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.

¹GianfrancoDi Vincenzo,^2,3Luigi Folco,^2,4Martin D.Suttle,⁵Lauren Brase,⁵Ralph P.Harvey
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2021.01.046]
¹Istituto di Geoscienze e Georisorse – CNR, via Moruzzi 1, 56124 Pisa, Italy
²Dipartimento di Scienze della Terra, Università di Pisa, Via S. Maria 53, 56126 Pisa, Italy
³CISUP, Centro per l’Integrazione della Strumentazione Scientifica dell’Università di Pisa, Lungarno Pacinotti 42, 56126 Pisa, Italy
⁴Planetary Materials Group, Department of Earth Sciences, Natural History Museum, Cromwell Road, London, SW7 5BD, United Kingdom
⁵Department of Earth, Environmental and Planetary Sciences, Case Western Reserve University, 112 A.W. Smith Bldg., Cleveland, OH 44106-7216, United States
Copyright Elsevier

Microtektites represent high-velocity/distal meteorite impact ejecta. Demonstrating that microtektites found at several locations throughout East-Antarctica consist of a homogeneous class of geological objects belonging to the Australasian tektite/microtektite strewn field is fundamental to define the actual extent of the largest and youngest known tektite field on Earth produced by an asteroidal impact ∼0.8 Ma ago. This study presents new 40Ar/39Ar analyses performed by multi-collector noble gas mass spectrometry on individual microtektites from two key locations in the Transantarctic Mountains: Miller Butte, in northern Victoria Land, and Mount Raymond, over 1,000 km further south, in the Grosvenor Mountains. Results indicate that particles are heavily contaminated by at least one extraneous Ar component, which is not correlated with size nor with bulk chemical composition, and precludes a straightforward interpretation of 40Ar/39Ar data. Analysis of data from step-heating and total fusion analyses in three-isotope correlation diagrams yielded indistinguishable isochron ages from the two locations, with a combined isochron average of 800±89 ka (95% confidence level). These age results improve by more than one order of magnitude previously published 40Ar/39Ar age determinations and improve by ∼4 times a previous fission track date, thus providing conclusive evidence that microtektites found throughout the Transantarctic Mountains of Antarctica belong to a single source – the Australasian field. This study strengthens the southward extension of the Australasian field (∼4,000 km southward with respect to Australasian microtektites recovered at lower latitudes from deep sea sediments), thus implying a launch distance of nearly 12,000 km from the putative impact location in Indochina. From a broad perspective, results also reveal a contrasting behavior between microtektites from the Transantarctic Mountains, highly contaminated by extraneous Ar, and Australasian macroscopic tektites, weakly or negligibly contaminated. Although future dedicated experimental work, aimed at the definition of physical homogeneity of microtektites at the submicroscale and at the understanding of the true intra-particle spatial distribution of Ar isotopes are necessary, we speculatively hypothesize that the contrasting behavior between tektites and microtektites may reflect displacement in different environments.

^1,2,3Kirtland J.Robinson,²Christiana Bockisch,²Ian R.Gould,⁴Yiju Liao,⁴Ziming Yang,⁵Christopher R.Glein,²Garrett D.Shaver,^2,3Hilairy E.Hartnett,³Lynda B.Williams,^2,3Everett L.Shock
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2021.01.038]
¹Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, 02543
²School of Molecular Sciences, Arizona State University, Tempe, Arizona, 85287
³School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, 85287
⁴Department of Chemistry, Oakland University, Rochester, Michigan, 48309
⁵Space Science and Engineering Division, Southwest Research Institute, San Antonio, Texas, 78228
Copyright Elsevier

Amide bonds are fundamental products in biochemistry, forming peptides critical to protein formation, but amide bonds are also detected in sterile environments and abiotic synthesis experiments. The abiotic formation of amide bonds may represent a prerequisite to the origin of life. Here we report thermodynamic models that predict optimal conditions for amide bond synthesis across geologically relevant ranges of temperature, pressure, and pH. We modeled acetamide formation from acetic acid and ammonia as a simple analog to peptide bond formation, and tested this model with hydrothermal experiments examining analogous reactions of amides including benzanilide and related structures. We also expanded predictions for optimizing diglycine formation, revealing that in addition to synthesis becoming more favorable at near-ambient pressures (Psat) with increasing temperatures, the strongest thermodynamic drive exists at extremely high pressures (> 15,000 bar) and decreasing temperatures. Beyond implications for life’s origins, the reactants and products involved in simple amide formation reactions can potentially be used as geochemical tracers for planetary exploration of environments that may be habitable.