¹Yves Marrocchi,²Lydie Bonal,³Jérome Gattacceca,¹Laurette Piani,²Pierre Beck,⁴Richard Greenwood,²Jolantha Eschrig,¹Anne Basque,⁵Pasquale Mario Nuccio,^6,7Franco Foresta Martin
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13552]
¹CRPG, CNRS, Université de Lorraine, UMR 7358, Vandoeuvre‐lès‐Nancy, 54501 France
²Institut de Planétologie et d’Astrophysique de Grenoble, Grenoble, France
³Aix‐Marseille Univ, CNRS, IRD, Coll France, INRAE, CEREGE, Aix‐en‐Provence
⁴PSS, Open University, Walton Hall, Milton Keynes, MK7 6AA UK
⁵Università di Palermo, Palermo, Italy
⁶Instituto Nazionale di Geofisica e Vulcanologia, Sezione di Palermo, 90146 Palermo, Italy
⁷Laboratorio Museo di Scienze della Terra, Ustica, Palermo, Italy
Published by Arrangement with John Wiley & Sons

The Piancaldoli ordinary chondrite fell in northern Italy on August 10, 1968. Preliminary studies led to its classification as an LL3.4 unequilibrated ordinary chondrite. However, recent developments in classification procedures have prompted us to re‐examine its mineralogical, petrographic, spectroscopic, chemical, and isotopic features in a multi‐technique study. Raman spectra and magnetic properties indicate that Piancaldoli experienced minimal thermal metamorphism, consistent with its high bulk hydrogen content and the Cr contents of ferroan olivines in its type II chondrules. In combination with findings of previous studies, our data thus confirm the variability of Cr contents in ferroan olivines in type II chondrules as a proxy of thermal metamorphism. Furthermore, our results reveal that Piancaldoli is less altered than previously reported and should be reclassified as an LL3.10 unequilibrated ordinary chondrite. Our results also imply that the bulk deuterium enrichment, as observed in Piancaldoli (LL3.10), Bishunpur (LL3.15), and Semarkona (LL3.00), is a specific signature of the most primitive unequilibrated ordinary chondrites. Based on our results, we propose that, to date, Piancaldoli is the second least‐altered unequilibrated ordinary chondrite fall after Semarkona. This work reiterates the importance of meteorite collections worldwide as fundamental resources for studying the formation conditions and evolution of our solar system.

¹Paula Lindgren et al. (>10)
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2020.08.021]
¹Department of Geology, Lund University, Sölvegatan 12, 223 62 Lund, Sweden
Copyright Elsevier

The CM carbonaceous chondrites have all been aqueously altered, and some of them were subsequently heated in a parent body environment. Here we have sought to understand the impact of short duration heating on a highly aqueously altered CM through laboratory experiments on Allan Hills (ALH) 83100. Unheated ALH 83100 contains 83 volume per cent serpentine within the fine-grained matrix and altered chondrules. The matrix also hosts grains of calcite and dolomite, which are often intergrown with tochilinite, Fe(Ni) sulphides (pyrrhotite, pentlandite), magnetite and organic matter. Some of the magnetite formed by replacement of Fe(Ni) sulphides that were accreted from the nebula. Laboratory heating to 400 °C has caused partial dehydroxylation of serpentine and loss of isotopically light oxygen leading to an increase in bulk δ¹⁸O and fall in Δ¹⁷O. Tochilinite has decomposed to magnetite, whereas carbonates have remained unaltered. With regards to infrared spectroscopy (4000–400 cm^-1; 2.5 – 25 µm), heating to 400 °C has resulted in decreased emissivity (increased reflectance), a sharper and more symmetric OH band at 3684 cm^-1 (2.71 µm), a broadening of the Si-O stretching band together with movement of its minimum to longer wavenumbers, and a decreasing depth of the Mg-OH band (625 cm^-1; 16 µm). The Si-O bending band is unmodified by mild heating. With heating to 800 °C the serpentine has fully dehydroxylated and recrystallized to ∼Fo_60/70 olivine. Bulk δ¹⁸O has further increased and Δ¹⁷O decreased. Troilite and pyrrhotite have formed, and recrystallization of pentlandite has produced Fe,Ni metal. Calcite and dolomite were calcined at ∼700 °C and in their place is an un-named Ca-Fe oxysulphide. Heating changes the structural order of organic matter so that Raman spectroscopy of carbon in the 800 °C sample shows an increased (D1 + D4) proportional area parameter. The infrared spectrum of the 800 °C sample confirms the abundance of Fe-bearing olivine and is very similar to the spectrum of naturally heated stage IV CM Pecora Escarpment 02010. The temperature-related mineralogical, chemical, isotopic and spectroscopic signatures defined in ALH 83100 will help to track the post-hydration thermal histories of carbonaceous chondrite meteorites, and samples returned from the primitive asteroids Ryugu and Bennu.

