¹Samuel Ebert,¹Markus Patzek,¹Sarah Lentfort,¹Addi Bischoff
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13407]
¹Institut fur Planetologie, Westfälische Wilhelms-Universität Münster,  Wilhelm-Klemm-Str.10, 48149 Münster, Germany
Published by arrangement with John Wiley & Sons

One approach to decipher the dynamics of material transport and planetary accretion in the early solar system is to investigate xenolithic fragments in meteorites. In this work, we examined an igneous fragment from the NWA 12651 meteorite—the first igneous fragment found in any CM chondrite—by analyzing its mineralogy, rare earth elements (REEs), and O‐isotopes. The study shows that the exsolution lamellae of the igneous fragment consist of Fe‐rich and Ca‐rich pyroxene. Thus, the fragment was part of a progressive crystallization in a closed system, such as in a depleted magma reservoir or mantle. In this environment, the pyroxene co‐crystallized with plagioclase, resulting in a negative Eu anomaly and enrichment of the heavy REEs compared to the light REEs. The O‐isotopes of the fragment are more ¹⁶O‐enriched than the mafic minerals in the matrix or in other bulk CM chondrites; therefore, the fragment was formed in a different region than the NWA 12651 parent body. The iron meteorites Tucson and Deep Springs, the pallasite Milton, and the CB chondrites have similar O‐isotopes as the igneous fragment. However, no direct connection can be drawn and it is questionable if the fragment shares a same parent body with one of these meteorites. The close formation region to the CB chondrites may suggest a formation of the fragment in the carbonaceous chondrite region. Thus, a wide transport through the nebula of the early solar system may not have been necessary to move the fragment to the CM chondrite formation region.

¹Davide Lenaz,²Vanni Lughi,³Diego Perugini,^3,4Maurizio Petrelli,⁵Gianluca Turco,⁶Birger Schmitz
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13400]
¹Department of Mathematics and Geosciences, University of Trieste, 34128 Trieste, Italy
²Department of Engineering and Architecture, University of Trieste, 34127 Trieste, Italy
³Department of Physics and Geology, University of Perugia,06123 Perugia, ltaly
⁴INFN, Sezione di Perugia, 06123 Perugia, Italy
⁵Department of Medical Sciences, University of Trieste,Piazza dell’Ospitale 1, 34125 Trieste, Italy
⁶Astrogeobiology Laboratory, Department of Physics, Lund University, 22100 Lund, Sweden
Published by arrangement with John Wiley & Sons

MgAl₂O₄ spinels from Allende and NWA 763 carbonaceous chondrites were studied by X‐ray single crystal diffraction, SEM, electron microprobe, LA‐ICP‐MS, and Raman spectroscopy. Those from Allende are almost pure, but, in one case, we found a strong FeO_tot zonation. Spinels from NWA 763 show Mg‐Fe²⁺ substitutions. Almost pure MgAl₂O₄ spinels from both meteorites underwent slow cooling and reached their intracrystalline closure temperature (T_c) in the range 460–520 °C. The NWA 763 spinel with higher FeO content shows a T_c of about 720 °C. X‐ray single crystal diffraction and Raman spectroscopy suggest a slow cooling and an ordered structure with trivalent cations in M site and divalent in T site. Among the trace elements, Ti and Co are enriched with respect to the terrestrial analogs, while Mn, Ni, and Sn show intermediate values between different terrestrial occurrences. Vanadium cannot be used as a tracer of extraterrestrial origin as for Cr‐spinels, because its content is similar in extraterrestrial and terrestrial spinels. In the zoned crystal from Allende, Co show a strong zonation similar to that of FeO.

^1,2M.N.DePrá,^3,4J.Licandro,¹N.PinillaAlonso,³V.Lorenzie,²E.Rondón,²J.Carvano,²D.Morate,^3,4J.De León
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2019.113473]
¹Florida Space Institute, University of Central Florida, FL, USA
²Departamento de Astrofísica, Observatório Nacional, Rio de Janeiro, 20921-400, Brazil
³Instituto de Astrofísica de Canarias, C/Vía Láctea s/n, 38205 La Laguna, Spain
⁴Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
⁵Fundación Galileo Galilei – INAF, Rambla José Ana Fernández Pérez, 7, 38712 Breña Baja, Santa Cruz de Tenerife, Spain
Copyright Elsevier

