Amaya Moro-Martín
Astrophysical Journal 866, 131 Link to Article [DOI: 10.3847/1538-4357/aadf34]
Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218, USA

1I/’Oumuamua is the first interstellar interloper to have been detected. Because planetesimal formation and ejection of predominantly icy objects are common by-products of the star and planet formation processes, in this study we address whether 1I/’Oumuamua could be representative of this background population of ejected objects. The purpose of the study of its origin is that it could provide information about the building blocks of planets in a size range that remains elusive to observations, helping to constrain planet formation models. We compare the mass density of interstellar objects inferred from its detection to that expected from planetesimal disks under two scenarios: circumstellar disks around single stars and wide binaries, and circumbinary disks around tight binaries. Our study makes use of a detailed study of the PanSTARRS survey volume; takes into account that the contribution from each star to the population of interstellar planetesimals depends on stellar mass, binarity, and planet presence; and explores a wide range of possible size distributions for the ejected planetesimals, based on solar system models and observations of its small-body population. We find that 1I/’Oumuamua is unlikely to be representative of a population of isotropically distributed objects, favoring the scenario that it originated from the planetesimal disk of a young nearby star whose remnants are highly anisotropic. Finally, we compare the fluxes of meteorites and micrometeorites observed on Earth to those inferred from this population of interstellar objects, concluding that it is unlikely that one of these objects is already part of the collected meteorite samples.

¹Potin, S.,¹Brissaud, O., ^1,2Beck, P., Schmitt, B., ¹Magnard, Y., ¹Correia, J.-J., ¹Rabou, P., ¹Jocou, L.
Applied Optics 57, 8279-8296 Link to Article [https://doi.org/10.1364/AO.57.008279]
¹University Grenoble Alpes, CNRS, Institut de Planétologie et d’Astrophysique de Grenoble, Grenoble, 38000, France
²Institut Universitaire de France, Paris, France

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Minako HASHIGUCHI^1* and Hiroshi NARAOKA^1,2
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13211]
¹Research Center for Planetary Trace Organic Compounds, Kyushu University, Motooka 744, Nishi-ku,Fukuoka 819-0395, Japan
²Department of Earth and Planetary Sciences, Kyushu University, Motooka 744, Nishi-ku, Fukuoka 819-0395, Japan
*Corresponding author. E-mail: hashiguchi.minako.123@m.kyushu-u.ac.jp
Published by arrangement with John Wiley & Sons

High‐resolution mass spectrometry (HRMS) imaging by desorption electrospray ionization (DESI) coupled with Orbitrap MS using methanol (MeOH) spray was performed on a fragment of the Murchison (CM2) meteorite in this study. Homologues of C_nH_2n–1N₂⁺(n = 7–9) and C_nH_2nNO⁺ (n = 9–14) were detected on the sample surface by the imaging. A high‐performance liquid chromatography (HPLC)/HRMS analysis of MeOH extracts from the sample surface after DESI/HRMS imaging indicated that the C_nH_2n–1N₂⁺ homologues corresponds to alkylimidazole, and that a few isomers of the C_nH_2nNO⁺ homologues present in the sample. The alkylimidazoles and C_nH_2nNO⁺ homologues displayed different spatial distributions on the surface of the Murchison fragment, indicating chromatographic separation effects during aqueous alteration. Moreover, the distribution pattern of compounds is also different among homologues. This is probably also resulting from the separation of isomers by similar chromatographic effects, or different synthetic pathways. Alkylimidazoles and the C_nH_2nNO⁺ homologues are mainly distributed in the matrix region of the Murchison by mineralogical observations, which is consistent with previous reports. Altered minerals (e.g., Fe‐oxide, Fe‐sulfide, and carbonates) occurred in this region. However, no clear relationship was found between these minerals and the organic compounds detected by DESI/HRMS imaging. Although this result might be due to scale differences between the spatial resolution of DESI/HRMS imaging and the grain size in the matrix of the Murchison, our results would indicate that alkylimidazoles and the C_nH_2nNO⁺ homologues in the Murchison fragment were mainly synthesized by different processes from hydrothermal alteration on the parent body.

Tao Chen^1,2
Astrophysical Journal 866, 113 Link to Article [DOI: 10.3847/1538-4357/aae38f]
¹Leiden University, Leiden Observatory, Niels Bohrweg 2, NL-2333 CA Leiden, Netherlands
²School of Engineering Sciences in Chemistry, Biotechnology and Health, Department of Theoretical Chemistry & Biology, Royal Institute of Technology, SE-10691, Stockholm, Sweden

Photo-/ion-induced ionization and dissociation processes are commonly observed for polycyclic aromatic hydrocarbon (PAH) molecules. This work performs theoretical studies of PAHs and their fragments. Molecular dynamics simulations in combination with static quantum chemical calculations reveal that following a single hydrogen atom loss, the fragments, PAH-H, are extremely reactive. They catch a neighbor molecule within picoseconds to form a covalently bonded large molecule regardless of orientations/angles and temperatures. We calculate the infrared spectra of the covalently bonded molecules, which indicate that such species could be the carrier of unidentified infrared emission bands. It also implies that regular PAHs might be less abundant in space than what is expected.

