¹R.V.Morris et al. (>10)
Journal of Geophysical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2019JE006324]
¹NASA Johnson Space Center, Houston, TX, USA
Published by arrangement with John Wiley & Sons

Hydrothermal high sanidine and specular hematite are found within ferric‐rich and grey‐colored cemented basaltic breccia occurring within horizontal, weathering‐resistant strata exposed in an erosional gully of the Pu’u Poliahu cinder cone in the summit region of Maunakea volcano (Hawai’i). The cone was extensively altered by hydrothermal, acid‐sulfate fluids at temperatures up to ~400 °C, and, within strata, plagioclase was removed by dissolution from progenitor Hawaiitic basalt, and sanidine and hematite precipitated. Fe2O3T concentration and Fe3+/∑Fe redox state are ~12 wt. % and ~0.4 for progenitor basalt and 46‐60 wt. % and ~1.0 for cemented breccias, respectively, implying open‐system alteration and oxic precipitation. Hydrothermal high sanidine (adularia) is characterized by full Al,Si structural disorder with monoclinic unit‐cell (Rietveld refinement): a = 8.563(19) Å, b = 13.040(6) Å, c = 7.169(4) Å, β = 116.02(10)° and V = 719.4(19) Å3. Hematite (structure confirmed by Rietveld refinement) is the predominant Fe‐bearing phase detected. Coarse size fractions of powdered hematite‐rich breccia (500–1000 μm) are dark and spectrally neutral at visible wavelengths, confirming specular hematite, and SEM images show platy to polyhedral hematite morphologies with longest dimensions >10 μm. Smectite and a 10‐Å phyllosilicate, both chemically dominated by Mg as octahedral cation, are additional diagenetic hydrothermal alteration products. By analogy and as a working hypothesis, high sanidine (Kimberly formation) and specular hematite (Mt. Sharp group at Hartmann’s Valley and Vera Rubin ridge) at Gale crater are interpreted as diagenetic alteration products of martian basaltic material by hydrothermal processes.

¹D.Das et al. (>10)
Journal of Geophysical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2019JE006301]
¹Department of Earth and Planetary Sciences, McGill University, Quebec, Canada
Published by arrangement with John Wiley & Sons

The NASA Curiosity rover’s ChemCam instrument suite has detected boron in calcium‐sulfate‐filled fractures throughout the sedimentary strata of Gale crater including Vera Rubin ridge (VRR). The presence of elevated B concentration provides insights into Martian subsurface aqueous processes. In this study we extend the dataset of B in Ca‐sulfate veins across Gale crater, comparing the detection frequency and relative abundances with Li. We report 33 new detections of B within veins analyzed between sols 1548 and 2311 where detections increase in Pettegrove Point and Jura members, which form VRR. The presence of B and Li in the Ca‐sulfate veins is possibly due to dissolution of pre‐existing B in clays of the bedrock by acids or neutral water and redistribution of the elements into the veins. Elevated frequency of B detection in veins of Gale crater correlate with presence of dehydration features such as desiccation cracks, altered clay minerals and detections of evaporites such as Mg‐sulfates, chloride salts in the host rocks. The increased observations of B also coincide with decreased Li concentration in the veins (average Li concentration of veins drops by ~15 ppm). Boron and Li have varying solubilities and Li does not form salts as readily upon dehydration as B, causing it to remain in the solution. So, the weak negative correlation between B and Li may reflect the crystallization sequence during dehydration on Vera Rubin ridge.

¹L.Krämer-Rugiu (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13534]
¹Aix Marseille University, CNRS, Coll France, IRD, INRAE, CEREGE, Aix‐en‐Provence, France
Published by arrangement with John Wiley & Sons

Caleta el Cobre (CeC) 022 is a Martian meteorite of the nakhlite group, showing an unbrecciated cumulate texture, composed mainly of clinopyroxene and olivine. Augite shows irregular core zoning, euhedral rims, and thin overgrowths enriched in Fe relative to the core. Low‐Ca pyroxene is found adjacent to olivine. Phenocrysts of Fe‐Ti oxides are titanomagnetite with exsolutions of ilmenite/ulvöspinel. Intercumulus material consists of both coarse plagioclase and fine‐grained mesostasis, comprising K‐feldspars, pyroxene, apatite, ilmenite, Fe‐Ti oxides, and silica. CeC 022 shows a high proportion of Martian aqueous alteration products (iddingsite) in olivine (45.1 vol% of olivine) and mesostasis. This meteorite is the youngest nakhlite with a distinct Sm/Nd crystallization age of 1.215 ± 0.067 Ga. Its ejection age of 11.8 ± 1.8 Ma is similar to other nakhlites. CeC 022 reveals contrasted cooling rates with similarities with faster cooled nakhlites, such as Northwest Africa (NWA) 817, NWA 5790, or Miller Range 03346 nakhlites: augite irregular cores, Fe‐rich overgrowths, fine‐grained K‐feldspars, quenched oxides, and high rare earth element content. CeC 022 also shares similarities with slower cooled nakhlites, including Nakhla and NWA 10153: pyroxene modal abundance, pyroxenes crystal size distribution, average pyroxene size, phenocryst mineral compositions, unzoned olivine, and abundant coarse plagioclase. Moreover, CeC 022 is the most magnetic nakhlite and represents an analog source lithology for the strong magnetization of the Martian crust. With its particular features, CeC 022 must originate from a previously unsampled sill or flow in the same volcanic system as the other nakhlites, increasing Martian sample diversity and our knowledge of nakhlites.

¹Philip T.Metzger,²Daniel T.Britt
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2020.113904]
¹Florida Space Institute, University of Central Florida, Orlando, Florida, USA
²Department of Physics, University of Central Florida, Orlando, Florida, USA
Copyright Elsevier

When creating asteroid regolith simulant, it is necessary to have a model of asteroid regolith to guide and to evaluate the simulant. We created a model through evaluation and synthesis of the available data sets including (1) the returned sample from Itokawa by the Hayabusa spacecraft, (2) imagery from the Hayabusa and NEAR spacecraft visiting Itokawa and Eros, respectively, (3) thermal infrared observations from asteroids, (4) the texture of meteorite regolith breccias, and (5) observations and modeling of the ejecta clouds from disrupted asteroids. Comparison of the Hayabusa returned sample with other data sets suggest the surficial material in the smooth regions of asteroids is dissimilar to the bulk regolith, probably due to removal of fines by photoionization and solar wind interaction or by preferential migration of mid-sized particles into the smooth terrain. We found deep challenges interpreting and applying the thermal infrared data so we were unable to use those observations in the model. Texture of regolith breccias do not agree with other data sets, suggesting the source regolith on Vesta was coarser than typical asteroid regolith. The observations of disrupted asteroids present a coherent picture of asteroid bulk regolith in collisional equilibrium, unlike lunar regolith, HED textures, and the Itokawa returned sample. The model we adopt consists of power laws for the bulk regolith in unspecified terrain (differential power index −3.5, representing equilibrium), and the surficial regolith in smooth terrain (differential power index −2.5, representing disequilibrium). Available data do not provide adequate constraints on maximum and minimum particle sizes for these power laws, so the model treats them as user-selectable parameters for the simulant.

^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.