¹Kim V. Fendrich,¹Denton S. Ebel
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13623]
¹Department of Earth and Planetary Sciences, American Museum of Natural History, New York, New York, 10024 USA
Published by arrangement with John Wiley & Sons

The size, distribution, abundance, and physical and chemical characteristics of chondritic inclusions are key features that define the chondrite groups. We present statistics on the size and abundance of the macroscopic components (inclusions) in the Murchison (CM2) and Allende (CV3) chondrites and measure their general chemical trends using established X‐ray mapping techniques. This study provides a fine‐scale assessment of the two meteorites and a semiquantitative evaluation of the relative abundances of elements and their distribution among meteorite components. Murchison contains 72% matrix and 28% inclusions; Allende contains 57% and 43%, respectively. A broad range of inclusion sizes and relative abundances has been reported for these meteorites, which demonstrates the necessity for a more standardized approach to measuring these characteristics. Nonetheless, the characteristic mean sizes of inclusions in Allende are consistently larger than those in Murchison. We draw two significant conclusions (1) these two meteorites sampled distinct populations of chondrules and refractory inclusions, and (2) complementary Mg/Si ratios between chondrules and matrix are observed in both Murchison and Allende. Both support the idea that chondrules and matrix within each chondrite group originated in single reservoirs of precursors with approximately solar Mg/Si ratios, providing a constraint on astrophysical models of the origin of chondrite parent bodies.

^1,3Xiandi Zeng,^1,2,4Hong Tang,^1,2,4Xiong Yao Li,¹Xiaoji Zeng,^1,2,4Wen Yu,^1,2,4Jianzhong Liu,⁵Yongliao Zou
Earth and Planetary Science Letters Link to Article [https://doi.org/10.1016/j.epsl.2021.116806]
¹Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
²CAS Center for Excellence in Comparative Planetology, Hefei, China
³University of Chinese Academy of Sciences, Beijing 100049, China
⁴Key Laboratory of Space Manufacturing Technology, Chinese Academy of Sciences, Beijing 100094, China
⁵National Space Science Center, Chinese Academy of Sciences, Beijing 100190, China
Copyright Elsevier

Determining the characteristics and thermal stability of solar wind-produced OH/H2O is critical to understanding the formation and migration of water on the lunar surface. In this study, terrestrial plagioclase (An50−53) was used as a lunar analogue and was irradiated with 5 keV H+ at a fluence of ∼1×1017 H+/cm2. The irradiated plagioclase was characterized via Fourier transform infrared spectroscopy, nanoscale secondary ion mass spectrometry, Raman spectroscopy, and transmission electron microscopy. The thermal stability of OH/H2O in the irradiated plagioclase was investigated via heating experiments. Our results reveal (1) a ∼100–200 ppm increase in the water content of the irradiated plagioclase; (2) structural hydrous species formation in the plagioclase through H+ implantation, including Type I H2O (∼2.75 μm) and Type II H2O (∼2.90 μm); and (3) the escape of much of the OH/H2O formed by H+ implantation at a temperature equivalent to the highest temperature on the lunar surface. The results of this study can improve our understanding of OH/H2O thermal stability on the lunar surface and provide a baseline for the interpretation of remote sensing observations.

¹J.Rojas,^2,1J.Duprat,¹C.Engrand,³E.Dartois,¹L.Delauche,^1,3M.Godard,²M.Gounelle,^4,5J.D.Carrillo-Sánchez,^4,6P.Pokorný,⁷J.M.C.Plane
Earth and Planetary Science Letters 560, 116794 Link to Article [https://doi.org/10.1016/j.epsl.2021.116794]
¹Université Paris-Saclay, CNRS/IN2P3, IJCLab, 91405 Orsay, France
²IMPMC, CNRS-MNHN-Sorbonne Universités, UMR7590, 57 rue Cuvier, 75005 Paris, France
³ISMO, CNRS, Univ. Paris Saclay, Bât 520, 91405 Orsay, France
⁴Department of Physics, Catholic University of America, 620 Michigan Ave., N.E. Washington, DC 20064, USA
⁵ITM Physics Laboratory, NASA Goddard Space Flight Center, Code 675, 8800 Greenbelt Rd., Greenbelt, MD 20771, USA
⁶Astrophysics Science Division, NASA Goddard Space Flight Center, Code 667, 8800 Greenbelt Rd., Greenbelt, MD, USA
⁷School of Chemistry, Univ. of Leeds, Leeds LS2 9JT, UK
Copyright Elsevier

