^1,2Meng-Hua Zhu,^2,3,4Natalia Artemieva,⁵Alessandro Morbidelli,⁶Qing-Zhu Yin,⁷Harry Becker,^2,7Kai Wünnemann
Nature 571, 226–229 Link to Article [DOI https://doi.org/10.1038/s41586-019-1359-0]
¹State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Taipa, Macau, China
²Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, Berlin, Germany
³Planetary Science Institute, Tucson, AZ, USA
⁴Institute of Geosphere Dynamics, RAS, Moscow, Russia
⁵Département Lagrange, University of Nice–Sophia Antipolis, CNRS, Observatoire de la Côte d’Azur, Nice, France
⁶Department of Earth and Planetary Sciences, University of California at Davis, Davis, CA, USA
⁷Institute für Geologische Wissenschaften, Freie Universität Berlin, Berlin, Germany

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

^1,2Christoph Burkhardt,² Nicolas Dauphas,³ Ulrik Hans,⁴Bernard Bourdon,¹Thorsten Kleine
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2019.07.003]
¹Institut für Planetologie, University of Münster, Wilhelm Klemm-Straße 10, D-48149 Münster, Germany
²Origins Laboratory, Department of the Geophysical Sciences and Enrico Fermi Institute, The University of Chicago, 5734 South Ellis Avenue, Chicago, Illinois 60637, USA
³EMPA, Laboratory for Advanced Materials and Surfaces, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland
⁴Laboratoire de Géologie de Lyon, ENS Lyon, CNRS and Université Claude Bernard Lyon 1, 69364 Lyon cedex 07, France
Copyright Elsevier

Isotope anomalies among planetary bodies provide key constraints on planetary genetics and the Solar System’s dynamical evolution. However, to unlock the full potential of these anomalies for constraining the processing, mixing, and transport of material in the disk it is essential to identify the main components responsible for producing planetary-scale isotope variations, and to investigate how they relate to the isotopic heterogeneity inherited from the Solar System’s parental molecular cloud. To address these issues we measured the Ti and Sr isotopic compositions of Ca,Al-rich inclusions (CAIs) from the Allende CV3 chondrite, as well as acid leachates and an insoluble residue from the Murchison CM2 chondrite, and combine these results with literature data for presolar grains, hibonites, chondrules, and bulk meteorites. Our analysis reveals that the internal mineral-scale nebular isotopic heterogeneity as sampled by leachates and presolar grains is largely decoupled from the planetary-scale isotope anomalies as sampled by bulk meteorites. We show that variable admixing of CAI-like refractory material to an average inner solar nebula component can explain the planetary-scale Ti and Sr isotope anomalies and the elemental and isotopic difference between non-carbonaceous (NC) and carbonaceous (CC) nebular reservoirs for these elements.
Combining isotope anomaly data for a large number of elements (Ti, Sr, Ca, Cr, Ni, Zr, Mo, Ru, Ba, Nd, Sm, Hf, W, and Os) reveals that the offset of the CC from the NC reservoir towards the composition of CAIs is a general trend and not limited to refractory elements. This implies that the CC reservoir is the product of mixing between NC material and a reservoir (called IC for Inclusion-like Chondritic component) whose isotopic composition is similar to that of CAIs, but whose chemical composition is similar to bulk chondrites. In our preferred model, the distinct isotopic compositions of these two nebular reservoirs reflect an inherited heterogeneity of the solar system’s parental molecular cloud core, which therefore has never been fully homogenized during collapse. Planetary-scale isotopic anomalies are thus caused by variable mixing of isotopically distinct primordial disk reservoirs, the selective processing of these reservoirs in different nebular environments, and the heterogeneous distribution of the thereby forming nebular products.

