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.