¹Anicia Arredondo,¹Humberto Campins,²Noemi Pinilla-Alonso,^3,4Juliade León,³Vania Lorenzie,^5,6David Morat,^3,4Juan Luis Rizos,²Mário De Prá
Icarus (in Press) Link to Journal [https://doi.org/10.1016/j.icarus.2021.114619]
¹Physics Department, University of Central Florida, P.O. Box 162385, Orlando, FL 32816, USA
²Florida Space Institute, University of Central Florida, Orlando, FL 32816, USA
³Instituto de Astrofísica de Canarias, Tenerife, Spain
⁴Departamento de Astrofísica, Universidad de La Laguna, 38205 La Laguna, Tenerife, Spain
⁵Fundación Galileo Galilei – INAF, La Palma, Tenerife, Spain
⁶Observatório Nacional, Coordenação de Astronomia e Astrofísica, 20921-400 Rio de Janeiro, Brazil
Copyright Elsevier

We present new near-infrared spectra of 55 objects observed using the NASA InfraRed Telescope Facility and the Telescopio Nazionale Galileo, along with visible spectra of 21 objects obtained from the SMASS and S3OS2 surveys, to explore the differences in spectral slope and curvature between the background and the families and to show that the background is a possible source for both Bennu and Ryugu. Within the background population there is spectral diversity in taxonomy, spectral slope, and absorption band parameters. Our sample of asteroids shows that the background looks spectrally similar to the families in the same region, i.e., the background and families may have originated from the same or similar composition parent bodies. Average band center (0.69 ± 0.02 μm, depth: 2.3 ± 0.9%) of an ~0.7 μm absorption feature attributed to aqueous alteration is present in 30% of our primitive background asteroid sample, similar to abundances observed in other primitive inner belt asteroid families. Both near-Earth asteroid sample return mission targets, (101955) Bennu and (162173) Ryugu, are thought to have originated from primitive asteroid populations in the inner main belt, specifically from the low inclination asteroid families. A population that has not been explored spectrally but is dynamically able to deliver asteroid fragments to near-Earth space is the background population, i.e., asteroids that do not cluster into families. Based on our spectral comparisons, the primordial background is a possible source for (162173) Ryugu, but not for (101955) Bennu.

^1,2H. C Bates,^2,3K. L. Donaldson Hanna,¹A. J. King,²N. E. Bowles,¹S. S. Russell
Journal of Geophysical Research, Planets (in Press) Link to Article [https://doi.org/10.1029/2021JE006827]
¹Department of Earth Sciences, Natural History Museum, London, SW7 5BD UK
²Atmospheric, Oceanic and Planetary Physics, Oxford University, Oxford, OX1 3PU UK
³Department of Physics, University of Central Florida, Orlando, Florida, 32816 US
Published by arrangement with John Wiley & Sons

Volatile-rich asteroids are crucial to understanding the transport of water and organics to the terrestrial planet forming region in the early Solar System. Observations of two such asteroids by Hayabusa2 and OSIRIS-REx suggest a relationship between these bodies and CI, CM and CY chondrites. To confirm this, meteorite spectra need to be collected under appropriate conditions for comparison with asteroid observations. We report mid-infrared (MIR) emissivity spectra (5.5 – 50 µm) obtained under ambient and simulated asteroid environment conditions and near-infrared (NIR) reflectance spectra (2 ‒ 5 µm) of CM and CY chondrite fine-particulate (<35 µm) powders for which bulk mineralogy was determined using X-ray diffraction. Reflectance spectra show a 3 µm feature associated with -OH/H2O that shifts from shorter (∼2.72 µm) to longer (∼2.90 µm) wavelengths and develops a rounder shape and reduced band area with increasing thermal metamorphism. In the MIR, the transparency feature (TF) and features in the Si-O bending region (>15 µm) can be used to infer the relative degree of aqueous alteration, and to resolve the effects of aqueous and thermal alteration, when combined with NIR spectral parameters. The MIR spectra of metamorphosed CY chondrites are distinct from CM chondrite spectra, including a plateau around the Christiansen feature (∼8.00 – 12.50 µm) and features at longer wavelengths in the Si-O bending region (for example, ∼25.50 µm compared to ∼24.30 µm in the CM spectra). We additionally report potential implications of the spectra and parameters determined in this study for the results from Hayabusa2 and OSIRIS-REx.

