¹Alessandro Pisello,²Marco Ferrari,²Simone De Angelis,^1,2,3Francesco P.Vetere,¹Massimiliano Porreca,²Stefania Stefani,¹Diego Perugini
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.115222]
¹Department of Physics and Geology, University of Perugia, I-06123 Perugia, Italy
²Institute for Space Astrophysics and Planetology, INAF, Rome, Italy
³Department of Physical Sciences, Earth and Environment, University of Siena, 53100, Italy
Copyright Elsevier

Volcanic phenomaena shaped the surface of all terrestrial planets in the solar system, and silicate glasses represent a major component in pyroclastic deposits and lavas. Spectral features of silicate glasses therefore influence spectral characteristics of large portions of planetary surfaces.

In this study, experimental petrology techniques have been used to produce 19 silicate glass samples having natural chemical composition corresponding to four of the most common magmatic series on planet Earth. Reflectance of such products was investigated in the mid-infrared region (MIR) to observe the evolution of their spectral characteristics with changing degree of evolution (expressed as silica content) and alkaline content. We have observed how chemical features have a clear influence in shifting the spectral features (to lower wavelengths with increasing silica, such as for previously studied volcanic rocks) and on the spectral shape, which is substantially different between mafic and highly silicic products. This allowed us to propose a model to retrieve chemical information (SiO2 and SiO2 + Al2O3 + TiO2 content) from the wavelength at which spectral features (CF and RBpeak) occur. Moreover, by comparing our results with previous MIR studies we have observed that our model can be applied, to a certain extent, to interpret chemical fingerpint volcanic rocks in general. Here, it is also shown how granulometry influences spectral shape, but does not affect spectral shift.

This study will be useful to interpret planetary information and assess how amorphous silicate phases influence spectral characteristics of volcanic areas on planetary surfaces.

¹S.A.Crowther,¹P.L.Clay,¹S.Edwards,²H.Busemann,¹K.H.Joy,¹A.A.Early,¹R.Burgess,³A.R.Butcher,⁴M.Humay,¹J.D.Gilmour
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2022.08.002]
¹Department of Earth and Environmental Sciences, The University of Manchester, UK
²ETH Zürich, Institut für Geochemie und Petrologie, Zürich, Switzerl
³Geological Survey of Finland GTK, Espoo, Finland
⁴National High Magnetic Field Laboratory and Department of Earth, Ocean and Atmospheric Science, Florida State University, Tallahassee, USA
Copyright Elsevier

The martian meteorite Northwest Africa (NWA) 8114 is a regolith breccia grouped with the NWA 7034 (‘Black Beauty’) stone and others. The meteorite, with its complex rock and mineral load, records over 4.4 billion years of martian geological and atmospheric history. In this work we present new analyses of noble gases in NWA 8114, and consider the constraints they impose on the evolution of the martian atmosphere over the past 4 billion years. We also report a petrographic overview, halogen abundances, and an argon isotope age, which provide context for interpreting the noble gas data.

The krypton and xenon elemental signature of NWA 8114 is elementally fractionated with respect to the present-day martian atmosphere as measured in shergottite glasses; there is no requirement for a contribution from the ancient martian atmosphere in our data. The xenon isotopic composition incorporates (i) a component enriched in 129Xe (maximum 129Xe/132Xe = 2.450 ± 0.045 compared with a solar ratio of ∼1), which is similar to the present day martian atmosphere, (ii) a cosmic-ray spallation component dominated by production from barium, and (iii) a fission component. We estimate a cosmic ray exposure (CRE) age of 5.7 ± 1.3 Myr from cosmogenic 21Ne and 38Ar.

Understanding how the martian atmosphere has changed through the planet’s history is a key part of understanding the planet’s geological history and evolution. We develop a model for the evolution of the martian atmosphere constrained by the amount of spallation-derived xenon in the atmosphere today and the evolution of the 129Xe/132Xe ratio over time. A baseline model in which the early atmosphere collapsed 3.7 Gyr ago (and assuming no further loss) requires a constant degassing of the crustal budget of spallation xenon of 0.034 % Myr-1 to accumulate sufficient spallation-derived xenon in the atmosphere. Combining constraints imposed by the 129Xe/132Xe ratio with the spallation budget requires loss of xenon from the martian atmosphere over the last 3.7 Gyr, with the present day budget being as little as 20 % of that at the start of this period.

Due to conferences and technical issues, the will be another short Summer Break.

