A robust method to identify meteor showers new parent bodies from the SonotaCo and EDMOND meteoroid orbit databases

1,2M. Guennoun,1J. Vaubaillon,4D. Čapek,4P. Koten,2,3Z. Benkhaldoun
Astronomy & Astrophysics 622, A84 Link to Article [https://doi.org/10.1051/0004-6361/201834593]
1Institut de Mécanique celeste et calcul des Éphémérides, Observatoire de Paris, PSL, France
2Laboratory of High Energy Physics and Astrophysics, Physics Department, Faculty of Science Semlalia, Cadi Ayyad University, PO Box 2390, Marrakesh 40000, Morocco
3Oukaimeden Observatory, Cadi Ayyad University, PO Box 2390, Marrakesh 40000, Morocco
4Astronomical Institute of Academy of Sciences, Fričova 298, 251 65 Ondčejov, Czech Republic

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Detection of carbonates in martian weathering profiles

1Benjamin Bultel,1,2Jean‐Christophe Viennet,3François Poulet,3John Carter,1Stephanie C. Werner
Journal of Geophysical Research Planets (in Press) Link top Article [https://doi.org/10.1029/2018JE005845]
1 Centre for Earth Evolution and Dynamics (CEED), Department for Geosciences, University of Oslo, Norway Oslo, Norway
1 Laboratoire d’Archéologie Moléculaire et Structurale, CNRS UMR 8220, UPMC – 4 place Jussieu, 75005 Paris and Institut de Minéralogie, Physique des Matériaux et Cosmochimie, IMPMC, Sorbonne Universités, CNRS UMR 7590, Muséum National d’Histoire Naturelle, MNHN, UPMC, IRD UMR 206, Paris, France
1 Institut d’Astrophysique Spatiale, Université Paris‐Sud, Orsay, France
Published by arrangement with John Wiley & Sons

Noachian surfaces on Mars exhibit vertical assemblages of weathering horizons termed as weathering profiles; this indicates that surface water caused alteration of the rocks which required a different, warmer climate than today. Evidence of this early martian climate with CO2 vapor as the main component causing greenhouse warming has been challenged by the lack of carbonate in these profiles. Here we report the analysis of CRISM L‐detector data leading to the detections of carbonates using a spectral signature exclusively attributed to them. The carbonates are collocated with hydroxylated minerals in weathering profiles over the martian surface. The origin of CO2 for the formation of carbonates could be the atmosphere. The widespread distribution of weathering profiles with carbonates over the surface of the planet suggest global interactions between fluids containing carbonate/bicarbonate ions with the surface of Mars in the presence of atmospheric water until around 3.7 billion years ago. Please also see the Supporting Information for a graphical abstract.

A radiative heating model for chondrule and chondrite formation

1William Herbst,2James P.Greenwood
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2019.03.039]
1Astronomy Department, Wesleyan University, Middletown, CT 06459, United States of America
2Earth & Environmental Sciences Department, Wesleyan University, Middletown, CT 06459, United States of America
Copyright Elsevier

We propose that chondrules and chondrites formed together during a brief radiative heating event caused by the close encounter of a small (m to km-scale), primitive planetesimal (SPP) with incandescent lava on the surface of a large (100 km-scale) differentiated planetesimal (LDP). In our scenario, chondrite lithification occurs by hot isostatic pressing (HIP) simultaneously with chondrule formation, in accordance with the constraints of complementarity and cluster chondrites. Thermal models of LDPs formed near t = 0 predict that there will be a very narrow window of time, coincident with the chondrule formation epoch, during which crusts are thin enough to frequently rupture by impact, volcanism and/or crustal foundering, releasing hot magma to their surfaces. The heating curves we calculate are more gradual and symmetric than the “flash heating” characteristic of nebular models, but in agreement with the constraints of experimental petrology. The SPP itself is a plausible source of the excess O, Na and Si vapor pressure (compared to a solar nebula environment) that is required by chondrule observations. Laboratory experiments demonstrate that FeO-poor porphyritic olivine chondrules, the most voluminous type of chondrule, can be made using heating and cooling curves predicted by the “flyby” model. If chondrules are a by-product of chondrite lithification, then their high volume abundance within well-lithified chondritic material is not evidence that they were once widespread within the Solar System. Relatively rare events, such as the flybys modeled here, could account for their abundance in the meteorite record.

Planetesimal Population Synthesis: Pebble Flux-regulated Planetesimal Formation

Christian T. Lenz1,3, Hubert Klahr1, and Tilman Birnstiel2
Astrophysical Journal 874, 36 Link to Article [DOI: 10.3847/1538-4357/ab05d9 ]
1Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany
2University Observatory, Faculty of Physics, Ludwig-Maximilians-Universität München, Scheinerstr. 1, D-81679 Munich, Germany
3Member of the International Max Planck Research School for Astronomy and Cosmic Physics at the Heidelberg University.