The Lixiaohua collisional family lies in the Outer Main Belt, close to the well characterized Themis primitive class family. It is one of the only three families that host two active asteroids that present cometary-like activity: 313P/ Gibbs and 358P/PANSTARRS (P/2012 T1). As a part of the PRIMitive Asteroid Spectoscopy Survey (PRIMASS), we present the results of a spectroscopic program where we acquired 36 objects in visible wavelengths, using the 4.1 m SOAR, and, 17 objects in the near-infrared, using the 3.58m Telescopio Nazionale Galileo, which provided the characterization of 43 out of the 756 identified Lixiaohua family members. We observed asteroids members of the Lixiaohua family with the aim of: (1) determining the spectral class and spectroscopic properties of the family, (2) estimating the presence of hydrated minerals on their surfaces by studying the 0.7 μm absorption band and the UV drop of reflectance below 0.5 μm, (3) analyzing if active asteroids 358P and 313P are probable family members. Our results show that the Lixiaohua family is consistently redder families than the Themis family and present a wide variety of slopes. We haven’t found an unambiguous trace of aqueous alteration in the spectra of the family members, at the observed wavelengths. Finally, we conclude that the Lixiaohua family is the probable source of the Main-Belt Comets 313P/ Gibbs and 358P/PANSTARRS.

¹J.P.Pabari,¹S.Nambiar,²V.Shah,¹A.Bhardwaj
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2019.113510]
¹PRL, Ahmedabad, India
²CSPIT, Changa, India
Copyright Elsevier

Dust particles exist everywhere in interplanetary space and they evolve dynamically after their origination from the sources like Asteroid belt, Kuiper belt, comets or space debris left during the formation of solar system. These micrometeorites encounter the inner planets, while they spiral-in towards the Sun. From whichever come to Earth, many particles are ablated in the Earth’s atmosphere and leave the metallic ions behind. In case of Moon, all such particles can reach the surface without ablation owing to the absence of atmosphere. Due to the impact of hypervelocity dust particles on lunar surface, ejecta come out in the lunar environment. In some cases, the ejecta velocity could be larger than the escape velocity and particles may be able to escape from Moon. Further, the escaping ejecta may carry water ice (volatiles), whenever incoming projectiles hit the surface in polar region with the water ice present. In this paper, we have computed the ejecta parameters and estimated the possible escape of volatiles from Moon, using Galileo observations of the dust particles near Moon. Considering the incident angle distribution, the upper limit of regolith escape rate is found to be ~2.218 × 10−4 [1.662 × 10−4, 10.232 × 10−4] kg/s. Similarly, the upper limit of water ice escape rate is found to be ~1.988 × 10−7 [1.562 × 10−7, 7.567 × 10−7] kg/s. On one side, Moon is found to be gradually becoming heavier due to its one order higher incoming dust particles than those escaping from it. While on the other side, Moon could be depleted of water ice (volatiles) resources over a period of time, because of the escape due to micrometeorite impact. The results presented here could be useful to understand the dust and volatile escape from Moon.

^1,2,3Zhuang Guo,^1,2 YangLi,²Shen Liu,⁵Huifang Xu,^1,4Shijie Li,^1,4Xiongyao Li,⁶Yangting Lin,⁷Ian M.Coulson,^1,4Mingming Zhang
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2019.10.036]
¹Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
²State Key Laboratory of Continental Dynamics and Department of Geology, Northwest University, Xi’an 710069, China
³University of Chinese Academy of Sciences, Beijing 100049, China
⁴Center for Excellence in Comparative Planetology, Chinese Academy of Sciences, China
⁵Department of Geoscience, University of Wisconsin-Madison, Madison, Wisconsin 53706-1692, USA
⁶Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
⁷Solid Earth Studies Laboratory, Department of Geology, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
Copyright Elsevier

