¹Sergei Batovrin,¹Boris Lipovsky,²Yury Gulbin,³Yury Pushkarev,³Yury A. Shukolyukov
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13662]
¹Independent Researcher, 120 Casals Place, Bronx, New York, 10475 USA
²The Mining Institute of St. Petersburg, Vasilevsky ostrov, 21 Liniya, Dom 2, St. Petersburg, 199106 Russia
³Institute of Geology and Geochronology of Precambrian, RAS, Naberezhnaya Makarova 2, St. Petersburg, 199034 Russia
Published by arrangement with John Wiley & Sons

Terrestrially occurring iron silicide spherules, described in the geological literature for 160 years as cosmogenic and approved as “extraterrestrial” minerals by IMA CNMMN in 1984, so far have escaped any serious examination by meteoriticists. Our isotopic and REE data, obtained for silicide spherules for the first time, disagree with the meteoritic origin of gupeiite (Fe3Si) and xifengite (Fe5Si3) spherules from two continents. Despite departures from terrestrial norms (87Rb/86Sr—0.0174; 87Sr/86Sr—0.700181; 3He/4He—7.57 × 10−6; 40Ar/36Ar—325.9), the compositions of 143Nd/144Nd (0.512034) and 147Sm/144Nd (0.06357), as well as REE abundances, clarify provenance from upper crust sediments for samples with U/Pb age of 121–314 ka from the Ala-Tau range in the Urals. However, the morphology of flanged button shapes, ring waves, and eccentro-radiating ridges reliably constrains the origin of silicide spherules to distal meteoritic impact ejecta. Arc jet ablation experiments have previously demonstrated that similar morphologies, observed on australite tektites, reflect aerodynamic ablation rates corresponding to flight velocities well into orbital range. These features are generally accepted as conclusive evidence for hypervelocity atmospheric entry from space. Internal structure, consistent with accretion through the coalescence of 3–5 µm droplets, and composition, closely corresponding to 1893–1154 K span of C-type condensation sequences, indicate a high probability of processing through recondensation of ejecta vapor.

¹Yoko Kebukawa et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13713]
¹Department of Chemistry and Life Science, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama, 240-8501 Japan
Published by arrangement with John Wiley & Sons

The Almahata Sitta (AhS) meteorite is a unique polymict ureilite. Recently, carbonaceous chondritic lithologies were identified in AhS. Organic matter (OM) is ubiquitously found in primitive carbonaceous chondrites. The molecular and isotopic characteristics of this OM reflect its origin and parent body processes, and are particularly sensitive to heating. The C1 lithologies AhS 671 and AhS 91A were investigated, focusing mainly on the OM. We found that the OM in these lithologies is unique and contains primitive isotopic signatures, but experienced slight heating possibly by short-term heating event(s). These characteristics support the idea that one or more carbonaceous chondritic bodies were incorporated into the ureilitic parent body. The uniqueness of the OM in the AhS samples implies that there were large variations in primitive carbonaceous chondritic materials in the solar system other than known primitive carbonaceous chondrite groups such as CI, CM, and CR chondrites.

¹Mehmet Yesiltas,²Timothy D. Glotch,³Bogdan Sava
Scientific Reports 11, 11656 Link to Article [DOI https://doi.org/10.1038/s41598-021-91200-8]
¹Faculty of Aeronautics and Space Sciences, Kirklareli University, Kirklareli, Turkey
²Department of Geosciences, Stony Brook University, Stony Brook, NY, USA
³Neaspec GmbH, 85540, Haar, Munich, Germany

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^1,2Claire I. O. Nichols,²James F.J. Bryson,³Rory D. Cottrell,⁴Roger R. Fu,¹Richard J. Harrison,^5,6Julia Herrero-Albillos,⁷Florian Kronast,³John A. Tarduno,⁴Benjamin P. Weiss
Journal of Geophysical Research, Planets (in Press) Link to Article [https://doi.org/10.1029/2021JE006900]
¹Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Insitute of Technology, Cambridge, MA, 02139 USA
²Department of Earth Sciences, University of Oxford, Oxford, OX1 3AN UK
³Department of Earth and Environmental Sciences, University of Rochester, NY, 14627 USA
⁴Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA
⁵Centro Universitario de la Defensa, Carretera de Huesca s/n, E-50090 Zaragoza, Spain
⁶Instituto de Nanociencia y Materiales de Aragón (INMA), CSIC—Universidad de Zaragoza, Zaragoza, 50009 Spain
⁷Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, 12489 Berlin, Germany
Copyright Elsevier

Several paleomagnetic studies have been conducted on five main group pallasites: Brenham, Marjalahti, Springwater, Imilac and Esquel. These pallasites have distinct cooling histories, meaning that their paleomagnetic records may have been acquired at different times during the thermal evolution of their parent body. Here we compile new and existing data to present the most complete time-resolved paleomagnetic record for a planetesimal, which includes a period of quiescence prior to core solidification as well as dynamo activity generated by compositional convection during core solidification. We present new paleomagnetic data for the Springwater pallasite, which constrains the timing of core solidification. Our results suggest that in order to generate the observed strong paleointensities ( ∼ 65 – 95 μT), the pallasites must have been relatively close to the dynamo source. Our thermal and dynamo models predict that the main group pallasites originate from a planetesimal with a large core (> 200 km) and a thin mantle (< 70 km).

