Impacts on the CV parent body: A coordinated, multiscale fabric analysis of the Allende meteorite

1,2L. V. Forman,2,3,4L. Daly,1P. A. Bland,1,2,5G. K. Benedix,6C. Corrigan
Meteoritics & Planetary Science (in Press) Open Access Link to Article []
1Space Science & Technology Centre, School of Earth & Planetary Sciences, Curtin University, Bentley, Western Australia, Australia
2Department of Earth & Planetary Sciences, Western Australian Museum, Perth, Western Australia, Australia
3School of Geographical & Earth Sciences, University of Glasgow, Glasgow, UK
4Australian Centre for Microscopy and Microanalysis, University of Sydney, Sydney, New South Wales, Australia
5Planetary Science Institute, Tucson, Arizona, USA
6Department of Mineral Science, National Museum of Natural History (NMNH), Washington, DC, USA
Published by arrangement with John Wiley & Sons

Evidence of impact-induced compaction in the carbonaceous chondrites, specifically CMs and CVs, has been widely investigated utilizing microscopy techniques and impact experiments. Here, we use high-resolution photography and large area and high-resolution electron backscattered diffraction (EBSD) mapping analyses in tandem, to explore the effects of impact-induced compaction at both the meso- and micro-scales in the Allende CV3.6 carbonaceous chondrite. Macro-scale photography images of a ~25 cm slab of Allende captured meso-scale features including calcium-aluminum inclusions (CAIs) and chondrules. CAIs have a long-axis shape-preferred orientation (SPO). Examination of such meso-scale features in thin section revealed the same trend. Matrix grains from this section display a large amount of heterogeneity in petrofabric orientation; microscale, high-resolution, large area EBSD mapping of ~300,000 olivine matrix grains; high-resolution large area EBSD map across an elongate CAI; and a series of high-resolution EBSD maps around two chondrules and around the CAI revealed crystallographic preferred orientations (CPOs) in different directions. Finally, internal grains of the CAI were found to demonstrate a weak lineation CPO, the first crystallographic detection of possible CAI “flow.” All results are consistent with multiple, gentle impacts on the Allende parent body causing hemispheric compaction. The larger, more resistant components are likely to have been compressed and oriented by earlier impacts, and the matrix region petrofabrics and CAI “flow” likely occurred during subsequent impacts. Meteoritic components respond differently to impact events, and consequently, it is likely that different components would retain evidence of different impact events and angles.

Degassing of early-formed planetesimals restricted water delivery to Earth

1M. E. Newcombe,2S. G. Nielsen,1L. D. Peterson,3J. Wang,3C. M. O’D. Alexander,4A. R. Sarafian,5K. Shimizu,6,3L. R. Nittler,7A. J. Irving
Nature 615, 854-857 Link to Article [DOI]
1University of Maryland, College Park, MD, USA
2NIRVANA Laboratories, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
3Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC, USA
4Corning Incorporated, Corning, NY, USA
5University of Wisconsin, Madison, WI, USA
6School Of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA
7University of Washington, Seattle, WA, USA

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In situ oxygen, magnesium, and silicon isotopic compositions of the FUN inclusion Vigarano 1623-5

1,2Johanna Marin-Carbonne,1Kevin D. McKeegan,3,4Andrew M. Davis,5Glenn J. MacPherson,5Ruslan A. Mendybaev,5Frank M. Richter
Meteoritics & Planetary Science (in Press) Open Access Link to Article []
1Department of Earth, Planetary, and Space Sciences, University of California—Los Angeles, Los Angeles, California, USA
2Institut des Sciences de la Terre, Université de Lausanne, Lausanne, Switzerland
3Department of the Geophysical Sciences, University of Chicago, Illinois, USA
4Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA
5Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA
Published by arrangement with John Wiley & Sons