The annual flux of extraterrestrial material on Earth is largely dominated by sub-millimetre particles. The mass distribution and absolute value of this cosmic dust flux at the Earth’s surface is however still uncertain due to the difficulty in monitoring both the collection efficiency and the exposure parameter (i.e. the area-time product in m2.yr). In this paper, we present results from micrometeorite collections originating from the vicinity of the CONCORDIA Station located at Dome C (Antarctica), where we performed several independent melts of large volumes of ultra-clean snow. The regular precipitation rate and the exceptional cleanliness of the snow from central Antarctica allow a unique control on both the exposure parameter and the collection efficiency. A total of 1280 unmelted micrometeorites (uMMs) and 808 cosmic spherules (CSs) with diameters ranging from 30 to 350 μm were identified. Within that size range, we measured mass fluxes of 3.0 μg.m−2.yr−1 for uMMs and 5.6 μg.m−2.yr−1 for CSs. Extrapolated to the global flux of particles in the 12-700 μm diameter range, the mass flux of dust at Earth’s surface is tons.yr−1 ( and tons.yr−1 of uMMs and CSs, respectively). We indicate the statistical uncertainties expected for collections with exposure parameters in the range of 0.1 up to 105 m2.yr. In addition, we estimated the flux of altered and unaltered carbon carried by heated and un-heated particles at Earth’s surface. The mass distributions of CSs and uMMs larger than 100 μm are fairly well reproduced by the CABMOD-ZoDy model that includes melting and evaporation during atmospheric entry of the interplanetary dust flux. These numerical simulations suggest that most of the uMMs and CSs originate from Jupiter family comets and a minor part from the main asteroid belt. The total dust mass input before atmospheric entry is estimated at 15,000 tons.yr−1. The existing discrepancy between the flux data and the model for uMMs below 100 μm suggests that small fragile uMMs may evade present day collections, and/or that the amount of small interplanetary particles at 1 AU may be smaller than expected.

^1,2,3E.Tatsumi et al. (>10)
Nature Astronomy 5, 39–45 Link to Article [DOI https://doi.org/10.1038/s41550-020-1179-z]
¹Instituto de Astrofísica de Canarias (IAC), University of La Laguna, La Laguna, Spain
²Department of Astrophysics, University of La Laguna, La Laguna, Spain
³The University of Tokyo, Tokyo, Japan

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

¹Alexey Potapov,²Jeroen Bouwman,¹Cornelia Jäger,²Thomas Henning
Nature Astronomy 5, 78–85 Link to Article [DOI https://doi.org/10.1038/s41550-020-01214-x]
¹Laboratory Astrophysics Group of the Max Planck Institute for Astronomy at the Friedrich Schiller University Jena, Institute of Solid State Physics, Jena, Germany
²Max Planck Institute for Astronomy, Heidelberg, Germany

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

^1,2D. N. DellaGiustina et al. (>10)
Nature Astronomy 5, 31–38 Link to Article [DOI https://doi.org/10.1038/s41550-020-1195-z]
¹Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
²Department of Geosciences, University of Arizona, Tucson, AZ, USA

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

¹Jiří Borovička,²Felix Bettonvil,³Gerd Baumgarten,⁴Jörg Strunk,⁵Mike Hankey,¹Pavel Spurný,⁶Dieter Heinlein
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13628]
¹Astronomical Institute of the Czech Academy of Sciences, Fričova 298, CZ‐25165 Ondřejov, Czech Republic
²Leiden Observatory, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, the Netherlands
³Leibniz‐Institute of Atmospheric Physics at Rostock University, Schlossstraße 6, D‐18225 Kühlungsborn, Germany
⁴European Fireball Network and Arbeitskreis Meteore, D‐32049 Herford, Germany
⁵American Meteor Society LTD, 54 Westview Crescent, Geneseo, New York, 14454 USA
⁶German Fireball Network, Lilienstraße 3, D‐86156 Augsburg, Germany
Published by arrangement with John Wiley & Sons

The C1‐ungrouped carbonaceous chondrite Flensburg fell in Germany on September 12, 2019, in the daytime. We determined the atmospheric trajectory, velocity, and heliocentric orbit using one dedicated AllSky6 meteor camera and three casual video records of the bolide. It was found that the meteorite originated in the vicinity of the 5:2 resonance with Jupiter at heliocentric distance of 2.82 AU. When combined with the bolide energy reported by the United States government sensors (USGS), the preatmospheric diameter of the meteoroid was estimated to be 2–3 m and the mass to be 10,000–20,000 kg. The meteoroid fragmented heavily in the atmosphere at heights of 46–37 km, under dynamic pressures of 0.7–2 MPa. The recovery of just one meteorite suggests that only a very small part of the original mass reached the ground. The bolide velocity vector was compared with that reported by the USGS. There is good agreement in the radiant but the velocity value has been underestimated by the USGS by almost 1 km s−1.