¹M.Grott et al. (>10)
Journal of Geophysical Research, Planets (in Press) Link to Article [https://doi.org/10.1029/2021JE006861]
¹German Aerospace Center (DLR), Institute of Planetary Research, Berlin, Germany
Published by arrangment with John Wiley & Sons

The heat flow and physical properties package (HP³) of the InSight Mars mission is an instrument package designed to determine the martian planetary heat flow. To this end, the package was designed to emplace sensors into the martian subsurface and measure the thermal conductivity as well as the geothermal gradient in the 0-5 m depth range. After emplacing the probe to a tip depth of 0.37 m, a first reliable measurement of the average soil thermal conductivity in the 0.03 to 0.37 m depth range was performed. Using the HP³ mole as a modified line heat source, we determined a soil thermal conductivity of 0.039 ± 0.002 W m⁻¹ K⁻¹, consistent with the results of orbital and in-situ thermal inertia estimates. This low thermal conductivity implies that 85 to 95 % of all particles are smaller than 104-173 μm and suggests that soil cementation is minimal, contrary to the considerable degree of cementation suggested by image data. Rather, cementing agents like salts could be distributed in the form of grain coatings instead. Soil densities compatible with the measurements are  kg m⁻³, indicating soil porosities of  %.

¹G.Alemanno,¹A.Maturilli,¹M.D’Amore,¹J.Helbert
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114622]
¹Institute for Planetary Research, German Aerospace Center DLR, Rutherfordstr. 2, 12489 Berlin, Germany
Copyright Elsevier

New spectral orbital thermal infrared data of Mars are being acquired by the thermal infrared channel TIRVIM (in honor of Vassily Ivanovich Moroz) of the Atmospheric Chemistry Suite (ACS) of spectrometers on board of ExoMars2016 mission. TIRVIM encompasses the spectral range of 1.7–17 μm. A major challenge brought by the analysis of these data of planetary bodies with atmospheres is the ability to extract from the data the relevant information about the surface. Thus, laboratory work plays an essential role, providing end-member and mixture spectral data of planetary analogs to fit the orbital data by means of deconvolution techniques. At the Planetary Spectroscopy Laboratory (PSL) of the German Aerospace Center (DLR), we are performing new laboratory experiments on Martian analogs in order to provide a new and updated library of spectra optimized for the interpretation of TIRVIM data. Emissivity measurements, recorded at increasing temperatures, are coupled with reflectance measurements on fresh and thermally processed samples acquired between 1.7 and 17 μm. Building on measurements previously collected on Martian analogues, we have paid particular attention to the study of the spectral behaviour of mixtures of carbonates and phyllosilicates. The main goal of this analysis is to study the variation of the main carbonate spectral features in mixtures with a phyllosilicate component, an important factor for understanding the story of carbonates detections on planetary surfaces and to provide insights for new detections. The results obtained in this work show that the presence of a phyllosilicate component affect the appearance of the carbonate spectral features in the spectral range studied, with a stronger effect in the range between 1.7 and 5 μm. Effects of mineral type and particle size are also investigated and shown to strongly affect the spectral behaviour of laboratory samples. Finally, deconvolution techniques of laboratory emissivity spectra are studied in preparation for the interpretation of atmospherically corrected TIRVIM spectral data, showing that modelled mixtures spectra represent an acceptable reproduction of laboratory spectra of mixtures.

^1,2M. Kimura,³R. C. Greenwood,⁴M. Komatsu,¹N. Imae,¹A. Yamaguchi,²R. Sato
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13704]
¹National Institute of Polar Research, Tokyo, 190-8518 Japan
²Ibaraki University, Mito, 310-8512 Japan
³The Open University, Milton Keynes, MK7 6AA UK
⁴SOKENDAI, Hayama, Kanagawa, 240-0193 Japan
Published by arrangement with John Wiley & Sons

Most carbonaceous (C) chondrites are classified into eight major groups: CI, CM, CO, CV, CK, CR, CH, and CB. However, some are ungrouped. We studied two such chondrites, Asuka (A)-9003 and A 09535. The abundance of chondrules and matrix and chondrule sizes in these meteorites are similar to those in ordinary chondrites and unlike any known carbonaceous chondrite group. In contrast, they contain 4–6 vol% of refractory inclusions and have oxygen isotopic compositions within the range of CO and CV chondrites. Therefore, A-9003 and A 09535 are classified as C chondrites. Petrologic subtypes of A-9003 and A 09535 are 3.2. All these features closely resemble those of another ungrouped chondrite, Yamato (Y)-82094, and differ from those of any C chondrites reported by now. A-9003, A 09535, and Y-82094 likely represent a new type of C chondrite. We provisionally call them CA chondrite after Asuka in Antarctica. Our study suggests a wider range of formation conditions for C chondrites than currently recorded by the major C chondrite groups.