¹Noriyuki Kawasaki,²Shoichi Itoh,³Naoya Sakamoto,⁴Steven B. Simon,⁵Daiki Yamamoto,^1,3Hisayoshi Yurimoto
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13701]
¹Department of Natural History Sciences, Hokkaido University, Sapporo, 060-0810 Japan
²Department of Earth and Planetary Sciences, Kyoto University, Kyoto, 606-8502 Japan
³Isotope Imaging Laboratory, Creative Research Institution, Hokkaido University, Sapporo, 001-0021 Japan
⁴Institute of Meteoritics, University of New Mexico, Albuquerque, New Mexico, 87131 USA
⁵Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, 252-5210 Japan
Published by arrangement with John Wiley & Sons

Coarse-grained, igneous Ca-Al-rich inclusions (CAIs) in CV chondrites formed through multiple melting events. We conducted in situ O-isotope analysis and Al-Mg systematics by secondary ion mass spectrometry of relict and overgrown minerals from a partial melting event in an Allende Type B CAI, Golfball. Golfball has a Type B CAI bulk composition and a unique structure: a fassaite-rich mantle enclosing a melilite-rich core. Many of the blocky melilite crystals in the core have irregularly shaped, Al-rich (Åk_5–15) cores enclosed in strongly zoned (Åk_30–70) overgrowths. Since the Al-rich melilite grains could not have formed from a melt of Golfball, they are interpreted as relict grains that survived later melting events. The O-isotopic compositions of the blocky melilite crystals plot along the carbonaceous chondrite anhydrous mineral line, ranging between Δ¹⁷O ~ −14‰ and −5‰. The Al-rich relict melilite grains and their overgrowths exhibit the same O-isotopic compositions, while the O-isotopic compositions are varied spatially among melilites. We found that the O-isotopic compositions steeply change across several melilite crystals within few tens of micrometers, indicating the O-isotopic compositions of the melt could not have been homogenized during the partial melting in that scale. According to the time scale of O self-diffusivity in the melt, the cooling rate of the partial melting event is calculated to be >6 × 10⁴ K h⁻¹. Al-Mg isotope data for core minerals plot on a straight line on an Al-Mg evolution diagram. A mineral isochron for Golfball gives initial ²⁶Al/²⁷Al of (4.42 ± 0.20) × 10^–5 and initial δ²⁶Mg* of −0.035 ± 0.050‰. The chemical and O-isotopic compositions of melilite and those initial values imply that its precursor consisted of fluffy Type A and/or fine-grained CAIs. The partial melting event for Golfball may have occurred in very short order after the precursor formation.

¹Alice Aléon-Toppani,¹Rosario Brunetto,²Jérôme Aléon,^1,3,4Zelia Dionnet,¹Stefano Rubino,^1,2Dan Levy,⁵David Troadec,⁶François Brisset,⁷Ferenc Borondics,⁷Andrew King
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13696]
¹Institut d’Astrophysique Spatiale, UMR 8617, CNRS, Univ. Paris-Saclay, Bât 120-121, 91405 Orsay Cedex, France
²Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, UMR 7590, Sorbonne Université, Museum
National d’Histoire Naturelle, CN RS, IRD, 61 rue Buffon, 75005 Paris, France
³INAF-IAPS, Rome, Italy
⁴DIST-Università Parthenope, Naples, Italy
⁵Institut d’électronique de microélectronique et de nanotechnologie, UMR 8520, Laboratoire central, Cité scientifique, Avenue Henri Poincaré, CS, 60069, 59652 Villeneuve d’Ascq Cedex, France
⁶Institut de Chimie Moléculaire et des Matériaux d’Orsay, CNRS, UMR 8182, Univ. Paris-Saclay, Orsay, France
⁷SOLEIL Synchrotron, Gif-sur-Yvette, France
Published by arrangement with John Wiley & Sons

