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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¹Liu, M.-C.,^2,3Han, J.,⁴Brearley, A.J.,¹Hertwig, A.T.
Science Advances 5, eaaw3350 Link to Article [DOI: 10.1126/sciadv.aaw3350]
¹Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, Los Angeles, CA 90095, United States
²Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, TX 77058, United States
³NASA Johnson Space Center, 2101 NASA Parkway, Houston, TX 77058, United States
⁴Department of Earth and Planetary Sciences, MSC03-2040, University of New Mexico, Albuquerque, NM 87131, United States

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¹J. Martin Laming,²Angelos Vourlidas,³Clarence Korendyke,³Damien Chua,⁴Steven R. Cranmer,¹Yuan-Kuen Ko,⁵Natsuha Kuroda,²Elena Provornikova,⁶John C. Raymond,²Nour-Eddine Raouafi
The Astrophysical Journal 879, 124 Link to Article [https://doi.org/10.3847/1538-4357/ab23f1]
¹Space Science Division, Code 7684, Naval Research Laboratory, Washington, DC 20375, USA
²Johns Hopkins University Applied Physics Laboratory, Laurel. MD 20723, USA
³Space Science Division, Code 7686, Naval Research Laboratory, Washington, DC 20375, USA
⁴Department of Astrophysical and Planetary Sciences, Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80309, USA
⁵University Corporation for Atmospheric Research (UCAR), Boulder, CO 80307, USA, and Space Science Division, Code 7684, Naval Research Laboratory, Washington DC 20375, USA
⁶Smithsonian Astrophysical Observatory, Cambridge, MA 02138, USA
⁷NRL/NRC Research Associate, Space Science Division, Code 7684, Naval Research Laboratory, Washington, DC 20375, USA
⁸Space Science Division, Code 7685, Naval Research Laboratory, Washington, DC 20375, USA

We examine the different element abundances exhibited by the closed loop solar corona and the slow speed solar wind. Both are subject to the first ionization potential (FIP) effect, the enhancement in coronal abundance of elements with FIP below 10 eV (e.g., Mg, Si, Fe) with respect to high-FIP elements (e.g., O, Ne, Ar), but with subtle differences. Intermediate elements, S, P, and C, with FIP just above 10 eV, behave as high-FIP elements in closed loops, but are fractionated more like low-FIP elements in the solar wind. On the basis of FIP fractionation by the ponderomotive force in the chromosphere, we discuss fractionation scenarios where this difference might originate. Fractionation low in the chromosphere where hydrogen is neutral enhances the S, P, and C abundances. This arises with nonresonant waves, which are ubiquitous in open field regions, and is also stronger with torsional Alfvén waves, as opposed to shear (i.e., planar) waves. We discuss the bearing these findings have on models of interchange reconnection as the source of the slow speed solar wind. The outflowing solar wind must ultimately be a mixture of the plasma in the originally open and closed fields, and the proportions and degree of mixing should depend on details of the reconnection process. We also describe novel diagnostics in ultraviolet and extreme ultraviolet spectroscopy now available with these new insights, with the prospect of investigating slow speed solar wind origins and the contribution of interchange reconnection by remote sensing.

^1,2,3Daly, L.,¹Lee, M.R.,⁴Piazolo, S.,¹Griffin, S.,⁵Bazargan, M.,^1,6Campanale, F.,¹ Chung, P.,¹Cohen, B.E.,¹Pickersgill, A.E.,¹Hallis, L.J.,⁷Trimby, P.W.,⁸Baumgartner, R.,² Forman, L.V.,^9,10Benedix, G.K.
Science Advances 5, eaaw5549 Link to Article [DOI: 10.1126/sciadv.aaw5549]
¹School of Geographical and Earth Sciences, University of Glasgow, Glasgow, G12 8QQ, United Kingdom
²Space Science and Technology Centre, School of Earth and Planetary Sciences, Curtin University, GPO Box U1987, Perth, WA 6845, Australia
³Australian Centre for Microscopy and Microanalysis, University of Sydney, NSW 2006, Australia
⁴School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, United Kingdom
⁵Department of Earth Sciences, Uppsala University, Uppsala, Sweden
⁶Dipartimento di Scienze della Terra, Università di Pisa ,via Santa Maria 53, Pisa, 56126, Italy
⁷Oxford Instruments Nanoanalysis, High Wycombe, HP12 3SE, United Kingdom
⁸Australian Centre for Astrobiology, University of New South Wales, Sydney, NSW 2052, Australia
⁹Department of Earth and Planetary Sciences, Western Australia Museum, Locked Bag 49, Welshpool, WA 6986, Australia
¹⁰Planetary Science Institute, Suite 106, 1700 East Fort Lowell, Tucson, United States

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^1,2Charles C. Monson,³Dustin Sweet,³Branimir Segvic,³Giovanni Zanoni,²Kyle Balling,^2,4Jacalyn M. Wittmer,⁵G. Robert Ganis,⁶Guo Cheng
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13401]
¹Illinois State Geological Survey, University of lllinois at Urbana-Champaign, 615 East Peabody Drive, Champaign, Illinois
61820, USA
²Department or Geology, University of Illinois at Urbana-Champaign, 1301 West Green Street, Urbana, lllinois 61801, USA
³Department of Geosciences, Texas Tech University, 1200 Memorial Circle, Lubbock, Texas 79409, USA
⁴Department of Geological Sciences, State University of New York at Geneseo, 1 College Circle, Geneseo, New York
14454, USA
⁵Consulting Geologist, 749 Burlwood Drive, Southcrn Pincs. North Carolina 28387, USA
⁶Department of Earth and Environmental Sciences, 115 Trowbridge Hall, Jowa City, Iowa 52242, USA
Published by arrangement with John Wiley & Sons

