¹A. Deanne Rogers,²Steven W. Ruff,³Michael D. Smith
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115687]
¹Stony Brook University, Stony Brook, NY, USA
²Arizona State University, Tempe, AZ, USA
³NASA Goddard Space Flight Center, Greenbelt, MD, USA
Copyright Elsevier

It has been hypothesized that the dust component of the Martian surface is globally homogeneous, based on chemical similarity between landing sites and spectral similarity from select areas within bright regions. We tested that hypothesis by producing the first near-global data set of surface spectral emissivity (excluding polar regions) across the ~233–508 and 825–1650 cm−1 (~20–50 and 6–12 μm) spectral ranges from Mars Global Surveyor Thermal Emission Spectrometer data and using various data reduction techniques to search for any spectral heterogeneity in bright regions that might be present. We found no unequivocal evidence for spectral heterogeneity, supporting the hypothesis that dust is globally homogenized. The global emissivity product permits new spectral parameter maps and preliminary assessments of atmosphere-regolith interactions. We produced the first map of the Christiansen feature (CF) and show that, unlike on the Moon, where CF is a proxy for bulk silica content, CF position on Mars is primarily associated with dust cover. We produced an updated map of the 1630 cm−1 emissivity peak that arises from bound H2O in fine-particulate material and show that the peak is nearly ubiquitous across the Martian surface, including in dark regions with relatively low dust cover. This is attributed to minor amounts of dust disproportionally contributing to the spectral signal in the ~1630 cm−1 region. We show that regions within the equatorial dust deposits with higher annual modeled frequency of nighttime CO2 frosts are more likely to have lower emissivity in the ~1350-1400 cm−1 region, consistent with a higher fraction of unconsolidated dust. This provides the first spectral evidence for a previously hypothesized regolith gardening process via a diurnal CO2 cycle, representing an important surface-atmosphere interaction that may contribute to near-surface porosity and affect diffusive exchange of H2O between atmosphere and hydrated solids (ice, minerals) in the regolith.

¹Yevgeniy P. Gurov,¹Vitaliy V. Permiakov
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13999]
¹Institute of Geological Sciences, National Academy of Sciences of Ukraine, Kyiv, Ukraine
Published by arrangement with John Wiley & Sons

Metallic microspheres have been found in rocks from the Onaping Formation of the Sudbury impact structure, Canada. Microspherules are common in contact breccias, the lowest part of the Dowling Member, and rare microspherules have been found in the upper sequences of the Dowling Member. Separate microspherules are dispersed in the breccia matrix and do not form clusters. The sizes of the microspheres range from 5 to 30 μm; most commonly, they are 8–15 μm in size. The microspherules have a regular spherical shape, and in some cases show concentric zonal structures. The microspherules consist mostly of the refractory elements Cr, Co, Fe, Mo, W, and Ti, with a predominant Ni content of 40–75 wt%. The formation of the Sudbury metal microspherules by condensation in a high-temperature plume is suggested by their spherical shape, concentric-zoned structure, uniform composition, and distribution in fallback breccias of the crater-fill Onaping Formation. The content of the most refractory W in the composition of the microspheres indicates early condensation. A decrease in the content of W and an increase in the content of Ni in the microspheres of the upper layers relative to the content of these elements in the earliest microspheres of the contact layers indicate that they could have formed by fractional condensation during the expansion and cooling of the impact vapor plume. As source material, a combination of target rocks with high nickel content with a chondritic impactor is suggested.

¹Naotaka Tomioka et al. (>10)
Nature Astronomy 7, 669–677 Open Access Link to Article [DOI https://doi.org/10.1038/s41550-023-01947-5]
¹Kochi Institute for Core Sample Research, X-star, Japan Agency for Marine-Earth Science and Technology, Nankoku, Japan

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¹Alexander Rogaski,^1,2Gokce K. Ustunisik,³Shuying Yang,³Munir Humayun,⁴Kevin Righter,⁵Jeff A. Berger,⁶Nicholas DiFrancesco
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14000]
¹Department of Geology and Geological Engineering, South Dakota School of Mines and Technology, Rapid City, South Dakota, USA
²Department of Earth and Planetary Sciences, American Museum of Natural History, New York, New York, USA
³National High Magnetic Field Laboratory, Department of Earth, Ocean and Atmospheric Science, Florida State University, Tallahassee, Florida, USA
⁴National Aeronautics and Space Administration, Lyndon B. Johnson Space Center, Houston, Texas, USA
⁵Jacobs JETSII, NASA Johnson Space Center, Houston, Texas, USA
⁶Department of Geology, University at Buffalo, Buffalo, New York, USA
Published by arrangement with John Wiley & Sons

