^1,2J. S. New,^1,3R. A. Mathies,²M. C. Price,²M. J. Cole,^1,3M. Golozar,²V. Spathis,²M. J. Burchell,¹A. L. Butterworth
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13448]
¹Space Sciences Laboratory, University of California, Berkeley, 7 Gauss Way, Berkeley, California, 94720 USA
²School of Physical Sciences, University of Kent, Canterbury, Kent, CT2 7NH UK
³Department of Chemistry, University of California, Berkeley, California, 94720 USA
Published by arrangement with John Wiley & Sons

The presence and accessibility of a sub‐ice‐surface saline ocean at Enceladus, together with geothermal activity and a rocky core, make it a compelling location to conduct further, in‐depth, astrobiological investigations to probe for organic molecules indicative of extraterrestrial life. Cryovolcanic plumes in the south polar region of Enceladus enable the use of remote in situ sampling and analysis techniques. However, efficient plume sampling and the transportation of captured organic materials to an organic analyzer present unique challenges for an Enceladus mission. A systematic study, accelerating organic ice‐particle simulants into soft inert metal targets at velocities ranging 0.5–3.0 km s⁻¹, was carried out using a light gas gun to explore the efficacy of a plume capture instrument. Capture efficiency varied for different metal targets as a function of impact velocity and particle size. Importantly, organic chemical compounds remained chemically intact in particles captured at speeds up to ~2 km s⁻¹. Calibration plots relating the velocity, crater, and particle diameter were established to facilitate future ice‐particle impact experiments where the size of individual ice particles is unknown.

^1,2,3Marc Neveu,⁴Christopher H.House,^2,3,5Scott T.Wieman
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2020.113714]
¹Department of Astronomy, University of Maryland, 4296 Stadium Dr., College Park, MD 20742, USA
²Planetary Environments Laboratory, NASA Goddard Space Flight Center, 8800 Greenbelt Rd., Greenbelt, MD 20770, USA
³Center for Research in Space Science and Technology, NASA Goddard Space Flight Center, 8800 Greenbelt Rd., Greenbelt, MD 20770, USA
⁴Department of Geosciences, Pennsylvania State University, 503 Deike Building, University Park, PA 16802, USA
⁵Center for Space Sciences and Technology, University of Maryland, Baltimore County, 1000 Hilltop Cir., Baltimore, MD 21250, USA
Copyright Elsevier

Clark et al. [Clark, R.N., Brown, R.H., Cruikshank, D.P., Swayze, G.A., 2019. Icarus, 321, 791–802] reported an extremely low value of the ¹²C/¹³C ratio in CO₂ ice on Phoebe, a likely captured moon of Saturn. Unless Phoebe did not form in the solar system, we interpret this value as indication that Phoebe accreted surface carbon from a region of the protosolar nebula where ¹³C was enriched due to self-shielding of ¹²CO from photodissociation. This could imply that Phoebe is also enriched in ^17,18O relative to most solar system objects sampled to date. Phoebe and other objects that may have sampled these ¹³C-rich regions, such as Pallas or Triton, may provide the opportunity to directly measure isotopic fractionations in endmembers of the self-shielded solar nebula.

¹Lukáš Ackerman,¹Karel Žák,¹Roman Skála,¹Jan Rejšek,¹Šárka Křížová,²Josh Wimpenny,³Tomáš Magna
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2020.02.025]
¹Institute of Geology of the Czech Academy of Sciences, Rozvojová 269, CZ-165 00 Praha 6, Czech Republic
²Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
³Czech Geological Survey, Klárov 3, CZ-118 21 Praha 1, Czech Republic
Copyright Elsevier