Oxygen, magnesium, and silicon isotopic abundances in Vigarano 1623-5 were studied using secondary ion mass spectrometry to investigate correlations between isotopic and petrologic properties of this unique forsterite-bearing FUN inclusion. Vigarano 1623-5 displays large, correlated mass-dependent fractionation effects, tightly linked to mineralogy within distinct petrologic units of the inclusion. The pyroxene-rich and melilite-rich interior parts of the inclusion display highly mass-fractionated isotopic compositions of oxygen, magnesium, and silicon, consistent with Rayleigh distillation during evaporation of a melt with initial oxygen composition close to a solar composition. However, the chemical composition, enriched in magnesium and silicon, suggests a precursor already fractionated by prior melt evaporation. A discontinuous igneous rim was produced by a flash-melting event followed by isotopic exchange in the rim melilite with planetary-like oxygen, mechanical fragmentation, and reassembly with an accretionary rim of heterogeneous materials. Al-rich minerals in 1623-5 show evidence for having crystallized with live 26Al but at less than the “canonical” level of most CV calcium-aluminum-rich inclusions. However, well-defined 26Al-26Mg isochrons are not found and temporal implications are ambiguous.

Shock-induced potassium and zinc isotope fractionation in ordinary chondrites and its implications

1,2,3Ying-Kui Xu,1,4Zhi Li,1,2Shi-Jie Li,3Ze-Zhou Wang,1,4De-Liang Wang,1,5Yan Fan,1,2Xiong-Yao Li,1,2Jian-Zhong Liu,6,2Dan Zhu
Geochimica et Cosmochimica Acta (in Press) Link to Article []
1Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China
2CAS Center for Excellence in Comparative Planetology, Hefei, 230022, China
3Isotope Laboratory, Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USA
4University of Chinese Academy of Sciences, Beijing, 100049, China
5Department of Geology, Northwest University, Xi’an, 710069, China
6State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China
Copyright Elsevier

To constrain how impacts influence the behavior of moderately volatile elements (MVEs), we report potassium (K) and zinc (Zn) contents and isotopic compositions of shock melt pockets (SMPs) and unmelted parts of three heavily shocked ordinary chondrites and bulk rocks of Chelyabinsk meteorite. All SMPs are enriched in K content and have lower isotopic values (δ41K = -1.99‰, -1.22‰ and -1.40‰) while the adjacent unmelted parts are enriched in heavy K isotopes (δ41K = -0.41‰, -0.01‰ and 0.04‰) compared to the bulk rocks of Chelyabinsk meteorite (δ41K = -0.77‰ and -0.73‰). By contrast, Zn is depleted in SMPs and the isotopic compositions are heavier (δ66Zn = -0.19‰, 2.42‰, 1.74‰) in SMPs than that in unmelted parts (δ66Zn = -0.65‰, 1.76‰, -0.97‰). Our results indicate a decoupling between the two MVEs that Zn is lost from shock melts while K is dramatically enriched in shock melts during impacts. The isotope fractionation of Zn is probably caused by evaporation of shock melts, while K isotope fractionation is most likely caused by solid-melt diffusion which is controlled by its incompatibility. The isotopic decoupling of K from Zn during major impacts further enhances our understanding of high temperature elemental and isotopic behavior of MVEs and may shed new light on the variously heterogeneous distribution of MVEs in solar system.

Trends in planetary science research in the Puna and Atacama Desert regions: Underrepresentation of local scientific institutions?

1A. Tavernier,2,3G. A. Pinto,4,5,6M. Valenzuela,1A. Garcia,1C. Ulloa,7R. Oses,8,9,10,11B. H. Foing
Meteoritics & Planetary Science (in Press) Link to Article []
1Instituto de Investigaciones Científicas y Tecnológicas, IDICTEC, Laboratorio de Investigacion de la Criosfera y Aguas, Universidad de Atacama, UDA, Copiapó, Chile
2Instituto de Investigación en Astronomía y Ciencias Planetarias, INCT, Universidad de Atacama, UDA, Copiapó, Chile
3Centre de Recherches Pétrographiques et Géochimiques, CRPG, Université de Lorraine, Nancy, France
4Departamento de Ciencias Geológicas, Universidad Católica del Norte, UCN, Antofagasta, Chile
5Millennium Institute of Astrophysics, MAS, Santiago, Chile
6Center for Excellence in Astrophysics and Associated Technologies, CATA, Santiago, Chile
7Centro Regional de Investigacion y Desarrollo Sustentable de Atacama, CRIDESAT, Universidad de Atacama, UDA, Copiapó, Chile
8Instituto de Investigación en Astronomía y Ciencias Planetarias, INCT, Universidad de Atacama, UDA, Copiapó, Chile
9International Lunar Exploration Working Group, ILEWG, EuroMoonMars, Noordwijk, The Netherlands
10Vrije Universiteit Amsterdam, VUA, Amsterdam, The Netherlands
11Universiteit Leiden, Leiden, The Netherlands
Published by arrangement with John Wiley & Sons