¹Jérôme Gattacceca,¹Pierre Rochette,¹Yoann Quesnel,²Sounthone Singsoupho
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13703]
¹CNRS, Aix-Marseille Univ, IRD, INRAE, Aix-en-Provence, France
²Department of Physics, Faculty of Natural Sciences, National University of Laos, Vientiane, Laos
Published by arrangement with John Wiley & Sons

Among Australasian tektites, the so-called Muong Nong tektites stand out for their peculiar layering and blocky aspect. Although the source crater for the Australasian tektites is not known, Muong Nong tektites are generally considered as a relatively proximal ejecta. The mechanism responsible for the formation of the layering has been a matter of debate. In this work, we revisit the paleomagnetism of Muong Nong tektites. They retain a thermoremanent magnetization acquired during cooling below 585 °C in the presence of the ambient geomagnetic field, and carried magnetite in most samples, although at least one sample containing metallic iron was detected. The inclination of the paleomagnetic direction with respect to the layering plane clusters around 18 ± 12°, compatible with the inclination of the geomagnetic field for this latitude at the time of impact. This indicates that the layering of the Muong Nong tektites was subhorizontal while they were cooling below 585 °C. The preferred scenario for the formation of the layering of layered tektite is therefore by horizontal shear in pools or sheets of molten material.

¹O. Pravdivtseva,²M. E. Varela,¹A. Meshik,³A. J. Campbell,²M. Saavedra,⁴D. Topa
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13708]
¹Laboratory for Space Sciences and Physics Department, Washington University, CB1105, Saint Louis, Missouri, 63130 USA
²ICATE (CONICET-UNSJ), Avenida España 1512 sur, San Juan, J5402DSP Argentina
³Department of the Geophysical Sciences, University of Chicago, 5734 S. Ellis Ave., Chicago, Illinois, 60637 USA
⁴Central Research Laboratories, Natural History Museum, Burgring 7, Vienna, 1010 Austria
Published by arrangement with John Wiley & Sons

The petrographic study of the San Juan A2 polished section demonstrated textural and compositional similarities with the Campo del Cielo IAB iron meteorite, with trace element abundances in metal following the pattern of bulk Campo del Cielo. Xenon, neon, and helium isotopic compositions have been measured in radial graphite rims, massive graphite inclusions, fine-grained graphite aggregates, cliftonite, and platy graphite. Two silicate inclusions and two areas of metal were also analyzed. ³He/⁴He versus ⁴He/²¹Ne data for San Juan metal plot next to the values reported for the El Taco fragment of Campo del Cielo, supporting San Juan being a part of the Campo del Cielo meteorite shower. Based on the Ne isotopic composition of its components, and the observed correlation between ¹²⁸Xe and ¹²⁹Xe, the San Juan A fragment of Campo del Cielo was well shielded from the primary galactic cosmic ray high-energy irradiation. Its size allowed the secondary neutrons to be fairly well thermalized, receiving an equivalent (normalized to the research reactor with highly thermalized neutron spectrum) fluence of thermal and epithermal neutrons of 6.6 × 10¹⁷ n cm⁻². Considering 1.8 × 10⁸ years single-stage and constant exposure geometry irradiation history for Campo del Cielo, and assuming the identical neutron flux spectra for the research reactor and Campo del Cielo, the average thermal equivalent neutron flux for San Juan is about 1.2 × 10² n cm⁻² s⁻¹. Xe isotopic composition in the radial graphite rims and platy graphite shows evidence of live ¹²⁹I in San Juan and is consistent with a mixture of iodine-derived and tellurium-derived Xe.

¹Nisha K. Ramkissoon,¹Stuart M. R. Turner,¹Michael C. Macey,¹Susanne P. Schwenzer,²Mark H. Reed,¹Victoria K. Pearson,¹Karen Olsson-Francis
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13697]
¹AstrobiologyOU, STEM, The Open University, Walton Hall, Milton Keynes, MK7 6AA UK
²Earth Sciences Department, University of Oregon, Eugene, Oregon, 97403–1272 USA
Published by arrangement with John Wiley & Sons

Hydrothermal systems that formed as a result of impact events possess all the key requirements for life: liquid water, a supply of bio-essential elements, and potential energy sources. Therefore, they are prime locations in the search for life on other planets. Here, we apply thermochemical modeling to determine secondary mineral formation within an impact-generated hydrothermal system, using geochemical data returned for two soils on Mars found in regions that have previously experienced alteration. The computed mineral reaction pathways provide a basis for Gibbs energy calculations that enable both the identification of available geochemical energy, obtained from Fe-based redox reactions, that could be utilized by potential microbial life within these environments, and an estimate of potential cell numbers. Our results suggest that water–rock interactions occurring within impact-generated hydrothermal systems could support a range of Fe-based redox reactions. The geochemical energy produced from these reactions would be substantial and indicates that crater environments have the potential to support microbial cell numbers similar to what has been identified in terrestrial environments.