¹Robbin Visser,¹Timm John,²Markus Patzek,²Addi Bischoff,³Martin J.Whitehouse
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2019.06.046]
¹Freie Universität Berlin, Institut für Geologische Wissenschaften Berlin, Germany
²Institut für Planetologie, WWU Münster, Münster, Germany
³Swedish Museum of Natural History, Stockholm, Sweden
Copyright Elsevier

Deciphering aspects of the solar system’s formation process and the origin of planetary bodies can be achieved by examining primitive solar system materials, as these materials reflect the early solar system composition and may represent the building blocks of planetary bodies. Along these lines, knowing the original composition of carbonaceous chondrite meteorites is a valuable asset for determining the conditions in the parent bodies where they formed. Therefore, to determine the key characteristics of the parent bodies from which the carbonaceous chondrites and primitive materials are derived, we examined chemical and sulfur isotope compositions of sulfides in CM, CI and C2ung carbonaceous chondrites as well as from CM- and CI-like volatile-rich clasts; such an investigation allows us to explore the origin of these sulfides and to determine the primordial S composition of their parent body source region. In this study, sulfides from 7 CM, CI, and C2ung carbonaceous chondrites and 16 chondritic and achondritic breccias containing volatile-rich clasts were analyzed by electron microprobe and SIMS. Different sulfides were found, which shows evidence of different formation origins. Based on compositions and exsolution textures, we suggest that one fraction of the sulfides in both clasts and chondrites formed at high temperatures prior to incorporation into the parent body. The other sulfides most likely have a secondary origin and precipitated during fluid–rock interaction. Furthermore, differences in the S isotopic signature of the sulfides in chondrites correlate with the degree of aqueous alteration of the carbonaceous host rocks (CM or CI). Studying the sulfides of the volatile-rich clasts in brecciated chondrites and achondrites, a similar fractionation cannot be seen. Even though the mineralogy of CI chondrites and CI-like clasts is similar, the sulfides in CI chondrites appear to be enriched in heavy isotopes compared to those in the clasts (δ34S +1‰ (CI) vs -2‰ (CI-like clast). This could have been caused by different alteration conditions, or it represents a different sampling reservoir. In this study a large S isotopic fractionation between pentlandite and pyrrhotite was found in large primarily formed sulfides showing exsolution textures, indicating that pentlandite prefers to incorporate light S isotopes. Considering the S isotope composition of the exsolved phase which can be found in CM- and CI-like clasts, the pristine δ34S value of the original monosulfide solid solution (mss) is estimated to be ∼-2‰. This value possibly resembles the sampling reservoir from which the sulfides formed, indicating that both CM- and CI-like clasts derived from a similar reservoir, and this reservoir is different from the formation reservoir of the CI chondrites.

¹Imene Kerraouch,²Samuel Ebert,²Markus Patzek,²Addi Bischoff,³Michael E.Zolensky,⁴Andreas Pack,^6,7 Philippe Schmitt-Kopplin,¹Djelloul Belhai,¹Abderrahmane Bendaoud,⁷Loan Le
Geochemistry (Chemie der Erde) (in Press) Link to Article [https://doi.org/10.1016/j.chemer.2019.06.002]
¹LGGIP, FSTGAT, Université des Sciences et de la Technologie Houari Boumediene, Alger, Algeria
²Institut für Planetologie, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm Str. 10, D-48149 Münster, Germany
³ARES, NASA Johnson Space Center, Houston, TX, USA
⁴Universität Göttingen, Geowissenschaftliches Zentrum, Goldschmidtstr. 1, D-37077 Göttingen, Germany
⁵Helmholtz-Zentrum, München, German Research Center for Environmental Health, Analytical BioGeoChemistry, Ingolstädter Landstraße 1, D-85764 Neuherberg, Germany
⁶Chair of Analytical Food Chemistry, Technische Universität München, D-85354 Freising-Weihenstephan, Germany
⁷Jacobs ESCG, Houston, TX 77058, USA
Copyright Elsevier