The Australasian tektite (AAT) strewn field is the largest strewn field on the Earth with about ∼10–30% coverage, both land and ocean, but a clearly identified source impact crater is absent despite the young age of AAT of ca. 790 ka. A genetic link between the Australasian tektites and their unequivocal parental materials is therefore largely impossible to establish. Nevertheless, the nature of the parental materials and the extent of volatilization can be constrained using the splash form tektites, carrying the chemical signatures of high-temperature processes, and the layered (so-called Muong Nong-type) tektites, which are less chemically homogenized and exceptionally abundant in the AAT field. New high-precision Sr, Nd and Pb isotopic measurements were obtained for a chemically and petrographically well-characterized suite of AAT, which included the Muong Nong-type (MN-AAT) with precisely known field locations in Laos and splash forms (SF-AAT) from different parts of the strewn field. In addition, optically dark and light zones of the MN-AAT were also separately analyzed. Homogeneous ε_Nd values from −11.8 to −11.2, combined with a narrow range of two-stage Nd model ages from 1.67 to 1.72 Ga for the entire AAT suite, point to a well-mixed source, in terms of REE, of the crustal segment from which the sedimentary material for tektites was ultimately derived. The Sr isotopic data largely overlap for SF-AAT and MN-AAT (⁸⁷Sr/⁸⁶Sr = 0.71636–0.72021) and indicate Paleozoic to Mesozoic sedimentary parentage. However, late Neogene to early Quaternary re-deposition and formation of a thick silt-sized sedimentary section with vertical stratification is required to comply with ¹⁰Be data. Lead isotope systematics documents at least three different components which can perhaps be represented by different mineral phases, such as feldspar, zircon, organic matter adsorbed on young sediments etc., sorted during fluvial transport and final deposition. In addition, the SF-AAT have systematically lower Pb contents than the MN-AAT, and generally show isotopically heavier Pb isotopic ratios. This is theoretically consistent with a preferential volatilization of lighter Pb isotopes during evaporation and considerably larger Pb loss from SF-AAT when compared to MN-AAT. Nevertheless, further experimental work would be necessary to unambiguously distinguish kinetic fractionation from source mixing.

^1,2Sergey N. Britvin,¹Michail N. Murashko,³Yevgeny Vapnik,¹Yury S. Polekhovsky,^1,2Sergey V. Krivovichev,¹Maria G. Krzhizhanovskaya,¹Oleg S. Vereshchagin,^1,4Vladimir V. Shilovskikh,¹Natalia S. Vlasenko
American Mineralogist 105, 428 – 436 Link to Article [https://doi.org/10.2138/am-2020-7275]
¹St. Petersburg State University, Universitetskaya Nab. 7/9, 199034 St. Petersburg, Russia
²Kola Science Center, Russian Academy of Sciences, Fersman Str. 14, 184200 Apatity, Russia
³Department of Geological and Environmental Sciences, Ben-Gurion University of the Negev, P.O.B. 653, Beer-Sheva 84105, Israel
⁴Institute of Mineralogy, Urals Branch of Russian Academy of Science, Miass 456317, Russia
Copyright: The Mineralogical Society of America

This paper is a first detailed report of natural hexagonal solid solutions along the join Fe₂P–Ni₂P. Transjordanite, Ni₂P, a Ni-dominant counterpart of barringerite (a low-pressure polymorph of Fe₂P), is a new mineral. It was discovered in the pyrometamorphic phosphide assemblages of the Hatrurim Formation (the Dead Sea area, Southern Levant) and was named for the occurrence on the Transjordan Plateau, West Jordan. Later on, the mineral was confirmed in the Cambria meteorite (iron ungrouped, fine octahedrite), and it likely occurs in CM2 carbonaceous chondrites (Mighei group). Under reflected light, transjordanite is white with a beige tint. It is non-pleochroic and weakly anisotropic. Reflectance values for four COM recommended wavelengths are [R_max/R_min, % (λ, nm)]: 45.1/44.2 (470), 49.9/48.5 (546), 52.1/50.3 (589), 54.3/52.1 (650). Transjordanite is hexagonal, space group P62m; unit-cell parameters for the holotype specimen, (Ni_1.72Fe_0.27)_1.99P_1.02, are: a = 5.8897(3), c = 3.3547(2) Å, V = 100.78(1) ų, Z = 3. D_calc = 7.30 g/cm³. The crystal structure of holotype transjordanite was solved and refined to R₁ = 0.013 based on 190 independent observed [I > 2σ(I)] reflections. The crystal structure represents a framework composed of two types of infinite rods propagated along the c-axis: (1) edge-sharing tetrahedra [M(1)P₄] and (2) edge-sharing [M(2)P₅] square pyramids. Determination of unit-cell parameters for 12 members of the Fe₂P–Ni₂P solid-solution series demonstrates that substitution of Ni for Fe in transjordanite and vice versa in barringerite does not obey Vegard’s law, indicative of preferential incorporation of minor substituent into M(1) position. Terrestrial transjordanite may contain up to 3 wt% Mo, whereas meteoritic mineral bears up to 0.2 wt% S.