Although pure metallic iron (i.e. that with an Fe content of greater than 99%) commonly occurs in achondrites, and within the returned soil from asteroids or the Lunar surface, it is rarely found in ordinary chondrites meteorites. Abundant nanophase iron particles (np-Fe⁰) were identified in pyroxene glass, within the shock melt vein of Grove Mountains (GRV) 022115, which is an ordinary (L6) chondrite, with a shock stage determined as S5. The association of np-Fe⁰, highly defective high pressure clinoenstatite (HP-CEn), silica glass, as well as vesicles, embedded in a pyroxene glass selvage within the shock melt vein in this meteorite suggests that these phases formed as the result of decomposition of the host pyroxene grain, a process induced by the shock event that affected GRV 022115. The reaction to account for this mineral breakdown can be written as: FeSiO₃ →Fe + SiO₂ + 1/2O₂ ↑ (MgSiO₃ remain in the HP-CEn). The pressure and temperature condition attending this reaction are estimated at 20-23 GPa and over 1800 ℃, as indicated by the surrounded high-pressure mineral assemblage: ringwoodite, majorite, and magnesiowüstite. This study provides evidence to the formation of np-Fe⁰ derived from pyroxene, and HP-CEn quenched metastably in such shocked vein could preserve the metastable phase transitions history record.

¹Ryota Fukaiand,¹Tetsuya Yokoyama
The Astrophysical Journal 879, 79 Link to Article [https://doi.org/10.3847/1538-4357/ab0e0d]
¹Department of Earth and Planetary Sciences, School of Science, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551, Japan

We conducted high-precision Sr and Nd isotopic measurements in bulk chondrites using a complete sample digestion technique. Our new data indicate that enstatite and ordinary chondrites possess uniform and small, but resolvable, Sr and Nd isotopic deviations from terrestrial rocks. In contrast, the Sr isotope ratios varied across different classes of carbonaceous chondrites (CM, CO, and CV). The deviation of data from the s-process mixing line in Sr–Nd isotopic space likely resulted from the incorporation of calcium-aluminum-rich inclusions (CAIs) into carbonaceous chondrite parent bodies. Planetary-scale Sr and Nd isotopic heterogeneities among terrestrial rocks, enstatite, ordinary chondrites, and CAI-subtracted carbonaceous chondrites suggest a heterogeneous distribution of s-process-enriched materials in the early solar system, probably caused by nebular thermal processing. The observed Sr and Nd isotopic variation across the CAI-subtracted carbonaceous chondrites cannot be explained solely by nebular thermal processing, but is likely attributable to s-process-depleted silicate grains that repeatedly circulated among the early solar system. These grains were transferred and incorporated at varying degrees into the formation region of the parent bodies of individual carbonaceous chondrites.

¹Aki Takigawa,²Yoshihiro Furukawa,³Yuki Kimura,⁴ Björn Davidsson,²Tomoki Nakamura
The Astrophysical Journal 881, 27 Link to Article [https://doi.org/10.3847/1538-4357/ab27c6]
¹The Hakubi Center for Advanced Research/Division of Earth and Planetary Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo, Kyoto 606-8502, Japan
²Department of Earth Science, Tohoku University, 6-3 Aza-aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan
³Institute of Low Temperature Science, Hokkaido University, Kita-19, Nishi-8, Kita-ku, Sapporo, 060-0819, Japan
⁴Jet Propulsion Laboratory/California Institute of Technology, M/S183-401, 4800 Oak Ridge Grove Drive, Pasadena, CA 91109, USA

Hydration is a major mineral alteration process in primitive asteroids and it might occur in comet nuclei; however, it is poorly understood at low temperatures, especially below the freezing point of water. Long-duration experiments were performed with exposures of amorphous silicate nanoparticles and organic compounds (glycine and ribose) to D₂O and D₂O + NH₃ ices and vapors at temperatures of −17°C and −27°C for 10–120 days; and with exposure of amorphous silicates to H₂O vapor/liquid at >25°C for 10 days. The amorphous silicates were analyzed by X-ray diffraction and Fourier-transform infrared spectroscopy, and recovery of organic molecules was determined by liquid chromatography–mass spectrometry. No hydration of amorphous silicates or organic compounds was observed after exposure at temperatures below −17°C for 120 days to ices with or without NH₃, whereas hydration of the amorphous silicates was observed in experiments above room temperature. The estimated thermal history of the nucleus of the short-period comet 67P/Churyumov–Gerasimenko indicates that the surface temperature does not exceed −45°C, even in a region exposed to strong solar illumination during the perihelion passage. Assuming hydration is controlled by the collision frequency between H₂O molecules and dust particles, the present results indicate that cometary dust does not hydrate for more than 25–510 periods of comet 67P. This is consistent with the absence of phyllosilicates on 67P and suggests that amino acids and sugars have not been altered.