The main mineralogical characteristics of a large light-colored clast within the Murchison CM breccia are discussed in detail including data on the mineralogy, bulk chemistry, organics, and oxygen isotopes. Petrographic study shows that the white clast consists of two areas with different granoblastic textures: (1) a coarse-grained (average grain size: ˜200 μm) and (2) a fine-grained lithology (average grain-size: ˜20 μm). The Fa-content of olivine in the clast is the same as Fa within olivine from Rumuruti (R) chondrites (Fa: ˜38 mol%); however, the concentrations of the elements Ni and Ca in olivine are significantly different. The fragment also contains Ca-rich pyroxene, ˜An_30-38-plagioclase/maskelynite, Cr-rich spinel, several sulfide phases, a nepheline-normative glass, and traces of merrillite and metal. The occurrence of maskelynite and nepheline-normative amorphous phase in restricted areas of the well-recrystallized rock may indicate remarkable P-T-excursions during shock metamorphism. The O-isotope composition of the clast falls below the terrestrial fractionation line (TFL), lying in the field of CM chondrites and is significantly different from data for bulk R chondrites. The study of the soluble organic matter revealed a highly-oxidized carbon chemistry and organomagnesium compounds reflecting high temperature and pressure processes.

¹B.Carry et al. (>10)
Astronomy & Astrophysics 623, A132 Link to Article [https://doi.org/10.1051/0004-6361/201833898]
¹Observatoire de la Côte d’Azur: Nice, Provence-Alpes-Côte d’Azu
Reproduced with permission (C) ESO

Context. CM-like asteroids (Ch and Cgh classes) are a major population within the broader C-complex, encompassing about 10% of the mass of the main asteroid belt. Their internal structure has been predicted to be homogeneous, based on their compositional similarity as inferred from spectroscopy and numerical modeling of their early thermal evolution.
Aims. Here we aim to test this hypothesis by deriving the density of the CM-like asteroid (41) Daphne from detailed modeling of its shape and the orbit of its small satellite.
Methods. We observed Daphne and its satellite within our imaging survey with the Very Large Telescope extreme adaptive-optics SPHERE/ZIMPOL camera and complemented this data set with earlier Keck/NIRC2 and VLT/NACO observations. We analyzed the dynamics of the satellite with our Genoid meta-heuristic algorithm. Combining our high-angular resolution images with optical lightcurves and stellar occultations, we determine the spin period, orientation, and 3D shape, using our ADAM shape modeling algorithm.
Results. The satellite orbits Daphne on an equatorial, quasi-circular, prograde orbit, like the satellites of many other large main-belt asteroids. The shape model of Daphne reveals several large flat areas that could be large impact craters. The mass determined from this orbit combined with the volume computed from the shape model implies a density for Daphne of 1.77 ± 0.26 g cm−3 (3 σ). This densityis consistent with a primordial CM-like homogeneous internal structure with some level of macroporosity (≈ 17%).
Conclusions. Based on our analysis of the density of Daphne and 75 other Ch/Cgh-type asteroids gathered from the literature, we conclude that the primordial internal structure of the CM parent bodies was homogeneous.

¹H.Haack et al (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13344]
¹Maine Mineral and Gem Museum, 99 Main St., Bethel, Maine, 04217 USA
Published by arrangement with John Wiley & Sons

On February 6, 2016 at 21:07:19 UT, a very bright fireball was seen over the eastern part of Denmark. The weather was cloudy over eastern Denmark, but many people saw the sky light up—even in the heavily illuminated Copenhagen. Two hundred and thirty three reports of the associated sound and light phenomena were received by the Danish fireball network. We have formed a consortium to describe the meteorite and the circumstances of the fall and the results are presented in this paper. The first fragment of the meteorite was found the day after the fall, and in the following weeks, a total of 11 fragments with a total weight of 8982 g were found. The meteorite is an unbrecciated, weakly shocked (S2), ordinary H chondrite of petrologic type 5/6 (Bouvier et al. 2017). The concentration of the cosmogenic radionuclides suggests that the preatmospheric radius was rather small ~20 cm. The cosmic ray exposure age of Ejby (83 ± 11 Ma) is the highest of an H chondrite and the second highest age for an ordinary chondrite. Using the preatmospheric orbit of the Ejby meteoroid (Spurny et al. 2017) locations of the recovered fragments, and wind data from the date of the fall, we have modeled the dark flight (below 18 km) of the fragments. The recovery location of the largest fragment can only be explained if aerodynamic effects during the dark flight phase are included. The recovery location of all other fragments are consistent with the dark flight modeling.

