¹Jean‐Pierre Lorand^2,3,4Jabrane Labidi,⁴Claire Rollion‐Bard,⁵Emilie Thomassot,⁶Jeremy J. Bellucci,⁷Martin Whitehouse,⁷Alexander Nemchin,⁸Munir Humayun,³James Farquhar,^9,10Roger H. Hewins,⁹Brigitte Zanda,⁹Sylvain Pont
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13564]
¹Laboratoire de Planétologie et Géodynamique à Nantes, CNRS, UMR 6112, Université de Nantes, 2 Rue de la Houssinère, BP 92208, 44322 Nantes Cédex 3, France
²Geophysical Laboratory, Carnegie Institution of Washington, Washington, District of Columbia, 20015 USA
³Department of Geology, University of Maryland, College Park, Maryland, 20740 USA
⁴Institut de physique du globe de Paris, CNRS, Université de Paris, F‐75005 Paris, France
⁵CRPG‐CNRS, Nancy, 54500 France
⁶Department of Applied Geology, Curtin University, Perth, Western Australia, 6845 Australia
⁷Laboratory for Isotope Geology, Swedish Mus. of Nat History, Stockholm, SE‐104 05 Sweden
⁸Department of Earth, Ocean & Atmospheric Science and National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida, 32310 USA
⁹Institut 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, 61 rue Buffon, 75005 Paris, France
¹⁰Department of Earth & Planetary Sciences, Rutgers University, Piscataway, New Jersey, 08854 USA
Published by arrangement with John Wiley & Sons

The sulfur isotope budget of Martian regolith breccia (NWA 7533) has been addressed from conventional fluorination bulk rock analyses and ion microprobe in situ analyses. The bulk rock analyses yield 865 ± 50 ppm S in agreement with LA‐ICP‐MS analyses. These new data support previous estimates of 80% S loss resulting from terrestrial weathering of NWA 7533 pyrite. Pyrite is by far the major S host. Apatite and Fe oxyhydroxides are negligible S carriers, as are the few tiny igneous pyrrhotite–pentlandite sulfide grains included in lithic clasts so far identified. A small nonzero Δ33S (−0.029 ± 0.010‰) signal is clearly resolved at the 2σ level in the bulk rock analyses, coupled with negative CDT‐normalized δ34S (−2.54 ± 0.10‰), and near‐zero Δ36S (0.002 ± 0.09‰). In situ analyses also yield negative Δ33S values (−0.05 to −0.30‰) with only a few positive Δ33S up to +0.38‰. The slight discrepancy compared to the bulk rock results is attributed to a possible sampling bias. The occurrence of mass‐independent fractionation (MIF) supports a model of NWA 7533 pyrite formation from surface sulfur that experienced photochemical reaction(s). The driving force that recycled crustal S in NWA 7533 lithologies—magmatic intrusions or impact‐induced heat—is presently unclear. However, in situ analyses also gave negative δ34S values (+1 to −5.8‰). Such negative values in the hydrothermal setting of NWA 7533 are reflective of hydrothermal sulfides precipitated from H2S/HS‐ aqueous fluid produced via open‐system thermochemical reduction of sulfates at high temperatures (>300 °C).

¹Ramakant R. Mahajan
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13565]
¹Physical Research Laboratory, Ahmedabad, Gujarat, 380009 India
Published by arrangement with John Wiley & Sons

Noble gases and nitrogen are investigated in eight individual chondrules of the Dhajala H3.8 chondrite. The mean cosmic ray exposure age of the chondrules using 21Ne and 38Ar is 5.9 ± 3.0 Ma. There is no significant evidence of a pre‐exposure for these chondrules. All the measured chondrules contain variable amounts of radiogenic 129Xe. Noble gas analysis indicates Q‐type gas incorporated in the chondrules. The chondrules have variable amounts of N2. The chondrules have distinct trapped N isotopic composition (δ15Nt varies from −24.1 ± 8.4‰ to 89.1 ± 12.7‰), which is inconsistent with Q‐gas and solar wind. These inconsistencies can be considered preliminary evidence in support of multiple trapped components in the chondrules. A heavy N signature component is observed in the chondrules studied contrasted with the solar wind composition. There is no correlation between the concentration of N2 and noble gases. Derivations of variable nitrogen observed in Dhajala (H3.8) chondrules reflect the gas captured at the time of formation, having heterogeneous isotopic signature in the nebula.

