^1,2Zelia Dionnet,^3,4,5Martin D. Suttle,^1,2Andrea Longobardo,^1,2Alessandra Rotundi,^3,4Luigi Folco,²Vincenzo Della Corte,⁶Andrew King
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13533]
¹Università di Napoli “Parthenope,” DIST, Centro Direzionale Isola C4, I‐80143 Naples, Italy
²INAF‐IAPS, via Fosso del Cavaliere 100, I‐00133 Rome, Italy
³Dipartimento di Scienze della Terra, Università di Pisa, V. S. Maria 53, I‐56126 Pisa, Italy
⁴Planetary Materials Group, Department of Earth Science, The Natural History Museum, Cromwell Rd, London, SW7 5BD UK
⁵Centro per l’Integrazione della Strumentazione dell’, Università di Pisa, Pisa, Italy
⁶PSICHE Beamline, Synchrotron SOLEIL, Gif‐Sur‐Yvette, France
Published by arrangement with John Wiley & Sons

Giant micrometeorites (MMs; 400–2000 µm) are exceedingly rare and scientifically valuable. Three‐dimensional nondestructive characterization by X‐ray computed tomography (X‐CT) provides information on the petrography and thus petrogenesis of MMs and serves as a guide to maximize subsequent multi‐analytical studies on such precious planetary materials. Here, we discuss the results obtained by X‐CT on 22 giant MMs and the classification based on their 3‐D density contrast images. Scoriaceous and unmelted MMs have distinct porosity ranges (10–40 vol% versus 0–25 vol%, respectively). We observe a porosity variation inside scoriaceous MMs, which allows their atmospheric entry flight history to be resolved. For the first time, spinning entry is explicitly demonstrated for four partially melted MMs. Furthermore, we are able to resolve the thermal gradient in a single particle, based on porosity variation (seen as a progressive increase in pore abundance and size with higher peak temperatures). Moreover, we explore parent body alteration through the 3‐D analysis of pores distribution, showing that shock fabrics are either absent or weakly developed in our data set. Finally, owing to the detection of pseudomorphic chondrules, we estimate that the intensively aqueously altered C1 or CI‐like material could represent 18% of the MM flux at this size fraction (400–1000 µm).

¹Christian Vollmer,¹Mandy Pelka,²Jan Leitner,³Arne Janssen
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13526]
¹Institut für Mineralogie, Westfälische Wilhelms‐Universität, Corrensstr. 24, 48149 Münster, Germany
²Particle Chemistry Department, Max Planck Institute for Chemistry, Hahn‐Meitner‐Weg 1, 55128 Mainz, Germany
³Materials Performance Centre, The University of Manchester, Oxford Road, Manchester, M13 9PL UK
Published by arrangement with John Wiley & Sons

Renazzo‐type (CR) carbonaceous chondrites belong to one of the most pristine meteorite groups containing various early solar system components such as matrix and fine‐grained rims (FGRs), whose formation mechanisms are still debated. Here, we have investigated FGRs of three Antarctic CR chondrites (GRA 95229, MIL 07525, and EET 92161) by electron microscopy techniques. We specifically focused on the abundances and chemical compositions of the amorphous silicates within the rims and matrix by analytical transmission electron microscopy. Comparison of the amorphous silicate composition to a matrix area of GRA 95229 clearly shows a compositional relationship between the matrix and the fine‐grained rim, such as similar Mg/Si and Fe/Si ratios. This relationship and the abundance of the amorphous silicates in the rims strengthen a solar nebular origin and rule out a primary formation mechanism by parent body processes such as chondrule erosion. Moreover, our chemical analyses of the amorphous silicates and their abundance indicate that the CR rims experienced progressive alteration stages. According to our analyses, the GRA 95229 sample is the least altered one based on its high modal abundance of amorphous silicates (31%) and close‐to‐chondritic Fe/Si ratios, followed by MIL 07525 and finally EET 92161 with lesser amounts of amorphous silicates (12% and 5%, respectively) and higher Fe/Si ratios. Abundances and chemical compositions of amorphous silicates within matrix and rims are therefore suitable recorders to track different alteration stages on a submicron scale within variably altered CR chondrites.