^1,2Lo, Y.H.,³Liao, C.-T.,¹Zhou, J.,¹Rana, A.,³Bevis, C.S.,³Gui, G.,⁴Enders, B.,⁵Cannon, K.M.,⁴Yu, Y.-S.,⁴Celestre, R.,⁴Nowrouzi, K.,⁴Shapiro, D.,³ Kapteyn, H.,⁴Falcone, R.,⁵Bennett, C.,³Murnane, M.,¹Miao, J.
Science Advances 5, eaax3009 Link to Article [DOI: 10.1126/sciadv.aax3009]
¹Department of Physics and Astronomy, California NanoSystems Institute, University of California, Los Angeles, CA 90095, United States
²Department of Bioengineering, University of California, Los Angeles, CA 90095, United States
³JILA, Department of Physics, University of Colorado, National Institute of Standards and Technology (NIST), Boulder, CO 80309, United States
⁴Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
⁵Department of Physics, University of Central Florida, Orlando, FL 32816, United States

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^1,2,3Nan Liu,^4,5Thomas Stephan,^6,7Sergio Cristallo,⁸Roberto Gallino,^4,5Patrick Boehnke,³Larry R. Nittler,³Conel M. O’D. Alexander,^4,5,9Andrew M. Davis,^4,5,10Reto Trappitsch,^4,5,11Michael J. Pellin,^12,13Iris Dillmann
The Astrophysical Journal 881, 28 Link to Article [https://doi.org/10.3847/1538-4357/ab2d27]
¹Laboratory for Space Sciences and Physics Department, Washington University in St. Louis, St. Louis, MO 63130, USA
²McDonnell Center for the Space Sciences, Washington University in St. Louis, St. Louis, MO 63130, USA
³Department of Terrestrial Magnetism, Carnegie Institution for Science, Washington, DC 20015, USA
⁴Department of the Geophysical Sciences, The University of Chicago, Chicago, IL 60637, USA
⁵Chicago Center for Cosmochemistry, Chicago, IL, USA
⁶INAF-Osservatorio Astronomico d’Abruzzo, Teramo 64100, Italy
⁷INFN-Sezione di Perugia, Perugia 06123, Italy
⁸Dipartimento di Fisica, Università di Torino, Torino 10125, Italy
⁹The Enrico Fermi Institute, The University of Chicago, Chicago, IL 60637, USA
¹⁰Nuclear and Chemical Sciences Division, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
¹¹Materials Science Division, Argonne National Laboratory, Argonne, IL 60439, USA
¹²TRIUMF, 4004 Westbrook Mall, Vancouver, British Columbia V6T 2A3, Canada
¹³Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia V8P 5C2, Canada

We report Mo isotopic compositions of 37 presolar SiC grains of types Y (19) and Z (18), rare types commonly argued to have formed in lower-than-solar metallicity asymptotic giant branch (AGB) stars. Direct comparison of the Y and Z grain data with data for mainstream grains from AGB stars of close-to-solar metallicity demonstrates that the three types of grains have indistinguishable Mo isotopic compositions. We show that the Mo isotope data can be used to constrain the maximum stellar temperatures (T _MAX) during thermal pulses in AGB stars. Comparison of FRUITY Torino AGB nucleosynthesis model calculations with the grain data for Mo isotopes points to an origin from low-mass (~1.5–3 M _⊙) rather than intermediate-mass (>3–~9 M _⊙) AGB stars. Because of the low efficiency of ²²Ne(α, n)²⁵Mg at the low T _MAX values attained in low-mass AGB stars, model calculations cannot explain the large ³⁰Si excesses of Z grains as arising from neutron capture, so these excesses remain a puzzle at the moment.

¹Suttle, M.D.,²Twegar, K.,³Nava, J.,³Spiess, R.,⁴Spratt, J.,^1,5Campanale, F.,¹ Folco, L.
Scientific Reports 9, 12426 Link to Article [DOI: 10.1038/s41598-019-48937-0]
¹Dipartimento di Scienze della Terra, Università di Pisa, Pisa, 56126, Italy
²Department of Chemistry, Istanbul Technological University, Istanbul, 34467, Turkey
³Dipartimento di Geoscienze, Via Gradenigo 6, Padova, 35131, Italy
⁴Department of Earth Science, The Natural History Museum, Cromwell Rd, South Kensington, London, SW7 5BD, United Kingdom
⁵Center for Nanotechnology Innovation@NEST, Istituto Italiano di Tecnologia (IIT), Piazza San Silvestro 12, Pisa, 56127, Italy

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