

Nittler

et al. 2017

ApJ

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Geochemical indicators in meteorites imply that most formed under relatively oxidizing conditions. However, some planetary materials, such as the enstatite chondrites, aubrite achondrites, and Mercury, were produced in reduced nebular environments. Because of large-scale radial nebular mixing, comets and other Kuiper Belt objects likely contain some primitive material related to these reduced planetary bodies. Here, we describe an unusual assemblage in a dust particle from comet 81P/Wild 2 captured in silica aerogel by the NASA Stardust spacecraft. The bulk of this ∼20 μm particle is comprised of an aggregate of nanoparticulate Cr-rich magnetite, containing opaque sub-domains composed of poorly graphitized carbon (PGC). The PGC forms conformal shells around tiny 5-15 nm core grains of Fe carbide. The C, N, and O isotopic compositions of these components are identical within errors to terrestrial standards, indicating a formation inside the solar system. Magnetite compositions are consistent with oxidation of reduced metal, similar to that seen in enstatite chondrites. Similarly, the core-shell structure of the carbide + PGC inclusions suggests a formation via FTT reactions on the surface of metal or carbide grains in warm, reduced regions of the solar nebula. Together, the nanoscale assemblage in the cometary particle is most consistent with the alteration of primary solids condensed from a C-rich, reduced nebular gas. The nanoparticulate components in the cometary particle provide the first direct evidence from comets of reduced, carbon-rich regions that were present in the solar nebula.

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Magnetite in Comet Wild 2: Evidence for parent body aqueous alteration

Cited by 45 publications

References 95 publications

On the Origin and Evolution of the Material in 67P/Churyumov-Gerasimenko

On the Origin and Evolution of the Material in 67P/Churyumov-Gerasimenko

The future of Stardust science

Evidence for Reduced, Carbon-rich Regions in the Solar Nebula from an Unusual Cometary Dust Particle

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