¹Mizuho Koike,^2,3Yuji Sano,^1,2Naoto Takahat,⁴ Tsuyoshi Iizuka,^4,5Haruka Ono,^4,5Takashi Mikouchi
Earth and Planetary Science Letters 549, 116497 Link to Article [https://doi.org/10.1016/j.epsl.2020.116497]
¹Earth and Planetary Systems Science Program, Graduate School of Advanced Science and Engineering, Hiroshima University, 1-3-1 Kagamiyama, Higashihiroshima-shi, Hiroshima, 739-8526, Japan
²Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, 277-8564, Japan
³Institute of Surface-Earth System Science, Tianjin University, Nankai District, Tianjin, 300072, PR China
⁴Department of Earth and Planetary Science, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan
⁵The University Museum, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan
Copyright Elsevier

The late heavy bombardment (LHB) hypothesis, wherein the terrestrial planets are thought to have suffered intense collisions ca. 3.9 billion years ago, is under debate. Coupled with new dynamical calculations, re-examination of geochronological data seem to support an earlier solar system instability and a smooth monotonic decline in impacts, as opposed to a “cataclysm.” To better understand this collisional history, records from the asteroidal meteorites are required. Here, we report a uranium–lead (U–Pb) chronological dataset for eucrite meteorites thought to originate from the asteroid 4 Vesta; this dataset indicates to a continuous history of collisions prior to 4.15 Ga. Our 207Pb⁎/206Pb⁎ model ages of apatite [Ca5(PO4)3(F,Cl,OH)] and merrillite [Ca9NaMg(PO4)7] from three brecciated basaltic eucrites—Juvinas (4150.3 ± 11.6 million years ago (Ma); merrillite only), Camel Donga (disturbed around 4570–4370 Ma), and Stannern (4143.0 ± 12.5 Ma)—record multiple thermal metamorphic events during the period of ∼4.4–4.15 Ga. We interpret this to mean that Vesta or the vestoid cluster underwent multiple impacts and moderate high-temperature reheating during this time. The ages of ∼4.4–4.15 Ga are distinctly younger than the initial magmatic process on Vesta (>4.5 Ga) but are significantly older than a later “impact peak” based on some interpretations of 40Ar–39Ar chronologies (∼3.9–3.5 Ga). The intense collisions prior to 4.15 Ga on Vesta are at odds with the conventional LHB hypothesis but not inconsistent with the much earlier bombardment and monotonic decline scenario. Different radiometric chronologies of the asteroid likely represent the different stages of a continual collisional process. Conversely, the model 207Pb⁎/206Pb⁎ ages of apatite in the unbrecciated basaltic eucrite, Agoult, returned an age of 4524.8 ± 9.6 Ma. This may represent slow cooling from an earlier global reheating of the crust on Vesta at 4.55 Ga, as documented by other radiometric chronologies. The apatite in Juvinas recorded a coincident timing of 4516.9 ± 10.4 Ma, which could be due to either slow crustal cooling or impact.