^1,2José C. Aponte,^1,2Hannah L. McLain,^1,3Danielle N. Simkus,¹Jamie E. Elsila,¹Daniel P. Glavin,¹Eric T. Parker,¹Jason P. Dworkin,⁴Dolores H. Hill,^4,5Harold C. Connolly Jr.,⁴Dante S. Lauretta
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13531]
¹Astrochemistry Laboratory, Code 691, NASA Goddard Space Flight Center, Greenbelt, Maryland, 20771 USA²Department of Chemistry, The Catholic University of America, Washington, District of Columbia, 20064 USA
³NASA Postdoctoral Program at NASA Goddard Space Flight Center, Greenbelt, Maryland, 20771 USA
⁴Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, 85721 USA
⁵School of Earth and Environment, Rowan University, Glassboro, New Jersey, 08028 USA
Published by arrangement with John Wiley & Sons

Evaluating the water‐soluble organic composition of carbonaceous chondrites is key to understanding the inventory of organic matter present at the origins of the solar system and the subsequent processes that took place inside asteroid parent bodies. Here, we present a side‐by‐side analysis and comparison of the abundance and molecular distribution of aliphatic amines, aldehydes, ketones, mono‐ and dicarboxylic acids, and free and acid‐releasable cyanide species in the CM2 chondrites Aguas Zarcas and Murchison. The Aguas Zarcas meteorite is a recent fall that occurred in central Costa Rica and constitutes the largest recovered mass of a CM‐type meteorite after Murchison. The overall content of organic species we investigated was systematically higher in Murchison than in Aguas Zarcas. Similar to previous meteoritic organic studies, carboxylic acids were one to two orders of magnitude more abundant than other soluble organic compound classes investigated in both meteorite samples. We did not identify free cyanide in Aguas Zarcas and Murchison; however, cyanide species analyzed after acid digestion of the water‐extracted meteorite mineral matrix were detected and quantified at slightly higher abundances in Aguas Zarcas compared to Murchison. Although there were differences in the total abundances of specific compound classes, these two carbonaceous chondrites showed similar isomeric distributions of aliphatic amines and carboxylic acids, with common traits such as a complete suite of structural isomers that decreases in concentration with increasing molecular weight. These observations agree with their petrologic CM type‐2 classification, suggesting that these meteorites experienced similar organic formation processes and/or conditions during parent body aqueous alteration.

^1,2Julia Semprich,¹Justin Filiberto
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13535]
¹Lunar and Planetary Institute, USRA, 3600 Bay Area Blvd., Houston, Texas, 77058 USA
²AstrobiologyOU, School of Environment, Earth and Ecosystem Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA UK
Published by arrangement with John Wiley & Sons

Here, we calculate the mineralogy of the Martian lower crust and upper mantle as a function of pressure and temperature with depth using four bulk compositions (average crust, Gusev basalt, olivine‐phyric shergottite, and primitive average mantle). We then use this mineralogy to extract rock properties such as density and seismic velocities, describe their changes with varying conditions and geotherms, and make predictions for the crust–mantle boundary. Mineralogically, all compositions produce garnet, orthopyroxene, clinopyroxene in varying proportions at high pressures, with differences in minor minerals (spinel, ilmenite, rutile, and/or K‐feldspar). According to our calculations, the average crust and Gusev basalt compositions have the potential to yield higher densities than the average mantle composition, particularly for thicker crusts and/or colder geotherms. Therefore, recycling of the Martian crust into the mantle could occur through the process of crustal delamination, if not kinetically inhibited. However, our results show that, depending on crustal thickness, the crust may not be easily distinguishable from the mantle in seismic properties.

¹Annarita Franza,²Giovanni Pratesi
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13525]
¹Department of Earth Sciences, University of Firenze, Via G. La Pira 4, 50121 Firenze, Italy
²¹INAF‐IAPS, Istituto di Astrofisica e Planetologia Spaziali, Via Fosso del Cavaliere 100, 00133 Roma, Italy
Published by arrangement with John Wiley & Sons

Julius Obsequens was the pseudonym of a Roman historian presumably living in the 4th century ad , whose life is shrouded in mystery. All that is known about Obsequens’s biography is that he was the author of a book entitled Liber Prodigiorum (Book of Prodigies ), a collection of prodigies deduced from Livy’s Ab Urbe Condita Libri (Books from the Founding of the City ). The Liber Prodigiorum covered the period from 190 to 11 bc and gathered a chronological list of portents of various kinds (e.g., births of monstrous animals or men, statues that shed blood, voices from beyond the grave, epidemics, earthquakes, unidentified flying objects). Among these extraordinary reports, chronicles of celestial phenomena were also included. The interdisciplinary approach adopted in this research has clarified the nature of the events described in the text and has enabled the identification of new Italian meteorite falls that are not included in the Meteoritical Bulletin Database.