In 2019, while launching a multidisciplinary research project aimed at developing the Puna de Atacama region as a natural laboratory, investigators at the University of Atacama (Chile) conducted a bibliographic search identifying previously studied geographic points of the region and of potential interest for planetary science and astrobiology research. This preliminary work highlighted a significant absence of local institutional involvement in international publications. In light of this, a follow-up study was conducted to confirm or refute these first impressions, by comparing the search in two bibliographic databases: Web of Science and Scopus. The results show that almost 60% of the publications based directly on data from the Puna, the Altiplano, or the Atacama Desert with objectives related to planetary science or astrobiology do not include any local institutional partner (Argentina, Bolivia, Chile, and Peru). Indeed, and beyond the ethical questioning of international collaborations, Latin-American planetary science deserves a strategic structuring, networking, as well as a road map at national and continental scales, not only to enhance research, development, and innovation, but also to protect an exceptional natural heritage sampling extreme environmental niches on Earth. Examples of successful international collaborations such as the field of meteorites, terrestrial analogs, and space exploration in Chile or astrobiology in Mexico are given as illustrations and possible directions to follow to develop planetary science in South America. To promote appropriate scientific practices involving local researchers, possible responses at academic and institutional levels will eventually be discussed.

Lead-Lead (Pb-Pb) Dating of Eucrites and Mesosiderites: Implications for the Formation and Evolution of Vesta

1I. Kouvatsis,1J.A. Cartwright,2M.J. Whitehouse
Geochimica et Cosmochimica Acta (in Press) Link to Article []
1Department of Geological Sciences, University of Alabama, Tuscaloosa, AL 35487, USA
2Department of Geosciences, Swedish Museum of Natural History, SE-104 05 Stockholm, Sweden
Copyright Elsevier

Asteroid 4 Vesta is the largest known differentiated body in the asteroid belt, and is thought to be the likely parent body of howardite, eucrite, and diogenite (HED) meteorites. Howardites likely represent the vestan surface, eucrites likely crystallized as lavas in the upper crust, and diogenites likely originated from a plutonic layer deep in the crust. HEDs are potentially linked to another group of meteorites: the stony-iron mesosiderite group, due to mineralogical, geochemical, and isotopic similarities. Collision and disruption processes in the asteroid belt are key to understanding the evolution of asteroids, with impact events generating significant volumes of melt, which, if dated, can provide information on the timing and nature of such events. We performed in situ lead-lead (Pb-Pb) dating using Secondary Ionization Mass Spectrometry (SIMS) on melt clasts (mainly comprised of pyroxene, plagioclase, ± iron-nickel metal and/or glass) in two eucrites (Serra Pelada and Northwest Africa (NWA) 2696) and phosphates targeted within three mesosiderites (Vaca Muerta, Hainholz, and Estherville), respectively. The eucrite melt clasts yielded ages of 4520 ± 11 Ma and 4528.6 ± 6.3 Ma, in Serra Pelada and NWA 2696, respectively, and are likely indicative of a major heating event, such as an impact, metamorphism due to burial, or prolonged magmatism on the parent body. Our results from targeted mesosiderite phosphate analysis yielded a younger age range of ∼3968 – 4112 Ma, similar to ages reported previously for phosphate analysis in eucrites, as well as the broad range observed previously for many HEDs, and towards the upper end of the age range observed in lunar materials. These data may suggest a period of increased impact flux or possibly several higher-magnitude impacts on the mesosiderite parent body within that timeframe. Our results add further support to the likelihood of the existence of (at least) two different parent bodies for the HEDs (Vesta) and mesosiderites (Mesosiderite Parent Body – MPB).