¹Morlok, Andreas et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114363]
¹Institut für Planetologie, Westfälische Wilhelms-Universität Universität Münster, Wilhelm-Klemm-Strasse 10, 48149, Germany
Copyright Elsevier

We have synthesized and analyzed silicate glasses that are representative for the glasses on the surface of Mercury by mid-infrared reflectance spectroscopy, based on high-pressure laboratory experiments and the resulting compositions of the glass phase. The spectra are of interest for investigating the surface of Mercury using the MERTIS (Mercury Radiometer and Thermal Infrared Spectrometer) instrument on board of the ESA/JAXA BepiColombo mission.

Both powdered fractions and polished blocks have been analyzed. Powdered size fractions of 0–25 μm, 25-63 μm, 63-125 μm, and 125–250 μm were measured in reflectance in the thermal infrared (2–20 μm). Spectra for powdered bulk glasses (1.6 wt% – 19.0 wt% MgO) show a single, dominating Reststrahlenband (RB, 9.3–9.8 μm), a Christiansen Feature (CF; 7.6 μm – 8.1 μm), and a size dependent Transparency Feature (TF; 11.6–11.9 μm). Micro-FTIR analyses of polished blocks of glasses (3.4–26.5 wt% MgO) have characteristic bands at 7.8–8.2 μm (CF), and 9.3–9.9 μm (RB). Only few olivine crystalline features were observed.

Spectral features correlate with compositional characteristics, e.g. SiO2 content or SCFM (SiO2/(SiO2 + CaO + FeO + MgO) index. The strongest correlation between band features CF and the strong RB are with Mg/Si. No simple mixture of glass spectra from this study is able to reproduce the entire ground based spectrum of the surface of Mercury. However Mg-rich glasses reproduce identified features at 8.5 μm, 9.9 μm and 12.4 μm.

¹Yuuya Nagaashi,¹Takanobu Aoki,¹Akiko M.Nakamura
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114357]
¹Graduate School of Science, Kobe University, 1-1 Rokkodaicho, Nada-ku, Kobe 657-8501, Japan
Copyright Elsevier

The cohesion of particles has a significant effect on the properties of small bodies. In this study, we measured in open air, the cohesive forces of tens of micron-sized irregularly shaped meteorite, silica sand, glass powder, and spherical glass particles, using a centrifugal method. In addition, we estimated the amount of water vapor adsorbed on the particles under the measurement conditions. The measured cohesive forces of the meteorite particles are tens of times smaller than those of an ideally spherical silica particle and correspond to the submicron-scale effective (or equivalent) curvature radius of the particle surface. Moreover, based on the estimated amount of water vapor adsorbed on the particles, we expect the cohesive forces of the particles in airless bodies to be approximately 10 times larger than those measured in open air. Based on the measurement results, we estimate that the cohesive forces of the particles on asteroids are typically in the sub-micro-Newton range, and that the particles on fast-rotating asteroids are tens of microns in size.

¹Gordon M.Gartrelle,²Paul S.Hardersen,³Matthew R.M.Izawa,⁴Matthew C.Nowinski
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114349]
¹University of North Dakota, Grand Forks, ND, USA
²Trouvaille LLC, Tucson, AZ, USA
³Institute for Planetary Materials, Okayama University, Misasa, Japan
⁴George Mason University, Fairfax, VA, USA
Copyright Elsevier

Asteroids are the origin point for most meteorites impacting Earth. Terrestrial meteorite samples provide evidence of what actually occurred in the early solar system at the formation location of the meteorite, and when it occurred. The ability to connect a meteorite sample to an asteroid parent body provides its starting location as a meteoroid. To date, only a handful of chondritic meteorite types have been credibly connected to an asteroid parent. For the past two decades, D-type asteroids, a dark, spectrally reddish, and featureless taxonomic type have been speculated to be the parent body of the tiny family of ungrouped chondrites. These include the Tagish Lake Meteorite (TLM), a ~ 4 m meteorite “fall” in Canada’s Yukon territory recovered in 2000. The quest to identify the TLM parent has been a baffling one as D-type asteroids are dominant among the Jovian Trojans, rare in main asteroid belt, and extremely rare in the inner asteroid belt as well as Near-Earth space.

This study employed Near Infrared (NIR) spectra (0.7–2.45 μm) of 86 D-types and a variety of analysis techniques including visual analysis, slope analysis, curve fitting, Fréchet analysis, dynamical analysis and Shkuratov radiative transfer theory to search for the TLM parent body. Sixteen TLM samples from the NASA Reflectance Experiment Laboratory (RELAB) plus five additional mineralogically well-constrained samples measured using X-ray diffraction (XRD) and Rietveld refinement were compared to D-type asteroid spectra. Our results indicate, out of several promising candidates, Near-Earth asteroid 17274 (2006 LC16), a ~ 3 km diameter Amor asteroid is a plausible parent body for TLM.