With the recent and ongoing sample return missions and/or the developments of nano- to microscale 3-D and 2-D analytical techniques, it is necessary to develop sample preparation and analysis protocols that allow combination of different nanometer- to micrometer-scale resolution techniques and both maximize scientific outcome and minimize sample loss and contamination. Here, we present novel sample preparation and analytical procedures to extract a maximum of submicrometer structural, mineralogical, chemical, molecular, and isotopic information from micrometric heterogeneous samples. The sample protocol goes from a nondestructive infrared (IR) tomography of ~10 to ~70 µm-sized single grains, which provides the distribution and qualitative abundances of both mineral and organic phases, followed by its cutting in several slices at selected sites of interest for 2-D mineralogical analysis (e.g., transmission electron microscopy), molecular organic and mineral analysis (e.g., Raman and/or IR microspectroscopy), and isotopic/chemical analysis (e.g., NanoSIMS). We also discuss here the importance of the focused ion beam microscopy in the protocol, the problems of sample loss and contamination, and at last the possibility of combining successive different analyses in various orders on the same micrometric sample. Special care was notably taken to establish a protocol allowing correlated NanoSIMS/TEM/IR analyses with NanoSIMS performed first. Finally, we emphasize the interest of 3-D and 2-D IR analyses in studying the organics–minerals relationship in combination with more classical isotopic and mineralogical grain characterizations.

¹Kun Wang(王昆),²Weiqiang Li,²Shilei Li,¹Zhen Tian,¹Piers Koefoed,³Xin-Yuan Zheng
Chemie der Erde [Geochemistry] (in Press) Link to Article [https://doi.org/10.1016/j.chemer.2021.125786]
¹Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University in St. Louis, MO 63130, USA
²School of Earth Sciences and Engineering, Nanjing University, Nanjing, Jiangsu 210023, China
³Department of Earth and Environmental Sciences, University of Minnesota – Twin Cities, Minneapolis, MN 55455, USA

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

¹Jan L.Hellmann,^1,2Timo Hopp,¹Christoph Burkhardt,³Harry Becker,^1,4Mario Fischer-Gödde,¹Thorsten Kleine
Geochimica et Cosmochimcia Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2021.06.038]
¹Institut für Planetologie, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Straße 10, 48149 Münster, Germany
²Origins Laboratory, Department of the Geophysical Sciences and Enrico Fermi Institute, The University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60637, USA
³Institut für Geologische Wissenschaften, Freie Universität Berlin, Malteserstraße 74-100, 12249 Berlin, Germany
⁴Institut für Geologie und Mineralogie, Universität zu Köln, Zülpicher Straße 49b, 50674 Köln, Germany
Copyright Elsevier

Tellurium stable isotope compositions and abundances (δ^128/126Te relative to SRM 3156) are reported for 43 ordinary, enstatite, and Rumuruti chondrites, which together with results from a companion study on carbonaceous chondrites are used to assess the origin of volatile element fractionations in chondrites. Whereas Te isotope variations among carbonaceous chondrites predominantly reflect mixing between isotopically light chondrules/chondrule precursors and CI-like matrix, Te isotope variations among non-carbonaceous chondrites mainly result from Te redistribution during parent body thermal metamorphism. The enstatite chondrites in particular display increasingly heavy Te isotopic compositions and decreasing Te concentrations with increasing degree of metamorphism, indicating migration of isotopically light Te from the strongly metamorphosed inner parts towards the cooler outer regions of the parent bodies. By contrast, ordinary and Rumuruti chondrites display less systematic Te isotope variations, implying more localized redistribution of Te during parent body thermal metamorphism.

We also report Te stable isotope data for 19 terrestrial mantle-derived rocks. Peridotites with Al₂O₃ contents close to those inferred for the bulk silicate Earth (BSE) exhibit uniform δ^128/126Te values, which we interpret to represent the Te isotopic composition of the BSE. This composition overlaps with the Te isotope composition of some volatile-rich carbonaceous chondrites (most notably CM chondrites), but also with that of enstatite chondrites. Comparison of the Te results to Se isotopes and Se/Te ratios shows that due to uncertainties in the composition of the BSE and the isotopic composition of bulk chondrite parent bodies, neither Te isotopes alone nor the combined Se-Te elemental and isotopic systematics can distinguish between a carbonaceous and enstatite chondrite-like late veneer, which is the presumed source of Se and Te in the BSE. Together, the results of this study illustrate that the relative abundances and mass-dependent isotope compositions of volatile elements like Se and Te are modified by physical and chemical processes occurring after planetary accretion, which severely complicates their use as genetic tracers. A corollary of this is that contrary to prior proposals the Se-Te systematics are not contradicting an inner solar system origin of the late veneer, as it has been inferred using nucleosynthetic isotope anomalies of other elements.