¹Giampaolo P. Sighinolfi,^1,2Federico Lugli,¹Federica Piccione,³Vincenzo DE Michele,^1,4Anna Cipriani
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13550]
¹Department of Chemical and Geological Sciences, University of Modena and Reggio Emilia, Via Campi 103, Modena, 41225 Italy
²Department of Cultural Heritage, University of Bologna, Via degli Ariani 1, Ravenna, 48121 Italy
³Museo di Storia Naturale, Milan, 20121 Italy
⁴Lamont‐Doherty Earth Observatory, Columbia University, Palisades, New York, 10964 USA
Published by arrangement with john Wiley & Sons

Strontium isotopes and selected trace elements (Rb, Sr, REE, Zr, Hf, Th, and U) were measured on samples of Libyan Desert Glass (LDG) and a series of terrestrial materials (rocks, LDG‐bearing soils, eolic sand) collected over a large area of southwestern Egypt to identify the LDG terrestrial parent material and the site where impact melting occurred. Samples include Upper Cretaceous hypersilicic sandstones outcropping at or near the LDG strewn field and Lower Cretaceous to Silurian sandstones from the Gilf Kebir Plateau highlands. Strontium isotopes and partially Zr, Hf, Th, and U, possibly reflecting the composition of detrital zircon grains, are effective indicators of the geochemical affinity between terrestrial materials and LDG, unlike Rb, Sr, and REE abundances. The best geochemical affinity with LDG was found in LDG‐bearing soils collected at the base of intradunal corridors in the Great Sand Sea. Remarkably, abundances of the Zr group elements of the LDG Zr‐bearing phase are distinct from all terrestrial detrital zircons from the area. We suggest a mixture of weathering products from sandstones of different ages, including Devonian and Silurian rocks from the Gilf Kebir highlands, as the most likely source for LDG. A loose sedimentary formation exposed 29 Ma ago at the Earth’s surface, superimposed over hard bedrock, might have been the true terrestrial target of the impact, but because of its incoherent nature, it was rapidly destroyed, explaining the complete absence of any evidence of an impact structure.

^1,2James S. New,³Bahar Kazemi,²Mark C. Price,²Mike J. Cole,²Vassi Spathis,^1,3Richard A. Mathies,²Anna L. Butterworth
Meteoritics & Planetary Science (in Press) Link to Articie [https://doi.org/10.1111/maps.13554]
¹Space Sciences Laboratory, University of California, 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

Enceladus is a compelling destination for astrobiological analyses due to the presence of simple and complex organic constituents in cryovolcanic plumes that jet from its subsurface ocean. Enceladus plume capture during a flyby or orbiter mission is an appealing method for obtaining pristine ocean samples for scientific studies of this organic content because of the high science return, reduced planetary protection challenges, and lower risk and expense compared to a landed mission. However, this mission profile requires sufficient amounts of plume material for sensitive analysis. To explore the feasibility and optimization of the required capture systems, light gas gun experiments were carried out to study organic ice particle impacts on indium surfaces. An organic fluorescent tracer dye, Pacific Blue™, was dissolved in borate buffer and frozen into saline ice projectiles. During acceleration, the ice projectile breaks up in flight into micron‐sized particles that impact the target. Quantitative fluorescence microscopic analysis of the targets demonstrated that under certain impact conditions, 10–50% of the entrained organic molecules were captured in over 25% of the particle impacts. Optimal organic capture was observed for small particles (d ~ 5–15 µm) with velocities ranging from 1 to 2 km s−1. Our results reveal how organic capture efficiency depends on impact velocity and particle size; capture increases as particles get smaller and as velocity is reduced. These results demonstrate the feasibility of collecting unmodified organic molecules from the Enceladus ice plume for sensitive analysis with modern in situ instrumentation such as microfluidic capillary electrophoresis (CE) analysis with ppb organic sensitivity.

^1,2D. Ostrowski,^1,2K. Bryson
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13562]
¹NASA Ames Research Center, Mountain View, California, 94035 USA
²Bay Area Environmental Research Institute, NASA Ames Research Center, Mountain View, California, 94035 USA
Published by arrangement wit John Wiley & Sons

Meteorites provide vast amounts of information on the makeup and history of the solar system. The physical properties help to understand meteor behavior in the atmosphere, model characteristics of parent bodies, and determine methods to deflect potentially hazardous objects. Density and porosity are two of the most important physical properties. All the examined ordinary chondrite falls have bulk densities and porosities near their respected class averages. Most of the studied Antarctic ordinary chondrites have porosities around 12% or higher caused by weathering, placing them near the top of the range of values for chondritic falls. A trend is observed in acoustic velocity, where any meteorite with porosity over 10% has a longitudinal velocity near half the value of the class average. Low porosity meteorites such as Tenham, Chelyabinsk impact melt, and MIL07036 have velocities well above their class averages. Emissivities across all meteorites follow the trend of decreasing emissivity with increasing temperature.