^1,2Brant M. Jones,¹Aleksandr Aleksandrov,³M. Darby Dyar,⁴Charles A. Hibbitts,^1,2,4Thomas M. Orlando
Journal of Geophysical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2019JE006147]
¹School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA, USA
²Center for Space Technology and Research, Georgia Institute of Technology, Atlanta, GA, USA
³Planetary Science Institute, Tucson, AZ, USA
⁴John Hopkins Applied Physics Laboratory, Laurel, MD, USSchool of Physics, Georgia Institute of Technology, Atlanta, GA, USA
Published by arrangement with John Wiley & Sons

Desorption activation energies of chemisorbed water on Apollo lunar Samples 14163 and 10084 were determined by temperature program desorption (TPD) experiments conducted under ultrahigh vacuum conditions. Desorption at the grain/vacuum interface and desorption/transport of water though the porous medium with readsorption were found to reproduce the experimental TPD signal. Signal from the grain/vacuum interface yielded desorption activation energies and site probability distributions. Highland sample 14163 exhibited a broad distribution of binding site energies peaking at 60 kJ mol⁻¹, while mare sample 10084 exhibited a narrower distribution of binding site energies peaking at 65 kJ mol⁻¹. The highland sample adsorbed approximately 30% more water than the more space weathered and mature mare sample, suggesting maturity may not be a good predictor of the degree of molecular water uptake on lunar regolith. Water desorption from the lunar surface over a typical lunar day was simulated with the measured coverage‐dependent activation energies of the mare and highland samples. The resulting desorption profile of water through a lunar temperature cycle is in general agreement with Lunar Reconnaissance Orbiter (LRO) Lyman‐α Mapping Project (LAMP) spacecraft‐based observations of trends for both highland and mare assuming ~1% submonolayer coverage and that photon stimulated desorption is neglected.

¹G. M. Wong,^2,3,4J. M. T. Lewis,^3,4C. A. Knudson,^4,5M. Millan,³A. C. McAdam,³J. L. Eigenbrode,³S. Andrejkovičová,⁶F. Gómez,⁷R. Navarro‐González,¹C. H. House
Journal of Geophysical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2019JE006304]
¹Department of Geosciences, Pennsylvania State University, University Park, PA
²Department of Physics and Astronomy, Howard University, Washington, D.C.
³Planetary Environments Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD
⁴Center for Research and Exploration in Space Science and Technology, NASA GSFC, Greenbelt, MD
⁵Department of Biology, Georgetown University, Washington, DC
⁶Centro de Astrobiologia (CSIC‐INTA), Torrejón de Ardoz, Madrid, Spain
⁷Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Ciudad Universitaria, Ciudad de México, Mexico
Published by arrangement with John Wiley & Sons

The Mars Science Laboratory mission investigated Vera Rubin ridge, which bears spectral indications of elevated amounts of hematite and has been hypothesized as having a complex diagenetic history. Martian samples, including three drilled samples from the ridge, were analyzed by the Sample Analysis at Mars instrument suite via evolved gas analysis‐mass spectrometry (EGA‐MS). Here, we report new EGA‐MS data from Martian samples and describe laboratory analogue experiments. Analyses of laboratory analogues help determine the presence of reduced sulfur in Martian solid samples, which could have supported potential microbial life. We used evolved carbonyl sulfide (COS) and carbon disulfide (CS₂) to identify Martian samples likely to contain reduced sulfur by applying a quadratic discriminant analysis. While we report results for 24 Martian samples, we focus on Vera Rubin ridge samples and select others for comparison. Our results suggest the presence of reduced sulfur in the Jura member of Vera Rubin ridge, which can support various diagenetic history models, including, as discussed in this work, diagenetic alteration initiated by a mildly reducing, sulfite‐containing groundwater.