Characterising water in Lunar and Martian regolith materials using nuclear magnetic resonance

1Keelan T. O’Neill,1Einar Fridjonsson,1Declan Smeed,2Timothy Hopper,1Michael Johns
Icarus (in Press) Link to Article []
1Department of Chemical Engineering, University of Western Australia, Crawley, WA 6009, Australia
2Orebody Intelligence, Orica, 37 Kewdale Rd, Welshpool, WA 6106, Australia
Copyright Elsevier

Water is critical in the future of space exploration and development of planetary bodies. Benchtop nuclear magnetic resonance (NMR) is a geophysical measurement technique with the potential to be used for identification and characterisation of water resources on planetary bodies, such as the Moon and Mars. In this work, we explore the potential of NMR for space exploration by conducting measurements on Lunar and Martian regolith simulants using two main NMR pulse sequences. The first sequence is a decay due to internal fields (DDIF) pulse sequence which probes the pore size of the porous structure created by the regolith simulants. We then use a simple pore-to-particle size model to estimate the particle size distribution of the simulants and validate this against laser particle size analysis (LPSA) data. The DDIF type sequence can also be used to resolve the material surface relaxivity: which is useful in understanding the concentration of paramagnetic species as well as for correlating the length scales of various water volumes. The second pulse sequence utilised is a multi-echo sequence used to quantify fluid volumes as well as total moisture content within the porous media. The fluid volumes observed include adsorbed or hydrated water bound to clay minerals, as well as interparticle water between the regolith simulant grains. The NMR measured moisture content showed reasonably good agreement to corresponding gravimetric measurements used for validation. Finally, we discuss the implications of the current measurements and provide suggested focal points for potential future developments of NMR systems for space exploration.

Searching for mantle dunite candidates around the Imbrium basin among the boulder population using high resolution mineral mapping

1Lingzhi Sun,1Paul G. Lucey
Earth and Planetary Science Letters (in Press) Link to Article []
1Hawai‘i Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, Honolulu, HI 96822, USA
Copyright Elsevier

Dunite is a rock type composed of more than 90% olivine, and Mg-rich dunite has been suggested to be a rock type that may represent upper mantle of the Moon. Dunite rocks might have been exposed on basin rings by basin-forming impacts. However, previous studies reported no unambiguous evidence of mantle dunite from lunar samples and remote sensing detections. In this work, we applied a mantle boulder candidate search algorithm around the Imbrium basin using radiative transfer modeling and datasets from Moon Mineralogy Mapper and Multiband Imager. We found two boulders consisting of ∼90 vol% olivine with 95 Mg# on Copernicus central peaks, which are possible mantle dunite excavated by Imbrium basin or Copernicus crater. We also found that non-dunite boulders on Copernicus central peak show a large variation in olivine content (8–51 vol%). We infer this is a result of the complicated process of Mg-suite formation in the lower crust or mechanical mixing during the Imbrium basin forming event. The algorithm we presented has a great potential to be applied to lunar basins for a global search for mantle candidate boulders.

Petrographic studies and mineralogical characterization of the Dellen impactites

1,2Satu Hietala,3Herbert Henkel,2Jüri Plado
Meteoritics & Planetary Science (in Press) Open Access Lik to Article []
1Geological Survey of Finland, Kuopio, Finland
2Department of Geology, University of Tartu, Tartu, Estonia
3Royal Institute of Technology, Stockholm, Sweden
Published by arrangement with John Wiley & Sons