The surface of Mars is enriched in Cl and S which is linked to volcanic activity and degassing. Similarly, elevated Ge and Zn levels in Gale crater sedimentary bedrock indicate a magmatic source for these elements. To constrain the relative effects of Cl and S on the outgassing of these trace metals and chemical characteristics of primary magmatic vapor deposits incorporated to Martian surface, we conducted a set of degassing and fumarolic alteration experiments. Ge is found to be more volatile than Zn in all experiments. In S-bearing runs, the loss of Ge and Zn was less than any other experiments. In Cl-only runs, degassing of Zn was more than twice that of Ge within the first 10 min and percent loss increased for both elements with increasing time. In Cl + S runs, S-induced reduction of GeO2 and ZnO to metallic Ge and Zn switches the preference of chloride formation from Zn to Ge. Up to 90% of Ge and Zn loss in the 1-h no volatile-added (NVA) experiments might be due to the small amounts of Cl contamination in NVA mixes via other oxides used for synthesis. Alteration experiments show different phases between 1-h and 24-/72-h runs. In 1-h runs, anhydrite and langbeinite dominate while in 24-/72-h runs halite and sylvite dominate the condensate assemblages. S-bearing phases form as the intermediate products of fumarolic deposition, while chlorides are common when the system is allowed to cool gradually. One-hour exposure was sufficient to form alteration phases and vapor deposits such as NaCl, KCl, CaSO4, and langbeinites on the Martian analog minerals. These salts were identified in Martian meteorites and in situ measurements. Our results provide evidence that volcanic degassing along with fumarolic alteration could be a potential source for the enrichment and varying abundances of Cl, S, Fe, Zn, Ge in Martian surface, as well as a cause for Ge depletion in shergottites.

¹K.E. Bristol,^1,2A.V. Smirnov,³E.J. Piispa,⁴M.R. Ramirez Navas,⁵A. Kosterov,^6,7E.V. Kulakov
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115684]
¹Department of Geological and Mining Engineering and Sciences, Michigan Technological University, Houghton, MI, USA
²Department of Physics, Michigan Technological University, Houghton, MI, USA
³Institute of Earth Sciences, University of Iceland, Reykjavík, Iceland
⁴Instituto Geografico Militar, Quito, Ecuador
⁵Department of Earth Physics, Saint Petersburg University, Saint Petersburg, Russia
⁶Centre for Earth Evolution and Dynamics (CEED), University of Oslo, Norway
⁷Northland Pioneer College, Show Low, AZ, USA
Copyright Elsevier

We investigated the magnetic properties of Ecuador’s first reported meteorite fall (March 23, 2008), the Daule ordinary chondrite (L5, S4, W0) using thermomagnetic analyses at high and cryogenic temperatures, analyses of magnetic hysteresis and first-order reversal curves, and thermal and alternating field (AF) demagnetization of natural remanent magnetization (NRM). The mineralogical and chemical composition of Daule was examined using scanning electron microscopy with energy-dispersive x-ray spectroscopy. Most methods indicate that the magnetic properties of Daule are dominated by multidomain FeNi alloys (kamacite) with Ni content varying between ~4% and ~ 17%. However, backfield demagnetization (BFD) analyses revealed the presence of high-coercivity tetrataenite that survived shock metamorphism. The differential survival of tetrataenite at the millimeter scale indicates heterogeneity of the impact-related temperature and pressure fields within the Daule meteorite. BFD curves may serve as an efficient tool for identifying minor amounts of tetrataenite that otherwise cannot be discerned from the signal from magnetically-soft FeNi mineral phases by methods based on induced magnetization. Thermal demagnetization experiments unveiled the presence of a well-defined characteristic component of NRM, which remains resistant to AF demagnetization. We interpret this component as a pre-impact thermochemical remanence carried by tetrataenite and acquired during the thermal metamorphism of the parent body. At cryogenic temperatures, the magnetic properties of Daule are dominated by low-Mg magnesiochromite with the Curie temperature at 60–70 K.

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

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