^1,2Z.Ren,²P.M.Vasconcelos
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2020.08.019]
¹State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan, 430074, China
²School of Earth and Environmental Sciences, The University of Queensland, Brisbane, Qld 4072, Australia
Copyright Elsevier

Jarosite [KFe₃(SO₄)₂(OH)₆] occurs both as a hydrothermal mineral or as the product of weathering and chemical sedimentation. It has been used in ⁴⁰Ar/³⁹Ar geochronology to date water-rock interaction and weathering processes on the surfaces of Earth and Mars, but the lack of information about Ar diffusivity parameters relevant to specific types of jarosites makes the interpretation of geochronological results tentative. We have filled this gap by investigating Ar diffusion parameters in representative supergene and hypogene jarosites. Detailed diffusion studies were carried out on a hypogene jarosite sample from Gilbert, Nevada, and two supergene jarosite samples from Baiyin, China. The diffusion studies were accompanied by in-situ heating investigations in a transmission electron microscope to directly determine the thermal stability and the phase transformations that jarosite undergoes under progressive heating under ultra-high vacuum. The TEM results suggest that jarosite is stable under vacuum up to ∼ 400 °C, when it undergoes phase transition to yavapaiite [KFe(SO₄)₂] and hematite (Fe₂O₃). Incremental-heating experiments reveal average diffusion parameters of E_a = 138.6 ± 4.2 kJ/mol and ln(D_o/a²) = 9.9 ± 0.9 ln(s^-1) for hypogene jarosite; E_a = 110.3 ± 3.2 kJ/mol and ln(D_o/a²) = 5.7 ± 0.7 ln(s^-1) for one supergene jarosites; and E_a = 141.2 ± 7.9 kJ/mol and ln(D_o/a²) = 11.3 ± 1.7 ln(s^-1) for the other supergene jarosite sample from the same weathering profile. Jarosite closure temperatures depend strongly on sieve size. For samples between 500-200 µm (grain size usually used for samples in Ar geochronology), at a cooling rate 100 °C·Ma^-1, the closure temperatures are 143 ± 18 °C for hypogene and 105 ± 8 and 113 ± 14 °C, respectively, for the two supergene jarosites. Forward modelling of incremental-heating results predicts that coarse-grained hypogene jarosite is retentive of Ar below 50 °C for 100 Ma and below 25 °C for 4 Ga. Densely packed supergene jarosite grains larger than 200 µm are suitable for ⁴⁰Ar/³⁹Ar geochronology at the timescales suitable for investigating water-rock interaction at the surface of Earth and Mars. Fine-grained, porous jarosites require detailed diffusion analyses prior to geochronology due to possible high Ar losses over Ma timescales. The absence of jarosites older than ∼40 Ma on Earth suggests that jarosite may require continuous exposure to acid oxidizing conditions, and that it does not survive burial and exhumation. Therefore, the occurrence of jarosite on Earth and Mars may identify segments of the planets’ surfaces continuously exposure to acid-oxidizing conditions since jarosite precipitation.