¹Patricia L. Clay,¹Katherine H. Joy,¹Brian O’Driscoll,¹Henner Busemann,¹Lorraine Ruzié-Hamilton,¹Ray Burgess,¹Jonathan Fellowes,²Bastian Joachim-Mrosko,¹John Pernet-Fisher,^3,4Stanislav Strekopytov, ⁵Christopher J. Ballentine
American Mineralogist 105, 289 – 306 Link to Article [https://doi.org/10.2138/am-2020-7237]
¹Department of Earth and Environmental Sciences, University of Manchester, Manchester, M13 9PL, U.K.
²Institute of Mineralogy and Petrography, University of Innsbruck, Innrain 52f, A-6020 Innsbruck, Austria
³Imaging and Analysis Centre, Natural History Museum, Cromwell Road, London, SW7 5BD, U.K.
⁴National Measurement Laboratory, LGC Ltd, Queens Road, Teddington, TW11 0LY, U.K.
⁵Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, OX1 3AN, U.K.
Copyright: The Mineralogical Society of America

Volatile elements (e.g., H, C, N) have a strong influence on the physical and chemical evolution of planets and are essential for the development of habitable conditions. Measurement of the volatile and incompatible heavy halogens, Cl, Br, and I, can provide insight into volatile distribution and transport processes, due to their hydrophilic nature. However, information on the bulk halogen composition of martian meteorites is limited, particularly for Br and I, largely due to the difficulty in measuring ppb-level Br and I abundances in small samples. In this study, we address this challenge by using the neutron irradiation noble gas mass spectrometry (NI-NGMS) method to measure the heavy halogen composition of five olivine-phyric shergottite meteorites, including the enriched (Larkman Nunatak LAR 06319 and LAR 12011) and depleted (LAR 12095, LAR 12240, and Tissint) compositional end-members. Distinct differences in the absolute abundances and halogen ratios exist between enriched (74 to136 ppm Cl, 1303 to 3061 ppb Br, and 4 to 1423 ppb I) and depleted (10 to 26 ppm Cl, 46 to 136 ppb Br, and 3 to 329 ppb I) samples. All halogen measurements are within the ranges previously reported for martian shergottite, nakhlite, and chassignite (SNC) meteorites. Enriched shergottites show variable and generally high Br and I absolute abundances. Halogen ratios (Br/Cl and I/Cl) are in proportions that exceed those of both carbonaceous chondrites and the martian surface. This may be linked to a volatile-rich martian mantle source, be related to shock processes or could represent a small degree of heavy halogen contamination (a feature of some Antarctic meteorites, for example). The differences observed in halogen abundances and ratios between enriched and depleted compositions, however, are consistent with previous suggestions of a heterogeneous distribution of volatiles in the martian mantle. Depleted shergottites have lower halogen abundances and Br and Cl in similar proportions to bulk silicate Earth and carbonaceous chondrites. Tissint in particular, as an uncontaminated fall, allows an estimate of the depleted shergottite mantle source composition to be made: 1.2 ppm Cl, 7.0 ppb Br, and 0.2 ppb I. The resultant bulk silicate Mars (BSM) estimate (22 ppm Cl, 74 ppb Br, and 6 ppb I), including the martian crust and depleted shergottite mantle, is similar to estimates of the bulk silicate earth (BSE) halogen composition.

¹Maksimova, A.A.,²Unsalan, O.,¹Chukin, A.V.,³Karabanalov, M.S.,⁴Jenniskens, P.,⁵Felner, I.,¹Semionkin, V.A.,¹Oshtrakh, M.I.
Spectrochimica Acta – Part A: Molecular abd Biomolecular Spectroscopy 228, 117819 Link to Article [DOI: 10.1016/j.saa.2019.117819]
¹Institute of Physics and Technology, Ural Federal University, Ekaterinburg, 620002, Russian Federation
²Faculty of Science, Department of Physics, Ege University, Bornova, Izmir 35100, Turkey
³Institute of Material Science and Metallurgy, Ural Federal University, Ekaterinburg, 620002, Russian Federation
⁴SETI Institute, Mountain View, CA 94043, United States
⁵Racah Institute of Physics, The Hebrew University, Jerusalem, 91904, Israel