^1,2G.Caravaca et al. (>10)
Journal of Geophysical Research (Planets) Open Access Link to Article [https://doi.org/10.1029/2021JE007093]
¹UMR 5277 CNRS, UPS, CNES Institut de Recherche en Astrophysique et Planétologie, Université Paul Sabatier Toulouse III, Toulouse, France
²UMR 6112 CNRS Laboratoire de Planétologie et Géosciences, Nantes Université, Université d’Angers, Nantes, France
Published by arrangement with John Wiley & Sons

Between January 2019 and January 2021, the Mars Science Laboratory team explored the Glen Torridon region in Gale crater (Mars), known for its orbital detection of clay minerals. Mastcam, MAHLI and ChemCam data are used in an integrated sedimentological and geochemical study to characterize the Jura member of the upper Murray formation and the Knockfarril Hill member of the overlying Carolyn Shoemaker formation in northern Glen Torridon. The studied strata show a progressive transition represented by interfingering beds of fine-grained, recessive mudstones of the Jura member and coarser-grained, cross-stratified sandstones attributed to the Knockfarril Hill member. Whereas the former are interpreted as lacustrine deposits, the latter are interpreted as predominantly fluvial deposits. The geochemical composition seen by the ChemCam instrument show K2O-rich mudstones (∼1-2 wt.%) vs MgO-rich sandstones (>6 wt.%), relative to the average composition of the underlying Murray formation. We document consistent sedimentary and geochemical datasets showing that low-energy mudstones of the Jura member are associated with the K-rich endmember, and that high-energy cross-stratified sandstones of the Knockfarril Hill member are associated with the Mg-rich endmember, regardless of stratigraphic position. The Jura to Knockfarril Hill transition therefore marks a significant paleoenvironmental change, where a long-lived and comparatively quiescent lacustrine setting progressively changes into a more energetic fluvial setting, as a consequence of shoreline regression due to either increased sediment supply or lake-level drop.

¹A.C.McAdam et al. (>10)
Journal of Geophysical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2022JE007179]
¹NASA Goddard Space Flight Center, Greenbelt, MD, USA
Published by arrangement with John Wiley & Sons

Evolved gas analysis (EGA) data from the Sample Analysis at Mars (SAM) instrument suite indicated Fe-rich smectite, carbonate, oxidized organics, Fe/Mg sulfate, and chloride in sedimentary rocks from the Glen Torridon (GT) region of Gale crater that displayed phyllosilicate spectral signatures from orbit. SAM evolved H2O data indicated that the primary phyllosilicate in all GT samples was an Fe-rich dioctahedral smectite (e.g., nontronite) with lesser amounts of a phyllosilicate such as mixed layer talc-serpentine or greenalite-minnesotaite. CO2 data supported the identification of siderite in several samples, and CO2 and CO data was also consistent with trace oxidized organic compounds such as oxalate salts. SO2 data indicated trace and/or amorphous Fe sulfates in all samples and one sample may contain Fe sulfides. SO2 data points to significant Mg sulfates in two samples, and lesser amounts in several other samples. A lack of evolved O2 indicated the absence of oxychlorine salts and Mn3+/ Mn4+ oxides. The lack of, or very minor, evolved NO revealed absent or very trace nitrate/nitrite salts. HCl data suggested chloride salts in GT samples. Constraints from EGA data on mineralogy and chemistry indicated that the environmental history of GT involved alteration with fluids of variable redox potential, chemistry and pH under a range of fluid-to-rock ratio conditions. Several of the fluid episodes could have provided habitable environmental conditions and carbon would have been available to any past microbes though the lack of significant N could have been a limiting factor for microbial habitability in the GT region.

¹Randy L. Korotev
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13900]
¹Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University, Saint Louis, Missouri, 63130 USA
Published by arrangement with John Wiley & Sons

Bulk composition data for 24 chemical elements are presented for regolith samples (<1 mm fines) from each of the 62 half-centimeter dissection intervals along the 31 cm length of the 76001 vertical drive tube collected by astronauts at the base of the North Massif at station 6 of the Apollo 17 landing site. The core regolith is nearly uniform in composition with depth although the concentrations of Sc and Sm, for example, decrease from 28.5 μg g−1 Sc and 5.93 μg g−1 Sm at the top 2.5 cm to 26.9 μg g−1 Sc and 5.55 μg g−1 Sm at the bottom 2.5 cm. This change reflects an increase with depth in the relative abundance of Sm-poor, feldspathic material, from 48.4% at the top to 50.1% at the bottom. On the basis of compositional mass balance, the feldspathic (nonmare) material of the station 6 regolith requires a substantial proportion of an Mg-rich lithology, ~27% when modeled as troctolite sample 76535. The remaining 73% is nominally Sm-poor anorthositic norite in composition. No such Mg-rich component is required to account for the composition of the regolith of the South Massif (stations 2 and 3). The total feldspathic component of the North Massif regolith, normatively an anorthositic troctolite (74 vol% plagioclase, olivine:pyroxene = 55:45, Mg′ = 78%), is very similar to that of the nonmare component of the Luna 20 regolith collected 910 km to the southeast on the Crisium ejecta deposit. We also present new composition data for 21, 25, and 16 small lithic fragments (0.1–3.9 mg each) from the regoliths of the Luna 16, 20, and 24 missions.