¹Justina Novakova,^1,2Monika Jerigova,³Eduard Jane,²Vojtech Szoecs,^1,2DusanVelic
Planetary and Space Sience (in Press) Link to Article [https://doi.org/10.1016/j.pss.2020.105012]
¹Faculty of Natural Sciences, Comenius University, Ilkovičova 6, 842 48, Bratislava, Slovakia
²International Laser Centre, Ilkovičova 3, 842 48, Bratislava, Slovakia
³Institute of Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, 845 38, Bratislava, Slovakia

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

¹Yayoi N.Miura,²Mamoru Okuno,²Yuichiro Cho,^1,2,3Kazuo Yoshiok,²Seiji Sugita
Planetary and Space Science (in Press) Link to Article [https://doi.org/10.1016/j.pss.2020.105046]
¹Earthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo, 113-0032, Japan
²Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo, 113-0033, Japan
³Department of Complexity Science and Engineering, Graduate School of Frontier Sciences, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8561, Japan

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

¹S.T.Port,¹V.F.Chevrier
Planetary and Space Science (in Press) Link to Article [https://doi.org/10.1016/j.pss.2020.105022]
¹University of Arkansas, Center for Space and Planetary Sciences, Fayetteville, AR, 72701, United State

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

¹Jingyi Mah,¹Ramon Brasser
¹Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2020.114052]
¹Earth Life Science Institute, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8550, Japan
Copyright Elsevier

Combining isotopic constraints from meteorite data with dynamical models of planet formation proves to be advantageous in identifying the best model for terrestrial planet formation. Prior studies have shown that the probability of reproducing the distinct isotopic compositions of the Earth and Mars for both classical and Grand Tack models is very low. In the framework of the Grand Tack model, for Mars to be isotopically different from the Earth, it had to form under very specific conditions. Here, we subjected a fairly new and unexplored model—the depleted disc model—to the test. It presupposes that the region in the inner protoplanetary disc from Mars’ orbit and beyond is depleted in mass such that Mars is left with insufficient material to grow to a larger size. Our aim is to test the whether the distinct isotopic compositions of the Earth and Mars are a natural outcome of this model. We found that the terrestrial planets accrete material mostly locally and have feeding zones that are sufficiently distinct. The Earth and Mars, and by extension, Venus, can have distinct isotopic compositions if there is an isotopic gradient in the terrestrial planet region of the protoplanetary disc. Our results suggest that the material in the inner Solar System most likely did not undergo substantial mixing that homogenised the potential isotopic gradient, in contrast to the Grand Tack model where the feeding zones of the terrestrial planets are nearly identical due to the mixing of material by Jupiter’s migration.

¹Daniel P.Glavin et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13560]
¹NASA Goddard Space Flight Center, Greenbelt, Maryland, 20771 USA
Published by arrangement with John Wiley & Sons

The Asuka (A)‐12236 meteorite has recently been classified as a CM carbonaceous chondrite of petrologic type 3.0/2.9 and is among the most primitive CM meteorites studied to date. Here, we report the concentrations, relative distributions, and enantiomeric ratios of amino acids in water extracts of the A‐12236 meteorite and another primitive CM chondrite Elephant Moraine (EET) 96029 (CM2.7) determined by ultra‐high‐performance liquid chromatography time‐of‐flight mass spectrometry. EET 96029 was highly depleted in amino acids and dominated by glycine, while a wide diversity of two‐ to six‐carbon aliphatic primary amino acids were identified in A‐12236, which had a total amino acid abundance of 360 ± 18 nmol g−1, with most amino acids present without hydrolysis (free). The amino acid concentrations of A‐12236 were double those previously measured in the CM2.7 Paris meteorite, consistent with A‐12236 being a highly primitive and unheated CM chondrite. The high relative abundance of α‐amino acids in A‐12236 is consistent with formation by a Strecker‐cyanohydrin dominated synthesis during a limited early aqueous alteration phase on the CM meteorite parent body. The presence of predominantly free glycine, a near racemic mixture of alanine (d/l ~0.93–0.96), and elevated abundances of several terrestrially rare non‐protein amino acids including α‐aminoisobutyric acid (α‐AIB) and racemic isovaline indicate that these amino acids in A‐12236 are extraterrestrial in origin. Given a lack of evidence for biological amino acid contamination in A‐12236, it is possible that some of the l‐enantiomeric excesses (lee ~34–64%) of the protein amino acids, aspartic and glutamic acids and serine, are indigenous to the meteorite; however, isotopic measurements are needed for confirmation. In contrast to more aqueously altered CMs of petrologic types ≤2.5, no l‐isovaline excesses were detected in A‐12236. This observation strengthens the hypothesis that extensive parent body aqueous activity is required to produce or amplify the large l‐isovaline excesses that cannot be explained solely by exposure to circularly polarized radiation or other chiral symmetry breaking mechanisms prior to incorporation into the asteroid parent body.

