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.

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.

Luleå University of Technology has a number of job opportunities in planetary science at its Space Campus in Kiruna:
Specifically, we have just released vacancy notices for one senior lecturer (somewhat similar to associate professor in the US or senior lecturer in the UK, tenure), one associate senior lecturer (equivalent to lecturer/assistant professor, tenure track) and a postdoc (2 year fixed-term).
You can find the vacancy notices here:

365-2021: https://www.ltu.se/ltu/Lediga-jobb?l=en&rmpage=job&rmjob=4396&rmlang=UK
366-2021: https://www.ltu.se/ltu/Lediga-jobb?l=en&rmpage=job&rmjob=4398&rmlang=UK
364-2021: https://www.ltu.se/ltu/Lediga-jobb?l=en&rmpage=job&rmjob=4400&rmlang=UK

^1,2Samuel P. Alpert,^1,2Denton S. Ebel,^1,2,3Michael K. Weisberg,
^1,4Jeremy R. Neiman
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13619]
¹Department of Earth and Planetary Sciences, American Museum of Natural History, New York, New York, 10024 USA
²Department of Earth and Environmental Sciences, CUNY Graduate Center, New York, New York, 10016 USA
³Department of Physical Sciences, Kingsborough Community College, CUNY, Brooklyn, New York, 11235 USA
⁴Python developer and participant in the American Museum of Natural History “Hack the Solar System” 2019 Hackathon.
Published by arrangement with John Wiley & Sons

Opaque assemblages (OAs) are small (submillimeter) objects composed primarily of metals, sulfides, and oxides that exist in nearly all chondritic meteorite groups as discrete objects in the matrix or associated with chondrules. The size, morphology, and petrology of OAs vary greatly between different chondrite groups, with petrologic grade within a single group, and by their apparent textural setting. Two hypotheses may explain the formation of matrix OAs: (1) they were separated from chondrules via surface tension during heating events, or (2) they formed as free‐floating objects in the solar nebula; however, this is the first comprehensive study of the petrology of OAs in ordinary chondrites (OCs) as a group, which seeks to determine if one hypothesis is sufficient to explain all such objects. Here, we use a newly developed machine learning algorithm to show that all OAs from the least equilibrated OC, Semarkona (LL 3.01), are composed of kamacite, taenite, troilite, pentlandite, magnetite, and other minor phases. These OAs form two distinct groups based on their modal mineralogy: one group in and associated with chondrules, and the other group free‐floating in the matrix. Chondrule OAs exhibit a bimodal distribution between sulfide‐ and metal‐rich endmembers in agreement with previous findings. Matrix OAs cluster at roughly equal abundances of sulfides and metals and universally exhibit magnetite rims. The two populations of chondrule OAs cannot be combined to form the modal mineralogies observed in matrix OAs and some matrix OAs exhibit mineralogical layering consistent with fractional condensation. Both observations support the hypothesis that matrix OAs were not formed by expulsion from chondrules and instead formed as free‐floating objects in the solar nebula; however, chondrule OAs must have formed with their host chondrules during heating events.

¹Stefan Loehle,¹Martin Eberhart,¹Fabian Zander,¹Arne Meindl,²Regina Rudawska,²Detlef Koschny,²Joe Zender,³Ron Dantowitz,⁴Peter Jenniskens
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13622]
¹Institut für Raumfahrtsysteme, Universität Stuttgart, Stuttgart, 70569 Germany
²ESA ESTEC, Noordwijk, 2201 The Netherlands
³Dexter Southfield, Boston, MA02445 Massachusetts, USA
⁴SETI Institute, Mountain View, CA94043 California, USA
Published by arrangement with John Wiley & Sons

The advancement in the acquisition of spectral data from meteors, as well as the capability to analyze meteoritic entries in ground testing facilities, requires the assessment of the performance of software tools for the simulation of spectra for different species. The Plasma Radiation Database, PARADE, is a line‐by‐line emission calculation tool. This article presents the extensions implemented for the simulation of meteor entries with the additional atomic species Na, K, Ti, V, Cr, Mn, Fe, Ca, Ni, Co, Mg, Si, and Li. These atoms are simulated and compared to ground testing spectra and to observed spectra from the CILBO observatory. The diatomic molecules AlO and TiO have now been added to the PARADE database. The molecule implementations have been compared to the results of a simple analytical program designed to approximate the vibrational band emission of diatomic molecules. AlO and TiO have been identified during the airborne observation campaigns of re‐entering man‐made objects WT1190F and CYGNUS OA6. Comparisons are provided showing reasonable agreement between observation and simulation.

^1,2,3Imene Kerraouch et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13620]
¹Institut für Planetologie, University of Münster, Wilhelm‐Klemm Str. 10, Münster, D‐48149 Germany
²Astromaterials Research and Exploration Science, NASA Johnson Space Center, Houston, Texas, 77058 USA
³Department of Geology, University of Science and Technology Houari Boumediene (USTHB), Bab Ezzouar, 16111 Algeria
Published by arrangement with John Wiley & Sons

On April 23, 2019, a meteorite fall occurred in Aguas Zarcas, Costa Rica. According to the Meteoritical Bulletin, Aguas Zarcas is a brecciated CM2 chondrite dominated by two lithologies. Our X‐ray computed tomography (XCT) results show many different lithologies. In this paper, we describe the petrographic and mineralogical investigation of five different lithologies of the Aguas Zarcas meteorite. The bulk oxygen isotope compositions of some lithologies were also measured. The Aguas Zarcas meteorite is a breccia at all scales. From two small fragments, we have noted five main lithologies, including (1) Met‐1: a metal‐rich lithology; (2) Met‐2: a second metal‐rich lithology which is distinct from Met‐1; (3) a brecciated CM lithology with clasts of different petrologic subtypes; (4) a C1/2 lithology; and (5) a C1 lithology. The Met‐1 lithology is a new and unique carbonaceous chondrite which bears similarities to CR and CM chondrite groups, but is distinct from both based on oxygen isotope data. Met‐2 also represents a new type of carbonaceous chondrite, but it is more similar to the CM chondrite group, albeit with a very high abundance of metal. We have noted some similarities between the Met‐1 and Met‐2 lithologies and will explore possible genetic relationships. We have also identified a brecciated CM lithology with two primary components: a chondrule‐poor lithology and a chondrule‐rich lithology showing different petrologic subtypes. The other two lithologies, C1 and C1/2, are very altered and possibly related to the CM chondrite group. In this article, we describe all the lithologies in detail and attempt a classification of each in order to understand the origin and the history of formation of the Aguas Zarcas parent body.