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¹Daniel P. Glavin,¹Jamie E. Elsila,^1,2Hannah L. McLain,^1,2José C. Aponte,¹Eric T. Parker,¹Jason P. Dworkin,⁴Dolores H. Hill,^3,4Harold C. Connolly Jr.,⁴Dante S. Lauretta
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13451]
¹NASA Goddard Space Flight Center, Greenbelt, Maryland, 20771 USA
Catholic University of America, Washington, District of Columbia, 20064 USA
²Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, 85721 USA
³Rowan University, Glassboro, New Jersey, 08028 USA
⁴Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, 85721 USA
Published by arrangement with John Wiley & Sons

The abundances, distributions, enantiomeric ratios, and carbon isotopic compositions of amino acids in two fragments of the Aguas Zarcas CM2 type carbonaceous chondrite fall and a fragment of the CM2 Murchison meteorite were determined via liquid chromatography time‐of‐flight mass spectrometry and gas chromatography isotope ratio mass spectrometry. A suite of two‐ to six‐carbon aliphatic primary amino acids was identified in the Aguas Zarcas and Murchison meteorites with abundances ranging from ~0.1 to 158 nmol/g. The high relative abundances of α‐amino acids found in these meteorites are consistent with a Strecker‐cyanohydrin synthesis on these meteorite parent bodies. Amino acid enantiomeric and carbon isotopic measurements in both fragments of the Aguas Zarcas meteorites indicate that both samples experienced some terrestrial protein amino acid contamination after their fall to Earth. In contrast, similar measurements of alanine in Murchison revealed that this common protein amino acid was both racemic (D ≈ L) and heavily enriched in ¹³C, indicating no measurable terrestrial alanine contamination of this meteorite. Carbon isotope measurements of two rare non‐proteinogenic amino acids in the Aguas Zarcas and Murchison meteorites, α‐aminoisobutyric acid and D‐ and L‐isovaline, also fall well outside the typical terrestrial range, confirming they are extraterrestrial in origin. The detections of non‐terrestrial L‐isovaline excesses of ~10–15% in both the Aguas Zarcas and Murchison meteorites, and non‐terrestrial L‐glutamic acid excesses in Murchison of ~16–40% are consistent with preferential enrichment of circularly polarized light generated L‐amino acid excesses of conglomerate enantiopure crystals during parent body aqueous alteration and provide evidence of an early solar system formation bias toward L‐amino acids prior to the origin of life.

^1,2Sylvain Bouley,³James Tuttle Keane,⁴David Baratoux,⁵Benoit Langlais,⁶Isamu Matsuyama,¹Francois Costard,⁷Roger Hewins,⁸Valerie Payré,⁷Violaine Sautter,¹Antoine Séjourné,⁴Olivier Vanderhaeghe,²Brigitte Zanda

Nature Geoscience 13, 105-109 Link to Article [DOIhttps://doi.org/10.1038/s41561-019-0512-6]

¹GEOPS – Géosciences Paris Sud, Univ. Paris-Sud, CNRS, Université Paris-Saclay, Orsay, France
²IMCCE – Observatoire de Paris, CNRS-UMR 8028, Paris, France
³California Institute of Technology, Pasadena, CA, USA
⁴Geosciences Environnement Toulouse, UMR 5563 CNRS, IRD & Université de Toulouse, Toulouse, France
⁵Laboratoire de Planétologie et Géodynamique, CNRS UMR 6112, Université de Nantes, Université d’Angers, Nantes, France
⁶Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
⁷Institut de Minéralogie, de Physique des Matériaux, et de Cosmochimie (IMPMC) – Sorbonne Université- Muséum National d’Histoire Naturelle, UPMC Université Paris 06, UMR CNRS 7590, IRD UMR 206, Paris, France
⁸Department of Earth, Environmental and Planetary Sciences, Rice University, Houston, TX, USA

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

¹J.I.Simon,^1,2R.Christoffersen,³J.Wang,¹M.D.Mouser,⁴R.D.Mills,^1,2,5D.K.Ross,²Z.Rahman,³C.M.O’D.Alexander
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2020.02.008]
¹Center for Isotope Cosmochemistry and Geochronology, Astromaterials Research and Exploration Science, NASA Johnson Space Center, Houston, TX 77058, USA
²Jacobs, NASA Johnson Space Center, Mail Code XI3, Houston, TX 77058, USA
³Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015-1305, USA
⁴Department of Geological Sciences, University of North Carolina, Chapel Hill, NC 27599, USA
⁵University of Texas at El Paso/Jacobs-JETS, Houston, TX 77058, USA
Copyright Elsevier