¹Jan L.Hellmann,^1,2Timo Hopp,¹Christoph Burkhardt,¹ThorstenKleine
Earth and Planetary Science Letters 549, 116508 Link to Article [https://doi.org/10.1016/j.epsl.2020.116508]
¹Institut für Planetologie, University of Münster, Wilhelm-Klemm-Straße 10, 48149 Münster, Germany
²Origins Laboratory, Department of the Geophysical Sciences and Enrico Fermi Institute, The University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60637, USA
Copyright Elsevier

Compared to the composition of CI chondrites and the Sun, all other carbonaceous chondrites are variably depleted in volatile elements. However, the origin of these depletions, and how they are related to volatile loss during high-temperature processes within the solar nebula, are unclear. To better understand the processes that caused volatile element fractionations among carbonaceous chondrites, we obtained mass-dependent Te isotopic compositions and Te concentrations for a comprehensive set of samples from the major carbonaceous chondrite groups. The chondrites exhibit well-resolved inter-group Te isotope variations towards lighter isotopic compositions for increasingly volatile-depleted samples. The Te isotopic compositions and concentrations are also correlated with the mass fraction of matrix and with nucleosynthetic Cr anomalies. Combined, these correlations indicate mixing between volatile-rich, isotopically heavy, and ⁵⁴Cr-rich CI-like matrix with volatile-poor, isotopically light, and ⁵⁴Cr-poorer chondrules or chondrule precursors. The Te-Cr isotopic correlation suggests that all carbonaceous chondrites contain CI-like matrix, and that chondrules and this CI-like matrix formed from isotopically distinct material originating from different regions of the disk. The only samples plotting off the Te-Cr correlation are CR chondrites, indicating that CR chondrules formed from different precursor material than chondrules from other carbonaceous chondrites, either because they formed at greater heliocentric distance and/or at a later time. Plots of volatile element abundances versus matrix mass fraction reveal that chondrules/chondrule precursors display CI-chondritic ratios for volatile elements with 50% condensation temperatures below ∼750 K, with an overall abundance of ∼0.13 × CI. Mixing between these two components, therefore, naturally results in CI-like ratios for these elements in all carbonaceous chondrites, in spite of different degrees of volatile depletion. A corollary of this observation is that the CI-like ratios of volatile elements in the bulk silicate Earth may result from the accretion of volatile-depleted materials and do not require accretion of CI chondrites themselves.

¹Shirai, N.,¹Hozumi, T.,²Toh, Y.,^1,3Ebihara, M.
Journal of Radioanalytical and Nuclear Chemistry (in Press) Link to Article [DOI: 10.1007/s10967-020-07273-8]
¹Department of Chemistry, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo 192-0397, Japan
²Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Shirakata, Tokai-mura, Ibaraki 319-1195, Japan
³Department of Earth Sciences, Waseda University, 1-6-1 Nishi-Waseda, Shinjuku-ku, Tokyo, 169-8050, Japan

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