¹E.M.Hausrath et al. (>10)
Journal of Geophysical research (Planets) Link to Article [https://doi.org/10.1029/2022JE007433]
¹Department of Geoscience, University of Nevada, Las Vegas, Nevada, 89154 USA
Published by arrangement with John Wiley & Sons

Martian soils are critically important for understanding the history of Mars, past potentially habitable environments, returned samples, and future human exploration. This paper examines soil crusts on the floor of Jezero crater encountered during initial phases of the Mars 2020 mission. Soil surface crusts have been observed on Mars at other locations, starting with the two Viking Lander missions. Rover observations show that soil crusts are also common across the floor of Jezero crater, revealed in 45 of 101 locations where rover wheels disturbed the soil surface, 2 out of 7 helicopter flights that crossed the wheel tracks, and 4 of 8 abrasion/drilling sites. Most soils measured by the SuperCam laser-induced breakdown spectroscopy (LIBS) instrument show high hydrogen content at the surface, and fine-grained soils also show a visible/near infrared (VISIR) 1.9 µm H2O absorption feature. The Planetary Instrument for X-ray Lithochemistry (PIXL) and SuperCam observations suggest the presence of salts at the surface of rocks and soils. The correlation of S and Cl contents with H contents in SuperCam LIBS measurements suggests that the salts present are likely hydrated. On the “Naltsos” target, magnesium and sulfur are correlated in PIXL measurements, and Mg is tightly correlated with H at the SuperCam points, suggesting hydrated Mg-sulfates. Mars Environmental Dynamics Analyzer (MEDA) observations indicate possible frost events and potential changes in the hydration of Mg-sulfate salts. Jezero crater soil crusts may therefore form by salts that are hydrated by changes in relative humidity and frost events, cementing the soil surface together.

¹A.Udry et al. (>10)
Journal Geophysical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2022JE007440]
¹Department of Geosciences, University of Nevada Las Vegas, Las Vegas, NV, US
Published by arrangement with John Wiley & Sons

The Máaz formation consists of the first lithologies in Jezero crater analyzed by the Mars 2020 Perseverance rover. This formation, investigated from Sols (martian days) 1 to 201 and from Sols 343 to 382, overlies the Séítah formation (previously described as an olivine-rich cumulate) and was initially suggested to represent an igneous crater floor unit based on orbital analyses. Using SuperCam data, we conducted a detailed textural, chemical, and mineralogical analyses of the Máaz formation and the Content member of the Séítah formation. We conclude that the Máaz formation and the Content member are igneous and consist of different lava flows and/or possibly pyroclastic flows with complex textures, including vesicular and non-vesicular rocks with different grain sizes. The Máaz formation rocks exhibit some of the lowest Mg# (=molar 100×MgO/MgO+FeO) of all martian igneous rocks analyzed so far (including meteorites and surface rocks) and show similar basaltic to basaltic-andesitic compositions. Their mineralogy is dominated by Fe-rich augite to possibly ferrosilite and plagioclase, and minor phases such as Fe-Ti oxides and Si-rich phases. They show a broad diversity of both compositions and textures when compared to martian meteorites and other surface rocks. The different Máaz and Content lava or pyroclastic flows all originate from the same parental magma and/or the same magmatic system, but are not petrogenetically linked to the Séítah formation. The study of returned Máaz samples in Earth-based laboratories will help constrain the formation of these rocks, calibrate martian crater counting, and overall, improve our understanding of magmatism on Mars.

¹Iris Weber,¹Maximilian P. Reitze,¹Andreas Morlok,¹Aleksandra N. Stojic,¹Harald Hiesinger,¹Nico Schmedemann,¹Karin E. Bauch,¹Jan Hendrik Pasckert,²Jörn Helbert
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115683]
¹Institut für Planetologie (IfP), Westfälische Wilhelms-Universität, Wilhelm-Klemm-Str. 10, Münster 48149, Germany
²DLR, Institut für Planetenforschung, Rutherfordstr. 2, Berlin 12489, Germany
Copyright Elsevier

The behaviour of the Christiansen feature (CF) and the Reststrahlen bands (RBs) in mid-infrared (IR) reflectance spectra on various silicate mixtures as pressed pellets and powders was investigated in high-vacuum. In addition, the influence of micrometeorite bombardment simulated with an excimer laser was studied. The mixtures cover a wide range of possible hermean surface compositions and include the minerals olivine, pyroxene (enstatite and diopside), and plagioclase.