^1,2P.Beck,¹B.Schmitt,¹S.Potin,³A.Pommerol,¹O.Brissaud
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2020.114066]
¹Institut de Planetologie et d’Astrophysique de Grenoble, UGA-CNRS, France
²Institut Universitaire de France, Paris, France
³Physikalisches Institute, Universität Bern, Sidlerstrasse 5, Bern CH-3012, Switzerland
Copyright Elsevier

Generally, the reflectance of a particulate surface depends on the phase angle at which it is observed. This is true for laboratory measurements on powders of natural materials as well as remote observations of Solar System surfaces. Here, we measured the dependences of reflectance spectra with phase angles, of a suite of 72 meteorites in the 400–2600 nm range. The 10–30° phase angle range is investigated in order to study the contribution of Shadow Hiding Opposition Effect (SHOE) to the phase behavior. The behavior is then extrapolated to phase angle of 0° using a polynomial fit, in order to provide grounds for comparison across meteorite groups (enabling to remove the contribution of shadows to reflectance) as well as to provide “equivalent albedo” values that should be comparable to geometric albedo values derived for small bodies. We find a general behavior of increasing strength of the SHOE with lower reflectance values (whether between samples or for a given samples with absorption features). This trend provides a first order way to correct any reflectance spectra of meteorite powders measured under standard conditions (g = 30°) from the contribution of shadows. The g = 0° calculated reflectance and equivalent albedos are then compared to typical values of albedos for main-belt asteroids. This reveals that among carbonaceous chondrites only Tagish Lake group, CI, and CM chondrites have equivalent albedo compatible with C- and D-type asteroids. On the other hand equivalent albedo derived with CO, CR and CK chondrites are compatible with L- and K-type asteroids. The equivalent albedo derived for ordinary chondrites is related to petrographic types, with low-grade petrographic type (type 3.6 and less) being generally darker that higher petrographic types. This works provides a framework for further understanding of the asteroids meteorite linkage in particular when combining with colors and spectroscopy.

¹Kevin Volk,^1,2G. C. Sloan,³Kathleen E. Kraemer
Astrophysics and Space Science 365, 88 Link to Article [DOI
https://doi.org/10.1007/s10509-020-03798-2]
¹Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD, 21218, USA
²Department of Physics and Astronomy, University of North Carolina, Chapel Hill, USA
³Boston College, Institute for Scientific Research, 140 Commonwealth Avenue, Chestnut Hill, MA, 02467, USA

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¹Andreas Morlok,¹Benjamin Schiller,¹Iris Weber,²Mohit Melwani Daswani,¹Aleksandra N.Stojic,¹Maximilian P.Reitze,¹Tim Gramse,³Stephen D.Wolters,¹Harald Hiesinger,³Monica M.Grady,⁴Joern Helbert
Planetary and Space Science (in Press) Link to Article [https://doi.org/10.1016/j.pss.2020.105078]
¹Institut für Planetologie, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Str. 10, 48149, Münster, Germany
²Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr, Pasadena, CA, 91109, USA
³School of Physical Sciences, Open University, Milton Keynes, MK76AA, UK
⁴Institute for Planetary Research, DLR, Rutherfordstrasse 2, 12489, Berlin, Germany

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¹Mason B.Gardner,¹Brent R.Westbrook,¹Ryan C.Fortenberry
Planetary and Space Science (in Press) Link to Article [https://doi.org/10.1016/j.pss.2020.105076]
¹University of Mississippi, Department of Chemistry & Biochemistry, University, MS, 38677, U.S.A

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