¹Cyrena A. Goodrich et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13889]
¹Lunar and Planetary Institute, Universities Space Research Association, 3600 Bay Area Blvd., Houston, Texas, 77058 USA
Published by arrangement with John Wiley & Sons

MS-MU-012, a 15.5 g clast from the Almahata Sitta polymict ureilite, is the first known plagioclase-bearing main group ureilite. It is a coarse-grained (up to 4 mm), equilibrated assemblage of 52% olivine (Fo 88), 13% orthopyroxene (Mg# 89.2, Wo 4.5), 11% augite (Mg# 90.2, Wo 37.3), and 14% plagioclase (An 68), plus minor metal and sulfide. The plagioclase grains have been secondarily remelted and internally recrystallized, but retain primary external morphologies. Melt inclusions occur in olivine. Rounded chadocrysts of olivine and orthopyroxene are enclosed in augite grains. In terms of texture, mineralogy, major and minor element mineral compositions, and oxygen isotopes, MS-MU-012 is virtually identical to the archetypal Hughes-type main group ureilites, with the significant addition of primary plagioclase. We conclude that MS-MU-012 formed as a cumulate in a common lithologic unit with the Hughes-type ureilites. Based on reconstructed compositions of melts trapped in olivine, orthopyroxene, and augite in the Hughes-type samples, we infer that the parent magma of the Hughes unit originated as a late melt in the incremental melting of the ureilite parent body (UPB), near the end of the melting sequence, but was not completely extracted from the mantle like earlier melts and was emplaced in an intrusive body. MELTS calculations indicate that olivine began to crystallize at ~1260 °C, followed shortly thereafter by co-crystallization of orthopyroxene and augite. Plagioclase began to crystallize at ~1170–1180 °C. Graphite was buoyant in the melt and became heterogeneously distributed in flotation cumulates. Residual silicate liquid was extracted from the cumulate pile and could have crystallized to form the “labradoritic melt lithology” (with plagioclase of An ~68-35), which is partially preserved as clasts in polymict ureilites. The final equilibration temperature recorded by the Hughes unit was ~1140–1170 °C, just before catastrophic disruption of the UPB. MS-MU-012 provides a critical missing link in the differentiation history of this asteroid.

^1,2Peter Jenniskens,²Darrel Robertson,³Cyrena A. Goodrich,⁴Muawia H. Shaddad,⁴Ayman Kudoda,⁵Anna M. Fioretti,⁶Michael E. Zolensky
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.13892]
¹SETI Institute, 339 Bernardo Avenue, Mountain View, California, 94043 USA
²NASA Ames Research Center, Moffett Field, California, 94035 USA
³Lunar and Planetary Institute, USRA, Houston, Texas, 77058 USA
⁴Department of Physics and Astronomy, University of Khartoum, Khartoum, 11115 Sudan
⁵CNR–Istituto di Geoscienze e Georisorse, I-35131 Padova, Italy
⁶Astromaterials Research and Exploration Science, NASA Johnson Space Center, Houston, Texas, 77058 USA
Published by arrangement with John Wiley & Sons

Asteroid 2008 TC3 impacted the Earth’s atmosphere with a known shape and orientation. Over 600 meteorites were recovered at recorded locations, including meteorites of nonureilite type. From where in the asteroid did these stones originate? Here, we reconstruct the meteor lightcurve and study the breakup dynamics of asteroid 2008 TC3 in 3-D hydrodynamic modeling. Two fragmentation regimes are found that explain the lightcurve and strewn field. As long as the asteroid created a wake vacuum, the fragments tended to move into that shadow, where they mixed with small relative velocities and surviving meteorites fell along a narrow strip on the ground. But when the surviving part of the backside and bottom of the asteroid finally collapsed at 33 km altitude, it created an end flare and dust cloud, while fragments were dispersed radially with much higher relative speed due to shock–shock interactions with a distorted shock front. Stones that originated in this final collapse tended to survive in a larger size and fell over a wider area at locations on the ground. Those locations to some extent still trace back to the fragment’s original position in the asteroid. We classified the stones from this “large mass” area and used this information to glean some insight into the relative location of recovered ureilites and ordinary and enstatite chondrites in 2008 TC3.