¹David Čapek,¹Pavel Koten,¹Jiří Borovička,¹Vlastimil Vojáček,¹Pavel Spurný,¹Rostislav Štork
Astronomy & Astrophysics 625, A106 Link to Article [https://doi.org/10.1051/0004-6361/201935203]
¹Astronomical Institute of the Czech Academy of Sciences, Fričova 298, 251 65 Ondřejov, Czech Republic
Reproduced with permission (C) ESO

Context. A significant fraction of small meteors are produced by iron meteoroids. Their origin and the interaction with the atmosphere have not been well explained up to now.

Aims. The goals of the study are to observe faint, slow, low altitude meteors, to identify candidates for iron meteoroids among them, to model their ablation and light curves, and to determine their properties.

Methods. Double station video observations were used for the determination of atmospheric trajectories, heliocentric orbits, light curves, and spectra of meteors. Meteors with iron spectra or of suspected iron composition based on beginning heights and light curves were modeled. The immediate removal of liquid iron from the surface as a cloud of droplets with Nukiyama–Tanasawa size distribution and their subsequent vaporization was assumed as the main ablation process on the basis of our previous work. The numerical model has only five parameters: meteoroid initial velocity v_∞, zenith distance z, initial mass m_∞, mean drop size D_dr, and luminous efficiency τ. The theoretical light curves were compared with the observed ones.

Results. The model is able to explain the majority of the selected light curves, and meteoroid parameters that are not directly observable – m_∞, D_dr, and τ – are determined. Unlike in most meteor studies, the mass and luminous efficiency are determined independently. Luminous efficiency ranges from 0.08 to 5.8%; it weakly decreases with increasing initial meteoroid mass. No simple dependency on initial velocity was found. The mean size of iron drops depends on the meteoroid velocity. Slower meteoroids can produce drops with a wide range of mean sizes, whereas faster ones are better matched with larger drops with a smaller dispersion of sizes.

^1,7Alian Wang,²Z.C.Ling,^1,7Y.C.Yan,³Alfred S.McEwen,⁴Michael T.Mellon,⁵Michael D.Smith,^1,7Bradley L.Jolliff,⁶JamesHead
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2019.06.024]
¹Department of Earth and Planetary Sciences, Washington University in St. Louis, St. Louis, MO 63130, USA
²Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, Institute of Space Sciences, Shandong University, Weihai 264209, China
³Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA
⁴Cornell Center for Astrophysics and Planetary Science, Cornell University, Ithaca, NY 14850, USA
⁵NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
⁶Department of Earth, Environmental and Planetary Sciences, Brown University, RI 02912, USA
⁷The McDonnell Center for the Space Sciences, Washington University in St. Louis, St. Louis, MO 63130, USA
Copyright Elsevier