^1,2Roger Hewins et al. (>10)
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2021.06.035]
¹IMPMC, Sorbonne Univ, MNHN, UPMC Paris 06, UMR CNRS 7590, 75005 Paris, France
²EPS, Rutgers Univ, Piscataway, NJ 08854, USA
Copyright Elsevier

Many asteroids in the main belt have spectra like those of Mighei-type CM chondrites, but some Near Earth Objects (NEO) resemble less well known types of C2 chondrite. Northwest Africa (NWA) 12563, a new find with affinities to C2 chondrites, could help us understand the differences between observations of CM2 chondrites and bodies that are currently being studied by the Hayabusa 2 and Osiris-Rex space missions. NWA 12563 contains 14% chondrules supported by 86% fine grained matrix consistent with CM2 chondrites, but differs from them in other respects. In both matrix and chondrules, olivine is unaltered and pyroxene shows incipient alteration. Metal in chondrules is pseudomorphed by serpentine, and mesostasis is replaced by serpentine- saponite and chlorite. Many Type I chondrules have highly irregular shapes resulting from fracturing and selective metal replacement. Type II porphyritic chondrules are clusters of phenocrysts set in matrix-like material. Type II chondrules may be kinked and partially disbarred. The matrix of NWA 12563 differs from CM2 chondrites in the absence of tochilinite-cronstedtite intergrowths. It contains hydrated and oxidized amorphous silicate (Fe3+/∑Fe ∼75%) richer in magnesium than in other chondrites (with embedded sulfides). Serpentine-saponite is also present, as well as abundant framboidal magnetite.

NWA 12563 has similarities to a number of ungrouped magnetite-rich and 18O-rich chondrites (Bells, Essebi, Niger I, WIS 91600, Tagish Lake, and MET 00432) that we call C2-ung1, as opposed to C2-ung2 chondrites (poorer in 18O and magnetite). The oxygen isotopic composition coupled with a magnetic susceptibility of log χ = 4.67 places NWA 12563 with these ungrouped chondrites in a cluster distinct from CM2 chondrites. NWA 12563 is closest to WIS 91600 among the C2-ung1 chondrites in alteration style and light element compositions. WIS 91600, however, has suffered light thermal metamorphism, suggesting that NWA 12563 might represent its altered but unheated precursor material within the same parent body if it were zoned. The average Vis-NIR spectrum of NWA 12563 matches the asteroid taxonomic class K and resembles that of CO3 Frontier Mountain (FRO) 95002, but its spectra range from very “red” in dark matrix areas and very “blue” in magnetite-rich areas. The average MIR spectrum shows features indicating phyllosilicates, aliphatic CH compounds, hydrated silicates, and olivine. It is significantly different from those of other chondrites including FRO 95002, and closest to Bells (from which it differs in carbon isotopic composition) and WIS91600. The variety of mineralogical, chemical and isotopic properties among C2-ung1 chondrites requires several different parent bodies. However, the high abundance of magnetite common to this cluster of ungrouped chondrites, and to a lesser extent CI chondrites, indicates that they should be considered as possible material from Bennu, which has an 18 µm magnetite signal in its spectrum not seen in the CM2 chondrites (Hamilton et al., 2019).