¹Taha Shisseh,¹Hasnaa Chennaoui Aoudjehane,²Carl B. Agee,³Omar Boudouma
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13899]
¹GAIA Laboratory, Faculty of Sciences Ain Chock, Hassan II University of Casablanca, km 8 Route d’El Jadida, 20150 Casablanca, Morocco
²Institute of Meteoritics, University of New Mexico, Albuquerque, New Mexico, 87131 USA
³UPMC – Paris 06, UMR, 7193 Paris, France
Published by arrangement with John Wiley & Sons

Tirhert and Aouinet Legraa are the only documented unbrecciated eucrite falls in Africa. Aouinet Legraa fell in Algeria on July 17, 2013. Tirhert’s fall occurred about a year later in Morocco, on July 9, 2014. Both meteorites are covered by a black and glossy fusion crust as is typical of eucrites. Tirhert has a poikilitic texture with remnant subophitic pockets, and consists of millimeter-sized grains of plagioclase (An87-91), pigeonite (Mg# 42) with augite exsolution lamellae, and interstitial opaque minerals. Aouinet Legraa has a subophitic texture, and it is dominated by plagioclase laths (An82-89) enclosed by pigeonite (Mg# 37), with exsolution lamellae of augite. Remnant Ca zoning in pyroxene is observed in both rocks, although it is more abundant in Aouinet Legraa than Tirhert. The presence of exsolved pyroxenes suggests that these meteorites have undergone thermal metamorphism. Equilibration temperatures estimated from pigeonite and augite pairs using the QUILF program are ∼931 °C in Tirhert and ∼758 °C in Aouinet Legraa. This indicates that these rocks had distinct thermal histories. Aouinet Legraa has trace element abundances similar to the typical main group eucrite Juvinas, confirming its origin as a main group eucrite. The trace element abundances of Tirhert fall between those of cumulate and main group eucrites. Its rare earth element pattern is flat with a positive Eu anomaly. This likely suggests that Tirhert is a partial cumulate of plagioclase from a main group magma, or a flotation cumulate formed by flotation of plagioclase in a subvolcanic chamber or by scavenging crystals during eruption.

¹Yves Marrocchi,¹Maxime Piralla,¹Maxence Regnault,²Valentina Batanova,¹Johan Villeneuve,³Emmanuel Jacquet
Earth and Planetary Science Letters 593, 117683 Link to Article [https://doi.org/10.1016/j.epsl.2022.117683]
¹Université de Lorraine, CNRS, CRPG, UMR 7358, Vandœuvre-lès-Nancy 54500, France
²Université Grenoble Alpes, ISTerre, CNRS, UMR 5275, Grenoble 38000, France
³Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC), Muséum national d’Histoire naturelle, Sorbonne Université, CNRS; CP52, 57 rue Cuvier, 75005 Paris, France
Copyright Elsevier

Among primitive meteorites, CR chondrites have peculiar isotopic compositions, the origin of which is uncertain and may have involved contributions from primordial molecular cloud material or the chondrites’ formation and agglomeration late during the evolution of the protoplanetary disk. Here, we report a comprehensive textural and isotopic characterization of type I CR chondrules and provide new insights on their formation conditions. We find that two chondrule populations characterized by different sizes and oxygen isotopic compositions co-exist in CR chondrites. The typically larger, 16O-poor (-4‰) chondrules (type I-CR chondrules) appear to have formed late out of a CR reservoir already populated by typically smaller, 16O-rich (-4‰) chondrules (type I-CO chondrules). Before formation of type I-CR chondrules, the CR reservoir was likely dominated by CI-like dust, in line with the proximity of CR with CI chondrites for many isotopic ratios. The CR reservoir thus may have largely belonged to the continuum shown by other carbonaceous chondrites, although some isotopic ratios maintain some originality and suggest isotopic variation of CI-like dust in the outer disk. Combined with literature data, our data (i) demonstrates that recycling processes are responsible for the singular compositions of CR chondrites and their chondrules for isotopic systems with drastically different geochemical behaviors (O, Cr, Te) and (ii) support the homogeneous distribution of 26Al throughout the protoplanetary disk.