We propose an expression for a local planetesimal formation rate proportional to the instantaneous radial pebble flux. The result—a radial planetesimal distribution—can be used as an initial condition to study the formation of planetary embryos. We follow the idea that one needs particle traps to locally enhance the dust-to-gas ratios sufficiently, such that particle gas interactions can no longer prevent planetesimal formation on small scales. The locations of these traps can emerge everywhere in the disk. Their occurrence and lifetime is subject to ongoing research; thus, here they are implemented via free parameters. This enables us to study the influence of the disk properties on the formation of planetesimals, predicting their time-dependent formation rates and the location of primary pebble accretion. We show that large α-values of 0.01 (strong turbulence) prevent the formation of planetesimals in the inner part of the disk, arguing for lower values of around 0.001 (moderate turbulence), at which planetesimals form quickly at all places where they are needed for proto-planets. Planetesimals form as soon as dust has grown to pebbles (mm to dm) and the pebble flux reaches a critical value, which is after a few thousand years at 2–3 au and after a few hundred thousand years at 20–30 au. Planetesimal formation lasts until the pebble supply has decreased below a critical value. The final spatial planetesimal distribution is steeper compared to the initial dust and gas distribution, which helps explain the discrepancy between the minimum mass solar nebula and viscous accretion disks.

Modal abundance, density and chemistry of micrometer-sized assemblages by advanced electron microscopy: Application to chondrites

1,2Zanetta, P.-M., 1Le Guillou, C., 1Leroux, H., 2,3,4Zanda, B., 2,3Hewins, R.H., 5Lewin, E., 2Pont, S.
Chemical Geology 514, 27-41 Link to Article [DOI: 10.1016/j.chemgeo.2019.03.025]
1Univ. Lille, CNRS, INRA, ENSCL, UMR 8207 – UMET – Unité Matériaux et Transformations, Lille, F-59000, France
2IMPMC, Sorbonne Université, MNHN, UPMC Paris 06, UMR CNRS 7590, Paris, 75005, France
3EPS, Rutgers Univ., Piscataway, NJ 08854, United States

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Evidence for shock‐induced anhydrite recrystallization and decomposition at the UNAM‐7 drill core from the Chicxulub impact structure

1,2,3T. Salge,3H. Stosnach,4G. Rosatelli,2,5L. Hecht,2,6W. U. Reimold
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13283]
1Natural History Museum, Imaging and Analysis Centre, Cromwell Road, SW7 5BD London, UK
2Museum für Naturkunde, Leibniz‐Institut für Evolutions‐ und Biodiversitätsforschung, Invalidenstrasse 43, 10115 Berlin, Germany
3Bruker Nano GmbH, Am Studio, 12489 Berlin, Germany
4Dipertimento Disputer, Università G. d’Annunzio, 66100 Chieti, Italy
5Institut für Geologische Wissenschaften, Freie Universität Berlin, Malteserstraße 74‐100, 12249 Berlin, Germany
6 Laboratory of Geochronology, Instituto de Geociências, Universidade de Brasília, 70910 900 Brasília, DF, Brazil
Published by arrangement with John Wiley & Sons

Drill core UNAM‐7, obtained 126 km from the center of the Chicxulub impact structure, outside the crater rim, contains a sequence of 126.2 m suevitic, silicate melt‐rich breccia on top of a silicate melt‐poor breccia with anhydrite megablocks. Total reflection X‐ray fluorescence analysis of altered silicate melt particles of the suevitic breccia shows high concentrations of Br, Sr, Cl, and Cu, which may indicate hydrothermal reaction with sea water. Scanning electron microscopy and energy‐dispersive spectrometry reveal recrystallization of silicate components during annealing by superheated impact melt. At anhydrite clasts, recrystallization is represented by a sequence of comparatively large columnar, euhedral to subhedral anhydrite grains and smaller, polygonal to interlobate grains that progressively annealed deformation features. The presence of voids in anhydrite grains indicates SOx gas release during anhydrite decomposition. The silicate melt‐poor breccia contains carbonate and sulfate particles cemented in a microcrystalline matrix. The matrix is dominated by anhydrite, dolomite, and calcite, with minor celestine and feldspars. Calcite‐dominated inclusions in silicate melt with flow textures between recrystallized anhydrite and silicate melt suggest a former liquid state of these components. Vesicular and spherulitic calcite particles may indicate quenching of carbonate melts in the atmosphere at high cooling rates, and partial decomposition during decompression at postshock conditions. Dolomite particles with a recrystallization sequence of interlobate, polygonal, subhedral to euhedral microstructures may have been formed at a low cooling rate. We conclude that UNAM‐7 provides evidence for solid‐state recrystallization or melting and dissociation of sulfates during the Chicxulub impact event. The lack of anhydrite in the K‐Pg ejecta deposits and rare presence of anhydrite in crater suevites may indicate that sulfates were completely dissociated at high temperature (T > 1465 °C)—whereas ejecta deposited near the outer crater rim experienced postshock conditions that were less effective at dissociation.