¹C.M.Lisse et al. (>10)
The Astrophysical Journal 894, 116 Link to Article [DOI https://doi.org/10.3847/1538-4357/ab7b80]
¹ JHU-APL, 11100 Johns Hopkins Road, Laurel, MD 20723, USA; carey.lisse@jhuapl.edu, ron.vervack@jhuapl.edu

We report here time-domain infrared spectroscopy and optical photometry of the HD 145263 silica-rich circumstellar-disk system taken from 2003 through 2014. We find an F4V host star surrounded by a stable, massive 1022–1023 kg (MMoon to MMars) dust disk. No disk gas was detected, and the primary star was seen rotating with a rapid ~1.75 day period. After resolving a problem with previously reported observations, we find the silica, Mg-olivine, and Fe-pyroxene mineralogy of the dust disk to be stable throughout and very unusual compared to the ferromagnesian silicates typically found in primordial and debris disks. By comparison with mid-infrared spectral features of primitive solar system dust, we explore the possibility that HD 145263’s circumstellar dust mineralogy occurred with preferential destruction of Fe-bearing olivines, metal sulfides, and water ice in an initially comet-like mineral mix and their replacement by Fe-bearing pyroxenes, amorphous pyroxene, and silica. We reject models based on vaporizing optical stellar megaflares, aqueous alteration, or giant hypervelocity impacts as unable to produce the observed mineralogy. Scenarios involving unusually high Si abundances are at odds with the normal stellar absorption near-infrared feature strengths for Mg, Fe, and Si. Models involving intense space weathering of a thin surface patina via moderate (T < 1300 K) heating and energetic ion sputtering due to a stellar super-flare from the F4V primary are consistent with the observations. The space-weathered patina should be reddened, contain copious amounts of nanophase Fe, and should be transient on timescales of decades unless replenished.

¹Alexey Potapov,¹Cornelia Jäger,²Thomas Henning
The Astrophysical Journal 894, 110 Link to Article [DOI https://doi.org/10.3847/1538-4357/ab86b5]
¹Laboratory Astrophysics Group of the Max Planck Institute for Astronomy at the Friedrich Schiller University Jena, Institute of Solid State Physics, Helmholtzweg 3, D-07743 Jena, Germany; alexey.potapov@uni-jena.de
²Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany

The catalytic role of dust grain surfaces in the thermal reaction CO2 + 2NH3 → NH4+NH2COO− was recently demonstrated by our group. The rate coefficients for the reaction at 80 K on the surface of nanometer-sized carbon and silicate grains were measured to be up to three times higher compared to the reaction rate coefficients measured on KBr. In this study, the reaction was performed on carbon grains and on KBr in the extended temperature range of 50–80 K and with the addition of water ice. The reaction activation energy was found to be about three times lower on grains compared to the corresponding ice layer on KBr. Thus, the catalytic role of the dust grain surface in the studied reaction can be related to a reduction of the reaction barrier. Addition of water to NH3:CO2 ice on grains slowed the reaction down. At the H2O:CO2 ratio of 5:1, the reaction was not detected on the experimental timescale. This result calls into question the thermal formation of ammonium carbamate in dense molecular clouds and outer regions of protostellar and protoplanetary environments with dominating water ice mantle chemistry. However, it can still happen in inner regions of protostellar and protoplanetary environments in crystalline ices.

¹Florian Kirchschlager,¹M. J. Barlow,¹Franziska D. Schmidt
The Astrophysical Journal 893, 70 Link to Article [DOI https://doi.org/10.3847/1538-4357/ab7db8]
¹Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK; f.kirchschlager@ucl.ac.uk

Core-collapse supernovae can condense large masses of dust post-explosion. However, sputtering and grain–grain collisions during the subsequent passage of the dust through the reverse shock can potentially destroy a significant fraction of the newly formed dust before it can reach the interstellar medium. Here we show that in oxygen-rich supernova remnants like Cassiopeia A, the penetration and trapping within silicate grains of the same impinging ions of oxygen, silicon, and magnesium that are responsible for grain surface sputtering can significantly reduce the net loss of grain material. We model conditions representative of dusty clumps (density contrast of χ = 100) passing through the reverse shock in the oxygen-rich Cassiopeia A remnant and find that, compared to cases where the effect is neglected as well as facilitating the formation of grains larger than those that had originally condensed, ion trapping increases the surviving masses of silicate dust by factors of up to two to four, depending on initial grain radii. For higher density contrasts (χ gsim 180), we find that the effect of gas accretion on the surface of dust grains surpasses ion trapping, and the survival rate increases to ~55% of the initial dust mass for χ = 256.