For the laser experiments, silicates were pressed into pellets and examined by reflectance infrared spectroscopy to identify changes caused by micrometeorite impacts as one tracer of space weathering on airless bodies such as Mercury. For comparison, measurements were also performed on loose powders with the same compositions under the same conditions. As a result, it can be shown that the RBs of olivine are rather affected by laser irradiation although SEM investigations show the destruction mainly of plagioclase, indicating that the RBs of plagioclase are masked by the “stronger” RBs of olivine and pyroxene. Furthermore, we found that the CF in mixtures with a plagioclase content of >50% does not shift significantly towards the CF of pyroxene or olivine. On the other hand, the CF of a mixture containing 50% olivine shifts significantly to shorter wavelengths when pyroxene or plagioclase are present in the mixture. Therefore, care is required when interpreting remote sensing data using the CF alone. We also found that the CF shifts to longer wavelengths in rough (regolithic) samples.

Our work demonstrates large dependencies of the CF and the RBs positions on the composition of the silicates as well as on the nature of the surface, which is important for space missions, e.g., data acquired by the MErcury Radiometer and Thermal Infrared Spectrometer (MERTIS) experiment onboard BepiColombo.

¹Adriana Pisarčíková,¹Pavol Matlovič,¹Juraj Tóth,²Stefan Loehle,³Ludovic Ferrière,²David Leiser,²Felix Grigat,⁴Jérémie Vaubaillon
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115682]
¹Faculty of Mathematics, Physics and Informatics, Comenius University in Bratislava, Slovakia
²High Enthalpy Flow Diagnostics Group, Institute of Space Systems, University of Stuttgart, Pfaffenwaldring 29, Stuttgart, 70569, Germany
³Natural History Museum Vienna, Burgring 7, Vienna, 1010, Austria
⁴IMCCE, Observatoire de Paris, PSL, 77 Av Denfert Rochereau, Paris, 75014, France
Copyright Elsevier

Fragments of small solar system bodies entering Earth’s atmosphere have possibly been important contributors of organic compounds to the early Earth. The cyano radical (CN) emission from meteors is considered as potentially one of the most suitable markers of organic compounds in meteoroids, however, its detection in meteor spectra has been thus far unsuccessful. With the aim to improve our abilities to identify CN emission in meteor observations and use its spectral features to characterize the composition of incoming asteroidal meteoroids, we present a detailed analysis of CN emission from high-resolution spectra of 22 laboratory simulated meteors including ordinary, carbonaceous, and enstatite chondrites, as well as a large diversity of achondrites (i.e., ureilite, aubrite, lunar, martian, howardite, eucrite, and diogenite), mesosiderite, and iron meteorites. We describe the variations of CN emission from different classes of asteroidal meteor analogues, its correlation and time evolution relative to other major meteoroid components. We demonstrate that CN can be used as a diagnostic spectral feature of carbonaceous and carbon-rich meteoroids, while most ordinary chondrites show no signs of CN. Our results point out strong correlation between CN and H emission and suggest both volatile features are suitable to trace contents of organic matter and water molecules present within meteoroids. For the application in lower resolution meteor observations, we demonstrate that CN can be best recognized in the early stages of ablation and for carbon-rich materials by measuring relative intensity ratio of CN band peak to the nearby Fe I-4 lines.

¹Baum, Sebastian et al. (>10)
Physics of the Dark Universe 41, 101245 Open Access Link to Article [DOI 10.1016/j.dark.2023.101245]
¹Stanford Institute for Theoretical Physics, Department of Physics, Stanford University, Stanford, 94305, CA, United States

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

¹K. Righter,²A. Boujibar,³M. Humayun,³S. Yang,^4,5R. Rowland II,⁵K. Pando
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2023.06.014]
¹NASA JSC, Mailcode XI2, 2101 NASA Pkwy, Houston, TX 77058 USA
²Western Washington University, Geology Department ES – 240, Department of Physics and Astronomy, MS 9080, 516, High Street, Bellingham, WA, 98225 USA
³National High Magnetic Field Laboratory and Department of Earth, Ocean & Atmospheric Science, Florida State University, Tallahassee, FL 32310, USA
⁴Los Alamos National Laboratory, Mail Stop P952, Los Alamos, NM 87545, USA
⁵Jacobs JETS Contract, NASA JSC, Houston, TX 77058 USA
Copyright Elsevier