The Glasford structure in Illinois (USA) was recognized as a buried impact craterin the early 1960s but has never been reassessed in light of recent advances in planetaryscience. Here, we document shatter cones and previously unknown quartz microdeformationfeatures that support an impact origin for the Glasford structure. We identify the 4 kmwide structure as a complex buried impact crater and describe syn- and postimpact depositsfrom its annular trough. We have informally designated these deposits as the KingstonMines unit (KM). The fossils and sedimentology of the KM indicate a marine depositionalsetting. The various intervals within the KM constitute a succession of breccia, carbonate,sandstone, and shale similar to marine sedimentary successions preserved in other craters.Graptolite specimens retrieved from the KM place the time of deposition at approximately4552 Ma (Late Ordovician, Sandbian). This age determination suggests a possible linkbetween the Glasford impact and the Ordovician meteorite shower, an increase in the rateof terrestrial meteorite impacts attributed to the breakup of the L-chondrite parent body inthe main asteroid belt.

¹Larry R. Nittler,²Rhonda M. STROUD, ¹Conel M. O’D. ALEXANDER, ^1,3Kaitlin HOWELL
Meteoritics & Planetary Science (in Press) Link to Article [doi: 10.1111/maps.13397]
¹Department of Terrestrial Magnetism, Carnegie lnstitution of Washington, Washington,District of Columbia 20015, USA
²U.S. Naval Research Laboralory, Codle 6366, 4555 Overlook Ave. SW, Washington, District of Columbia 20375, USA
³Present address: School of Engineering, Ecole Polytechnique Federale de Lausanne, Lausanne CH-1015, Switzerland
Published by arrangement with John Wiley & Sons

We report a correlated NanoSIMS-transmission electron microscopy study of theungrouped carbonaceous chondrite Northwest Africa (NWA) 5958. We identified 10presolar SiC grains, 2 likely presolar graphite grains, and 20 presolar silicate and/or oxidegrains in NWA 5958. We suggest a slight modification of the commonly used classificationsystem for presolar oxides and silicates that better reflects the grains’ likely stellar origins.The matrix-normalized presolar SiC abundance in NWA 5958 is 18þ1510ppm (2r) similar tothat seen in many classes of unmetamorphosed chondrites. In contrast, the matrix-normalized abundance of presolar O-rich phases (silicates and oxides) is 30:9þ17:813:1ppm (2r),much lower than seen in interplanetary dust particles and the least-altered CR, CO, andungrouped C chondrites, but close to that reported for CM chondrites. NanoSIMS mappingalso revealed an unusual13C-enriched (d13C100–200&) carbonaceous rim surrounding a1.4lm diameter phyllosilicate grain. Transmission electron microscopy (TEM) analysis oftwo presolar grains with a likely origin in asymptotic giant branch stars identified one asenstatite and one as Al-Mg spinel with minor Cr. The enstatite grain amorphized rapidlyunder the electron beam, suggesting partial hydration. TEM data of NWA 5958 matrixconfirm that it has experienced aqueous alteration and support the suggestion of Jacquetet al. (2016) that this meteorite has affinities to CM2 chondrites.

¹D. Ray,¹S. Ghosh,²H. Chennaoui Aoudjehane,³S. Das
Meteoritics & Planetary Science (in Prss) Link to Article [doi: 10.1111/maps.13399]
¹Physical Research Laboralory, Ahrnedabad, Gujaral 380 009, lndia
²Facully of Sciences, GAIA Laboralory, Hassan 11 University Casablanca, llP 5366 Maarif, 20000, Casablanca, Morooco
³Department of Metallurgical and Materials Engineering, Indian lnsli_Lulc ofTcchnology’. Kharagpur 721302, lndia
Published by arrangement with John Wiley & Sons

The Agoudal IIAB iron meteorite exhibits only kamacite grains (~6 mm across)without any taenite. The kamacite is homogeneously enriched with numerous rhabditeinclusions of different size, shape, and composition. In some kamacite domains, this appearsfrosty due to micron-scale rhabdite inclusions (~5 to 100lm) of moderate to high Nicontent (~26 to 40 wt%). In addition, all the kamacite grains in matrix are marked with aprominent linear crack formed during an atmospheric break-up event and subsequentlyoxidized. This feature, also defined by trails of lowest Ni-bearing (mean Ni: 23 wt%) mm-scale rhabdite plates (fractured and oxidized) could be a trace of a pre-existingc–ainterface. Agoudal experienced a very slow rate of primary cooling~4°CMa1estimatedfrom the binary plots of true rhabdite width against corresponding Ni wt% and thecomputed cooling rate curves after Randich and Goldstein (1978). Chemically, Agoudaliron (Ga: 54 ppm; Ge: 140 ppm; Ir: 0.03 ppm) resembles the Ainsworth iron, the coarsestoctahedrite of the IIAB group. Agoudal contains multiple sets of Neumann bands that areformed in space and time at different scales and densities due to multiple impacts withshock magnitude up to 130 kb. Signatures of recrystallization due to postshock lowtemperature mild reheating at about 400°C are also locally present.