Dust/ice mixing in cold regions and solid-state water in the diffuse interstellar medium

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

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Trajectory and orbit of the unique carbonaceous meteorite Flensburg

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.

Mid-infrared reflectance spectroscopy of synthetic glass analogs for mercury surface studies

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.


Cohesion of regolith: Measurements of meteorite powders

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.

Round up the unusual suspects: Near-Earth Asteroid 17274 (2000 LC16) a plausible D-type parent body of the Tagish Lake meteorite

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.

Multi-collector 40Ar/39Ar dating of microtektites from Transantarctic Mountains (Antarctica): a definitive link with the Australasian tektite/microtektite strewn field

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.

Quantifying the Extent of Amide and Peptide Bond Synthesis Across Conditions Relevant to Geologic and Planetary 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.

Evaluating the O‐Cr‐Mo isotope signatures in various meteorites representing core–mantle–crust fragments: Implications for partially differentiated planetesimal(s) accreted in the early outer solar system

1Arshad Ali,2Iffat Jabeen
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13627]
1Earth Sciences Research Centre (ESRC), Sultan Qaboos University, Al‐Khoudh, Muscat 123, Sultanate of Oman
2Department of Earth Sciences, University of Western Ontario, London, Ontario, N6A 3K7 Canada
Published by arrangement with John Wiley & Sons

The Allende, Eagle Station pallasites (ESP), some ungrouped achondrites (UA), and ungrouped irons (UI) represent different types of meteorites; these are traditionally distinguished as chondrule‐bearing chondrite, chondrule‐free stony irons, stones, and irons, respectively. Oxygen isotopic compositions of meteorites have long been used as a robust tool to identify the parent bodies of these extraterrestrial materials. We revisited the δ18O‐∆17O, along with ε54Cr and ε92Mo, of these meteorites and established a genetic link that possibly suggests that undifferentiated carbonaceous chondrites and their differentiated counterparts belong to a common reservoir. We observed that the differentiated counterparts of Allende CV3 including ESP, ungrouped achondrites, and ungrouped irons collectively provide the oxygen isotope trends comparable to those of the Y&R and the PCM lines, and are likely to represent the primitive isotope reservoirs in the solar nebula. ε54Cr and ε92Mo data of these meteorite types support their oxygen isotope trends. The idea of a common partially differentiated parent body also lends support from natural remnant magnetization in the CV chondrites and Eagle Station olivine. Furthermore, ∆17O‐ε54Cr data suggest that these meteorites originated from carbonaceous planetesimal(s) accreted at different heliocentric distances in the solar nebula in the outer solar system. As proposed earlier, these bodies remained separated from the inner solar system due to formation of Jupiter. Taken together, we propose that the ungrouped irons, ESP, and ungrouped achondrites could possibly represent the differentiated sections, such as core, core–mantle, and mantle of a planetesimal(s), respectively, with the Allende CV3 representing an undifferentiated chondritic crust.

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