We report laboratory experimental results that support a brine-related hypothesis for the recurring slope lineae (RSL) on Mars in which the subsurface Cl-salts, i.e., hydrous chlorides and oxychlorine salts (HyCOS) are the potential source materials. Our experiments revealed that within the observed RSL temperature window T_RSL (250–300 K), the deliquescence of HyCOS could occur in relative humidity ranges (RH ≥ 22%–46%) much lower than those for hydrous (Mg, Fe)-sulfates (RH ≥ 75%–96%). In addition, we demonstrated that the RH values kept by common HyCOS and hydrous sulfates in enclosures have a general trend as RH_sulfates > RH_perchlorates > RH_chlorides (with same type of cation) in wide T range. It means that the required RH range for a Cl-bearing salt to deliquescence can be satisfied by a co-existing salt of different type, e.g., in the subsurface layers of mixed salts on Mars. Furthermore, we found a strong temperature dependence of the deliquescence rates for all tested HyCOS, e.g., a duration of 1–5 sols for all HyCOS at the high end (300 K) of T_RSL, and of 20–70 sols for all tested HyCOS (except NaClO₄·H₂O) at the low end (250 K) of T_RSL, which is consistent with the observed seasonal behavior of RSL on Mars. From a mass-balance point of view, the currently observed evidences on Mars do not support a fully-brine-wetted track model, thus we suggest a brine-triggered granular-flow model for the most RSL. Considering the recurrence of RSL in consecutive martian years, our experimental results support the rehydration of remnant HyCOS layers during a martian cold season through H₂O vapor-to-salt direct interaction. We found that the evidences of HyCOS rehydration under Mars relevant P-T-RH conditions are detectable in a few minutes by in situ Raman spectroscopy. This rehydration would facilitate the recharge of H₂O back into subsurface HyCOS, which could serve as the source material to trigger RSL in a subsequent warm season. The major limiting factor for this rehydration is the H₂O supply, i.e., the H₂O vapor density carried by current Mars atmospheric circulation and the diffusion rate of H₂O vapor into the salt-rich subsurface in a cold season. In a worst-case scenario, these H₂O supplies can support a maximum increase of hydration degrees of two for totally dehydrated HyCOS, whereas the full rehydration of subsurface HyCOS layers can be easily reached during a >30° obliquity period that has H₂O vapor density 10× to 20× times the value of current obliquity. Overall, our results imply the existence of a large amount of Cl-bearing salts in the subsurface at RSL sites.

¹Li Q.,¹Dai W.,^1,2,3Liu B.S.,⁴Sarre P.J.,⁵Xie M.H.,¹Cheung A.S-C.
Molecular Astrophysics 13, 22-29 Link to Article [https://doi.org/10.1016/j.molap.2018.09.002]
¹Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China
²Department of Chemistry, Tianjin University, Tianjin 300072, China
³The National Collaborative Innovative Center of Chem. Sci. Eng. Tianjin, Tianjin 300072, China
⁴School of Chemistry, The University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom
⁵Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong, China

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¹Hyun Na Kim,²Changkun Park,²Sun Young Park,²Hwayoung Kim,¹Min Sik Kim
Journal of Geophysical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2019JE005998]
¹Department of Earth and Environmental SciencesKongju National University, Gongju, Republic of Korea
²Division of Polar Earth‐System Sciences, Korea Polar Research Institute, Incheon, Republic of Korea
Published by arrangement with John Wiley & Sons

Determining the formation mechanism of maskelynite is essential to understanding the shocked environments of meteorites on their parent bodies. Maskelynite has been accepted as a diaplectic glass for several decades, but there have been suggestions that it is a normal glass quenched from a dense melt. Morphological characteristics have been generally investigated to identify the formation mechanism of amorphous plagioclase in meteorites, but the chemical difference between crystalline and amorphous plagioclase has not been fully understood. In this study, we investigated the morphological, atomic‐scale structural, and chemical characteristics of amorphous plagioclase in the lunar meteorite DEW 12007 to constrain its formation mechanism via chemical analysis. The morphological characteristics showed that plagioclase was partially converted into amorphous phase through partial melting. Two‐dimensional Raman mapping confirmed the structural difference between amorphous and crystalline regions. Quantitative chemical analyses revealed that the amorphous regions were more albite‐rich than the crystalline regions, likely due to the partial melting of plagioclase. Under shocked conditions, the partial melting of plagioclase induced a chemical variation between amorphous and crystalline regions. The morphological and structural changes correspond well with the chemical variations, indicating that amorphization induced such variations. The chemical differences between amorphous and crystalline plagioclase in other meteorites also could be understood to be the results of partial melting. Thus, the chemical differences between amorphous and crystalline plagioclase in partially amorphized grains could elucidate the formation mechanism of amorphous plagioclase in many meteorites.