Understanding siderophile element partitioning between metal and silicate melts under diverse conditions can be used to place important constraints on the materials and conditions of planetary accretion and core formation, as well as post core formation processes. However, the effects of Si on the partitioning and activity coefficients for these elements are not well known, despite Si likely being one of the dominant light elements in Earth’s core. To address this gap in understanding, we have undertaken a systematic study of the highly siderophile elements Re, Pt, Os, and Ru, and the refractory lithophile elements Nb, Ta and Ti at 1600 °C and 1 GPa, to derive epsilon interaction parameters for these elements in FeSi metallic liquids. Positive epsilon interaction parameters were measured for Nb, Ta, Ti, Ru, Re, Pt, and Os, indicating that dissolved Si in Fe liquids causes a decrease in their metal/silicate partition coefficients (or ‘silicophobic’ behavior). Furthermore,
>
which means Si causes a larger decrease in D(metal/silicate) and the chalcophile behavior expected from some elements will be completely masked by the presence of Si in a metallic liquid. The new parameters are used to update an activity model that now includes 36 siderophile elements in Fe-Ni-Si-S-C liquids (26 trace elements). Systematic assessment of these 26 elements shows which have the strongest affinity for Si, C, and S, and also how activity coefficients for these elements would vary during accretion and core formation in Earth, Mars, and Mercury of widely differing fO2 and core compositional conditions. The activity model is combined with new partitioning expressions for Mo, W, Cr, Re Ru, Pt, and Os and applied to aspects of post core formation mantle geochemistry of Earth, Mars, and Mercury. Our updated expressions show that the BSE Mo/W ratio can easily be achieved with metal/silicate partitioning during growth of the Earth, whereas Re, Os and Ru become lower than and highly fractionated compared with BSE values during core formation and accretion, and thus nearly 99% of their BSE abundances are likely contributed by late accretion. Ru isotopes should be a very good indicator of the source material for the late accretion. The high Pt/Os and Re/Os developed in a deepening magma ocean during the growth of the Earth, indicates 186Os and 187Os isotopes could be coupled if this ancient material remained isolated and subsequently became entrained in mantle plumes and measured in surficial lavas. The extent to which this occurred will be limited by the low Os content of this ancient material, thus requiring mixing as a major component in plume sources. Martian mantle Hf/W ratio stays low during accretion and core formation modelling, suggesting that W isotope anomalies are more likely due to solid/liquid silicate fractionation than to core formation. Finally, Ti contents measured by MESSENGER at Mercury’s surface can be explained by segregation of either a metallic core (IW-6 to -7.5) or metallic core + sulfide (IW-3.5 to -7) followed by mantle melting.

¹Frank Postberg et al. (>10)
Nature 618, 489–493 Open Access Link to Article [DOI https://doi.org/10.1038/s41586-023-05987-9]
¹Institut für Geologische Wissenschaften, Freie Universität Berlin, Berlin, Germany

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

¹Emily M. Chiappe,¹Richard D. Ash,¹Richard J. Walker
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2023.06.009]
¹Department of Geology, University of Maryland, College Park, Maryland, 20742, USA
Copyright Elsevier

Chemical and isotopic data were obtained for ten iron meteorites classified as members of the IIIE group. Nine of the IIIE irons exhibit broadly similar bulk siderophile element characteristics. Modeling of highly siderophile element abundances suggests that they can be related to one another through simple crystal-liquid fractionation of a parent melt. Our preferred model suggests initial S, P, and C concentrations of approximately 12 wt.%, 0.8 wt.%, and 0.08 wt.%, respectively. The modeled IIIE parent melt composition is ∼4 times more enriched in highly siderophile elements than a non-carbonaceous (NC) chondrite-like parent body, suggesting a core comprising ∼22% of the mass of the parent body. Although chemically distinct from the other IIIE irons, formation of the anomalous IIIE iron Aletai can potentially be accounted for under the conditions of this model through the non-equilibrium mixing of an evolved liquid and early formed solid. Cosmic ray exposure-corrected nucleosynthetic Mo, Ru, and W isotopic compositions of four of the bona fide IIIE irons and Aletai indicate that they originated from the non-carbonaceous (NC) isotopic domain. Tungsten-182 isotopic data for the IIIE irons and Aletai yield similar model metal-silicate segregation ages of 1.6 ± 0.8 Myr and 1.2 ± 0.8 Myr, respectively, after calcium aluminum-rich inclusion (CAI) formation. These ages are consistent with those reported for other NC-type iron meteorite parent bodies. The IIIE irons are chemically and isotopically similar to the much larger IIIAB group. Despite some textural, mineralogical, and chemical differences, such as higher C content, the new results suggest they may have originated from a different crystallization sequence on the same or closely-related parent body.