^1,2D. C. Hickson,³A. L. Boivin,⁴C. A. Tsai,¹M. G. Daly,³R. R. Ghent
Journal of Geophysical Research (Planets) (In Press) Link to Article [https://doi.org/10.1029/2019JE006141]
¹Centre for Research in Earth and Space Science, York University, Toronto, ON, Canada
²Arecibo Observatory, University of Central Florida, PR, USA
³Solar System Exploration Group, Department of Earth Sciences, University of Toronto, Toronto, ON, Canada
⁴Department of Physics, University of Toronto, Toronto, ON, Canada
Published by arrangement with John Wiley & Sons

Planetary radar has provided a growing number of datasets on the inner planets and near‐Earth and main‐belt asteroid populations in the solar system. Physical interpretation of radar data for inference of surface properties requires constraints on the constitutive parameters of the material making up a given surface. In this study, the complex permittivity of seven minerals as a function of frequency and porosity is measured using the coaxial transmission line method to determine the mixing equation that best describes the relationship between the real part of the complex permittivity of single mineral crystals and granular mineral powders. We find the Looyenga‐Landau‐Lifshitz and Bruggeman Symmetric mixing equations to describe our experimental results with the highest accuracy. The variation in the real part of the permittivity of solid mineral crystals between different minerals is shown to depend on the grain density and the chemical composition of the minerals. These mixing relationships are incorporated into an asteroid radar model and used to calculate the porosity in the near‐surface of seven asteroids visited by robotic spacecraft using Earth‐based radar observations. The results of the asteroid radar model support the presence of significant porosity in the boulders on the surface of asteroid 101955 Bennu. This research highlights the ability of radar to measure the porosity on asteroid surfaces and provides theoretical and experimental justification for the inversion of permittivity to bulk density assumed by the asteroid radar model.

¹Amy C. McAdam et al. (>10)
Journal of Geophysical Research (Planets) (In Press) Link to Article [https://doi.org/10.1029/2019JE006309]
¹NASA Goddard Space Flight Center, Greenbelt, MD, USA
Published by arrangement with John Wiley & Sons

Vera Rubin ridge (VRR) is a topographic high within the layers of Mount Sharp, Gale crater, that exhibits a strong hematite spectral signature from orbit. The Mars Science Laboratory Curiosity rover carried out a comprehensive investigation to understand the depositional and diagenetic processes recorded in the rocks of VRR. Sample Analysis at Mars (SAM) evolved gas analyses (EGA) were performed on three samples from the ridge and one from directly beneath the ridge. SAM evolved H2O data suggested the presence of an Fe‐rich dioctahedral smectite, such as nontronite, in the sample from beneath the ridge. H2O data are also consistent with ferripyrophyllite in VRR samples. SAM SO2 data indicated that all samples contained Mg sulfates, and some Fe sulfate. Several volatile detections suggested trace reduced sulfur sources, such as Fe sulfides and/or S‐bearing organic compounds, in two samples while significant O2 and NO evolved from one sample indicated the presence of oxychlorine and nitrate/nitrite salts, respectively. The O2 evolution was the second highest to date and the first observed in ~1200 sols. HCl released from all samples likely resulted, in part, from trace chloride salts. All samples evolved CO2 and CO consistent with oxidized carbon compounds (e.g., oxalates), while some CO2 may result from carbonate. SAM‐derived constraints on the mineralogy and chemistry of VRR materials, in the context of additional mineralogy, geochemistry, and sedimentology information obtained by Curiosity , support a complex diagenetic history that involved fluids of a range of possible salinities, redox characteristics, pHs, and temperatures.

¹Nicole X.Nie,¹Nicolas Dauphas,¹Krysten L.Villalon,²Nan Liu,¹Andy W.Heard,³Richard V.Morris,⁴Stanley A.Mertzman
Earth and Planetary Science Letters 544, 116385 Link to Article [https://doi.org/10.1016/j.epsl.2020.116385]
¹Origins Laboratory, Department of the Geophysical Sciences and Enrico Fermi Institute, The University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60637, USA
²Department of Physics, Washington University in St. Louis, St. Louis, MO 63130, USA
³ NASA Johnson Space Center, Houston, TX, 77058, USA
⁴Department of Earth and Environment, Franklin and Marshall College, Lancaster, PA 17604-3003, USA
Copyright Elsevier

We cannot reproduce the abstract of this paper for technical reasons