¹Cavosie, A.J., ¹Timms, N.E., ²Ferrière, L., ³Rochette, P.
Geology 46, 891-894 Link to Article [DOI: 10.1130/G45079.1]
¹Space Science Technology Centre and The Institute for Geoscience Research (TIGeR), School of Earth and Planetary Science, Curtin University, Perth, WA 6102, Australia
²Natural History Museum, Burgring 7, Vienna, A-1010, Austria
³Aix-Marseille Univ, CNRS, INRA, IRD, Coll. France, CEREGE, Aix-en-Provence, 13545, France

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David V. BEKAERT^1*, Yves MARROCCHI¹, Alex MESHIK², Laurent REMUSAT³, and Bernard MARTY¹
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13213]
¹Centre de Recherches Petrographiques et Geochimiques, CRPG-CNRS, Universite de Lorraine, UMR 7358, 15 rue NotreDame des Pauvres, BP 20, 54501 Vandoeuvre-les-Nancy, France
²Department of Physics, Washington University, 1 Brookings Drive, Saint Louis, Missouri 63130, USA
³Institut de Mineralogie, de Physique des Materiaux et de Cosmochimie (IMPMC), UMR CNRS 7590 – Sorbonne, Universites -UPMC – IRD – Museum National d’Histoire Naturelle, 57 rue Cuvier, Case 52, 75231 Paris Cedex 5, France
Published by arrangement with John Wiley & Sons

The Paris carbonaceous chondrite represents the most pristine carbonaceous chondrite, providing a unique opportunity to investigate the composition of early solar system materials prior to the onset of significant aqueous alteration. A dual origin (namely from the inner and outer solar system) has been demonstrated for water in the Paris meteorite parent body (Piani et al. 2018). Here, we aim to evaluate the contribution of outer solar system (cometary‐like) water ice to the inner solar system water ice using Xe isotopes. We report Ar, Kr, and high‐precision Xe isotopic measurements within bulk CM 2.9 and CM 2.7 fragments, as well as Ne, Ar, Kr, and Xe isotope compositions of the insoluble organic matter (IOM). Noble gas signatures are similar to chondritic phase Q with no evidence for a cometary‐like Xe component. Small excesses in the heavy Xe isotopes relative to phase Q within bulk samples are attributed to contributions from presolar materials. CM 2.7 fragments have lower Ar/Xe relative to more pristine CM 2.9 fragments, with no systematic difference in Xe contents. We conclude that Kr and Xe were little affected by aqueous alteration, in agreement with (1) minor degrees of alteration and (2) no significant differences in the chemical signature of organic matter in CM 2.7 and CM 2.9 areas (Vinogradoff et al. 2017). Xenon contents in the IOM are larger than previously published data of Xe in chondritic IOM, in line with the Xe component in Paris being pristine and preserved from Xe loss during aqueous alteration/thermal metamorphism.

J. Bliss¹, A. Arcones^1,2, and Y.-Z. Qian^3,4
Astrophysical Journal 866, 105 Link to Article [DOI: 10.3847/1538-4357/aade8d]
¹Institut für Kernphysik, Technische Universität Darmstadt, Schlossgartenstr. 2, Darmstadt D-64289, Germany
²GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstr. 1, Darmstadt D-64291, Germany
³School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
⁴Tsung-Dao Lee Institute, Shanghai 200240, People’s Republic of China

The origin of the so-called p-isotopes and in the solar system remains a mystery, as several astrophysical scenarios fail to account for them. In addition, data on presolar silicon carbide grains of type X (SiC X) exhibit peculiar Mo patterns, especially for . We examine the production of Mo and Ru isotopes in neutrino-driven winds associated with core-collapse supernovae (CCSNe) over a wide range of conditions. We find that proton-rich winds can make dominant contributions to the solar abundance of and significant contributions to those of ⁹⁶Ru, ⁹²Mo, and ⁹⁴Mo. In contrast, neutron-rich winds make negligible contributions to the solar abundances of ^92,94Mo and cannot produce ^96,98Ru, whereas the early ejecta of CCSNe can make dominant contributions to the solar abundance of ⁹²Mo. Furthermore, we show that some neutron-rich winds can account for the peculiar Mo patterns in SiC X grains. Our results can be generalized if conditions similar to those studied here are also obtained for other types of ejecta in either CCSNe or neutron star mergers.