The impact origin of the Early Cretaceous (140.82 ± 0.51 Ma) 20-km diameter Dellen structure was proven in the late 60s based on the discovery of planar deformation features (PDFs) in quartz grains. Although decades have passed, impactites found from the crater have not received much attention. Thus, this study provides a detailed petrological and mineralogical description of impactites from Dellen. Impactites were classified based on mineralogical observations using the latest recommendations of nomenclature. The studied samples include impact melt rocks (clast rich, clast poor, and clast free), suevitic impact breccias, shocked and unshocked granite, and a shatter cone. Altogether, 16 samples with different lithologies were studied using a polarization microscope. Selected samples were studied with an energy dispersive spectroscopy detector attached to the scanning electron microscopy. PDFs were indexed using a four-axis universal stage from seven samples. Selected samples for PDF studies consisted of clast-rich impact melt rocks (DEL10, DEL13, D99), suevitic impact breccias (DEL14, DEL16, DEL24), and shocked granite target rock (DEL17). A total of 197 PDF sets in 113 quartz grains were studied, and 186 sets resulted in rational crystallographic orientations. Common orientations include π{101̅2}, ω{101̅3}, z{101̅1}, ξ{112̅2}, and {101̅4}. In suevitic impact breccias and impact melt rocks, ballen silica and plagioclase with checkerboard texture were abundant. The petrographic results in Dellen impactites indicate a range of shock pressures from at least 2 to over 60 GPa, based on diagnostic shock metamorphic features in minerals and the occurrence of impact melt rock.

In-situ formation of halite in the Sidi El Habib 001 (H5) ordinary chondrite: Implications for hydrothermal alteration in ordinary chondrite parent bodies

1Shaofan Che,1Kenneth J. Domanik,1,2Thomas J. Zega
Geochimica et Cosmochimica Acta (in Press) Link to Article []
1Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, United States
2Department of Materials Science and Engineering, University of Arizona, Tucson, AZ, United States
Copyright Elsevier

The microstructures and chemistry of secondary feldspars and phosphates in equilibrated ordinary chondrites (OCs) suggest that fluids were involved in the formation of these phases, challenging the conventional view that secondary alteration of equilibrated OCs occur under water-absent conditions. The newly discovered Sidi El Habib 001 (SEH 001), a halite-bearing H5 OC, provides a unique opportunity to further probe the role of fluids during thermal metamorphism on the OC parent bodies. Here we report a petrographic and mineralogic study of SEH 001, with the aim of understanding the origins of halite grains and their implications for the alteration histories of equilibrated OCs. Our investigation reveals a main halite-bearing lithology and a halite-free lithology, both of which show equilibrated textures. Except for halides, no significant textural or compositional differences were observed between halite-bearing and -free lithologies. Halite occurs at all spatial scales in the main lithology and shows clear textures of replacing albitic plagioclase and Cl-apatite. Chlorapatite grains in SEH 001 are Cl-rich and many of them contain elevated amounts of “other” anions.

Our observations suggest that halite grains in SEH 001 formed in situ on the parent body via precipitation from an aqueous fluid. The replacement of plagioclase and Cl-apatite by halite and the equilibrated textures of halite-bearing and halite-free lithologies point to a hydrothermal alteration history where halite formed during advanced thermal metamorphism before the fluid was completely lost. The two lithologies were likely affected by fluids with different Cl concentrations that resulted from heterogeneous distribution of HCl hydrate. Based on comparison to experimental data, halite in SEH 001 could have survived peak metamorphism because of its relatively high thermal stability. Collisional disruption of its original parent body could also facilitate the preservation of halite via release of heat. In the rubble pile model of the OC parent body formation, subsequent accretion of hot fragments into a rubble pile body could have resulted in the blurred boundaries between halite-free and -bearing lithologies now observed in our sample. The occurrence of halite in SEH 001 is clear evidence that aqueous fluids were involved in the alteration of equilibrated OCs.

Combined with previous reports of hydrous minerals (such as phyllosilicates) and other related aqueous products in unequilibrated OCs, our study further suggests that S-type asteroids, the parent bodies of OCs, could be more hydrated than previously thought and might serve as a potential source of water for terrestrial planets in the inner solar system. Nevertheless, whether the proposed hydrothermal history of SEH 001 can be extrapolated to other equilibrated OCs needs to be tested. The in-situ formation origin of halite in SEH 001 contrasts with the exogeneous origin of halite in Monahans (1998) and Zag, suggesting that halites with different origins occurred on the OC parent bodies. The rarity of halite in OCs could be attributed to the heterogeneous distribution of HCl hydrate in the OC parent bodies, although the fragile nature of halite in terrestrial and laboratory environments also increases the likelihood of halite being destroyed in OC samples.