In this detailed geochemical, petrological, and microstructural study of felsite clast materials contained in Apollo breccia samples 12013, 14321, and 15405, little evidence was found for relatively enriched reservoirs of endogenic lunar volatiles. NanoSIMS measurements have revealed very low volatile abundances (≤2 to 18 ppm hydrogen) in nominally anhydrous minerals (NAMS) plagioclase, potassic alkali feldspar, and SiO₂ that make up a majority of these felsic lithologies. Yet these mineral assemblages and clast geochemistries on Earth would normally yield relatively high volatiles contents in their NAMS (∼20 to ≥80 ppm hydrogen). This difference is particularly notable in felsite 14321,1062 that exhibits extremely low volatile abundances (≤2 ppm hydrogen) and a relatively low amount of microstructural evidence for shock metamorphism given that it is a clast of the most evolved (∼74 wt. % SiO₂) rock-type returned from the Moon. If taken at face value, ‘wet’ felsic magmas (∼1.2 to 1.7 wt. % water) are implied by the relatively high hydrogen contents of feldspar in felsite clasts in Apollo samples 12013 and 15405, but these results are likely misleading. These felsic clasts have microstructural features indicative of significantly higher shock stress than 14321,1062. These crustal lithologies likely obtained no more water from the lunar interior than the magma body producing 14321,1062. Rather, we suggest hydrogen was enriched in samples 12013 and 15405 by impact induced exchange, and/or partial assimilation of volatiles added to the surface of the Moon by a hydrated impactor (asteroid or comet) or the solar wind. Thus, the best estimate for magmatic water contents of felsic lunar magmas comes from 14321,1062 that leads to a calculated magmatic water content of ≤0.2 wt.%. This dry felsic magma has a slightly greater, but comparable water content to the ancient mafic magmas implied by the other lithologies that we have studied. Based on this and expanding evidence for a significantly dry ancient or early degassed Moon it is likely that some recent estimates (100’s ppm) of the water abundances in the lunar parental magma ocean have been overestimated.

¹G. Avice,¹M. Moreira,²J. D. Gilmour
The Astrophysical Journal 889, 68 Link to Article [DOI
https://doi.org/10.3847/1538-4357/ab5f0c]
¹Unversité de Paris, Institut de physique du globe de Paris, CNRS, F-75005 Paris, France
²Department of Earth and Environmental Science, School of Natural Sciences, University of Manchester, Manchester, M13 9PL, UK

Nucleosynthetic isotopic anomalies in meteorites and planetary objects contribute to our understanding of the formation of the solar system. Isotope systematics of chondrites demonstrate the existence of a physical separation between isotopic reservoirs in the solar system. The isotopic composition of atmospheric xenon (Xe) indicates that its progenitor, U-Xe, is depleted in ¹³⁴Xe and ¹³⁶Xe isotopes relative to solar or chondritic end-members. This deficit supports the view that nucleosynthetic heterogeneities persisted during the solar system formation. Measurements of xenon emitted from comet 67P/Churyumov–Gerasimenko (67P) identified a similar, but more extreme, deficit of cometary gas in these isotopes relative to solar gas. Here we show that the data from 67P demonstrate that two distinct sources contributed xenon isotopes associated with the r-process to the solar system. The h-process contributed at least 29% (2σ) of solar system ¹³⁶Xe. Mixtures of these r-process components and the s-process that match the heavy isotope signature of cometary Xe lead to depletions of the precursor of atmospheric Xe in p-only isotopes. Only the addition of pure p-process Xe to the isotopic mixture brings ¹²⁴Xe/¹³²Xe and ¹²⁶Xe/¹³²Xe ratios back to solar-like values. No pure p-process Xe has been detected in solar system material, and variation in p-process Xe isotopes is always correlated with variation in r-process Xe isotopes. In the solar system, p-process incorporation from the interstellar medium happened before incorporation of r-process nuclides or material in the outer edge of the solar system carries a different mixture of presolar sources as have been preserved in parent bodies.