Ian U. Roederer^1,2, Charli M. Sakari³, Vinicius M. Placco^2,4, Timothy C. Beers^2,4, Rana Ezzeddine^2,5, Anna Frebel^2,5, and Terese T. Hansen⁶
Astrophysical Journal 865, 129 Link to Article [DOI: 10.3847/1538-4357/aadd92]
¹Department of Astronomy, University of Michigan, 1085 S. University Ave., Ann Arbor, MI 48109, USA
²Joint Institute for Nuclear Astrophysics—Center for the Evolution of the Elements (JINA-CEE), USA
³Department of Astronomy, University of Washington, Seattle, WA 98195-1580, USA
⁴Department of Physics, University of Notre Dame, Notre Dame, IN 46556, USA
⁵Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
⁶Carnegie Observatories, Pasadena, CA 91101, USA

We present a detailed abundance analysis of the bright (V = 9.02), metal-poor ([Fe/H] = −1.47 ± 0.08) field red horizontal-branch star HD 222925, which was observed as part of an ongoing survey by the R-Process Alliance. We calculate stellar parameters and derive abundances for 46 elements based on 901 lines examined in a high-resolution optical spectrum obtained using the Magellan Inamori Kyocera Echelle spectrograph. We detect 28 elements with 38 ≤ Z ≤ 90; their abundance pattern is a close match to the solar r-process component. The distinguishing characteristic of HD 222925 is an extreme enhancement of r-process elements ([Eu/Fe] = +1.33 ± 0.08, [Ba/Eu] = −0.78 ± 0.10) in a moderately metal-poor star, so the abundance of r-process elements is the highest ([Eu/H] = −0.14 ± 0.09) in any known r-process-enhanced star. The abundance ratios among lighter (Z ≤ 30) elements are typical for metal-poor stars, indicating that production of these elements was dominated by normal Type II supernovae, with no discernible contributions from Type Ia supernovae or asymptotic giant branch stars. The chemical and kinematic properties of HD 222925 suggest it formed in a low-mass dwarf galaxy, which was enriched by a high-yield r-process event before being disrupted by interaction with the Milky Way.

¹Senesi, G.S., ²Manzari, P., ³Consiglio, A., ¹De Pascale, O.
Journal of Analytical Atomic Spectroscopy 33, 1664-1675 Link to Article [DOI: 10.1039/c8ja00224j]
¹CNR-Istituto di Nanotecnologia (NANOTEC) PLasMI Lab, Via Amendola 122/D, Bari, 70126, Italy
²Istituto Nazionale di Astrofisica-Istituto di Astrofisica e Planetologia Spaziali (INAF-IAPS), Via Fosso del Cavaliere 100, Roma, Italy
³CNR-Istituto di Tecnologie Biomediche (ITB), Via Amendola 122/D, Bari, 70126, Italy

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Jose C. APONTE^1,2*, Hannah K. WOODWARD^2,3, Neyda M. ABREU⁴, Jamie E. ELSILA¹, and Jason P. DWORKIN¹
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13216 ]
¹Solar System Exploration Division, Code 691, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA
²Department of Chemistry, Catholic University of America, Washington, DC 20064, USA
³Department of Chemistry, University of Reading, Reading RG6 6UA, UK
⁴Earth Science Program, Pennsylvania State University—Du Bois Campus, Du Bois, Pennsylvania 15801, USA
Published by arrangement with John Wiley & Sons

The water‐soluble organic compounds in carbonaceous chondrite meteorites constitute a record of the synthetic reactions occurring at the birth of the solar system and those taking place during parent body alteration and may have been important for the later origins and development of life on Earth. In this present work, we have developed a novel methodology for the simultaneous analysis of the molecular distribution, compound‐specific δ¹³C, and enantiomeric compositions of aliphatic monocarboxylic acids (MCA) extracted from the hot‐water extracts of 16 carbonaceous chondrites from CM, CR, CO, CV, and CK groups. We observed high concentrations of meteoritic MCAs, with total carbon weight percentages which in some cases approached those of carbonates and insoluble organic matter. Moreover, we found that the concentration of MCAs in CR chondrites is higher than in the other meteorite groups, with acetic acid exhibiting the highest concentration in all samples. The abundance of MCAs decreased with increasing molecular weight and with increasing aqueous and/or thermal alteration experienced by the meteorite sample. The δ¹³C isotopic values of MCAs ranged from −52 to +27‰, and aside from an inverse relationship between δ¹³C value and carbon straight‐chain length for C₃–C₆ MCAs in Murchison, the ¹³C‐isotopic values did not correlate with the number of carbon atoms per molecule. We also observed racemic compositions of 2‐methylbutanoic acid in CM and CR chondrites. We used this novel analytical protocol and collective data to shed new light on the prebiotic origins of chondritic MCAs.