¹Sarah S. Zeichner,^1,2Laura Chimiak,³Jamie E. Elsila,¹Alex L. Sessions,³Jason P. Dworkin,³José C. Aponte,¹John M. Eiler
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2023.06.010]
¹Division of Geological & Planetary Sciences, California Institute of Technology, Pasadena, CA 90025, USA
²Department of Geological Sciences, UCB 399, University of Colorado, Boulder, CO 80309, USA
³Solar System Exploration Division, Code 691, NASA Goddard Space Flight Center, Greenbelt, MD, 20771. USA
Copyright Elsevier

The Murchison meteorite is a well-studied carbonaceous chondrite with relatively high concentrations of amino acids thought to be endogenous to the meteorite, in part because they are characterized by carbon isotope (δ13C) values higher than those typical of terrestrial amino acids. Past studies have proposed that extraterrestrial amino acids in the Murchison meteorite could have formed by Strecker synthesis (for α-amino acids), Michael addition (for β-amino acids), or reductive amination, but a lack of constraints have prevented confident discrimination among these possibilities, or assignment of specific formation pathways to each of several specific amino acids. Position-specific carbon isotope analysis differentiates amongst these mechanisms by relating molecular sites to isotopically distinct carbon sources and by constraining isotope effects associated with elementary chemical reactions. Prior measurements of the position-specific carbon isotopic composition of α-alanine from the Murchison CM chondrite demonstrated that alanine’s high δ13CVPDB value is attributable to the amine carbon (δ13CVPDB = +142±20‰), consistent with Strecker synthesis drawing on 13C-rich carbonyl groups in precursors (L. Chimiak et al., Geochim. Cosmochim. Acta 292, 188–202, 2021). Here, we measured the δ13C composition of fragment ions generated by electron impact ionization of derivatized ⍺-alanine, β-alanine, and aspartic acid from Murchison via gas chromatography-Fourier transform mass spectrometry. α-Alanine’s amine carbon yielded δ13CVPDB = +109±21‰, which is consistent with the previously measured value and with formation from 13C-rich precursors. β-Alanine’s amine carbon presents a lower δ13CVPDB = +33±24‰, which supports formation from 13C-rich precursors but potentially via a Michael addition mechanism rather than Strecker synthesis. Aspartic acid’s amine carbon has δ13CVPDB= –14±5‰, suggesting synthesis from precursors distinct from those that generated the alanine isomers. These measurements indicate that Murchison amino acids are a mixture of compounds made from different synthesis mechanisms, though some subsets likely drew on the same substrates; this conclusion highlights the complexity of extraterrestrial organic synthesis networks and the potential of emerging methods of isotope ratio analysis to elucidate the details of those networks.

^1,2Aryavart Anand,²Klaus Mezger
Chemie der Erde/Geochemistry (in Press) Link to Article [https://doi.org/10.1016/j.chemer.2023.126004]
¹Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
²Institut für Geologie, Universität Bern, Baltzerstrasse 1+3, 3012 Bern, Switzerland
Copyright Elsevier

Age constraints on early solar system processes and events can be derived from meteorites and their components using different radioisotope systems. Due to the short time interval from the first formation of solids in the solar nebula to the accretion and differentiation of planetesimals and some planets, a high temporal resolution of the chronometers is essential and can be obtained in most cases only with short-lived isotope systems, particularly the decay schemes 26Al-26Mg, 182Hf-182W and 53Mn-53Cr. These chronometers provide highly resolved time constrains for the formation of the first solids (Ca-Al-rich inclusions or CAIs), chondrules, planetary cores, for the accretion and differentiation of planetesimals and hydrous/thermal alteration. Formation of Ca-Al-rich inclusions was restricted to the inner solar system and to a short time interval of ≪1 Ma, and marks the “beginning of the solar system”. It was immediately followed by planetesimal formation. The oldest planetesimals accreted within a few 105 a after the formation of CAIs. The accretion of early formed planetesimals and their subsequent differentiation into a metallic core and a silicate mantle was a continuous process that occurred at different times in different locations of the solar nebula and extended over a time interval of at least ~4 Ma. During this time interval the accretion process may have changed from planetesimal formation via streaming instability to pebble accretion. The earliest formed bodies that still needed to settle into stable orbits could have created bow shocks in the adjacent regions still composed of dust and gas which resulted in the formation of silicate chondrules in a narrow time interval from 1.8 to 3 Ma. The chondrule forming interval was immediately followed by the accretion of the chondrite parent bodies, which did not differentiate due to their late accretion when most of the heat producing 26Al had already decayed. Thus, the chondrite parent bodies are a second generation of planetesimals, but chemically they are the most primitive material preserved from the early solar system. Aqueous alteration of volatile rich planetesimals peaked at ca. 3.5 Ma and coincided with metamorphism recorded in ordinary chondrite parent bodies. The compilation of ages from different meteorites and their components demonstrates that similar accretion and differentiation processes do not follow an identical time line from dust to planetesimal formation and they do not correlate with the location in the disk. The accretion of matter into planetesimals was a local phenomenon with stochastic spatial distribution. The spatial distribution of accretion processes operating in the early solar system appears to be similar to those in some directly observable nascent exo-planetary systems.