Far‐UV Observations of Lunar Rayed Craters with LRO‐LAMP

1,2B. D. Byron,1,2K. D. Retherford,2T. K. Greathouse,2D. Wyrick,3J. T. S. Cahill,4A. R. Hendrix,1,2U. Raut,3K. E. Mandt,3B. W. Denevi
Journal of Geophysical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2019JE006269]
1Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, TX, USA
2Space Science and Engineering Department, Southwest Research Institute, San Antonio, TX, USA
3The Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
4Planetary Science Institute, Tucson, AZ, USA
Published by arrangement with John Wiley & Son

Using data from the Lunar Reconnaissance Orbiter (LRO) Lyman Alpha Mapping Project (LAMP), we investigate the spectral properties of rayed craters in the far‐ultraviolet (FUV). Because LAMP is sensitive to the uppermost layer of the lunar surface and regolith grains, it is ideal for characterizing regolith maturity and space weathering products such as submicroscopic iron. We find that crater rays from a survey of the largest Copernican‐age craters have high Off‐band (155–190 nm)/On‐band (130–155 nm) albedo (Off/On) LAMP product ratios, consistent with immature regolith and low amounts of submicroscopic iron. The Off/On ratio of the highlands crater rays decreases linearly over time (0.095 per 100 My), and we use this trend to estimate the age of Jackson crater (~152 My). Some large young highlands craters (e.g., Tycho, Jackson, Giordano Bruno, and Necho) display lower ratio halos around the crater cavity, at regions where previous studies have suggested abundant impact melt exists. The lower Off/On ratio is likely due to the increased glass component of the regolith at these highlands regions, which would act to increase absorption at Off‐band wavelengths. We also find that ejecta blankets from large maria craters (e.g., Copernicus and Aristillus) have a similar Off/On ratio to the mature background highlands. This supports previous findings that determined that the rays from these craters are composed of highlands material excavated from beneath the maria and subsequently weathered to maturity.

 

Olivine‐Carbonate Mineralogy of the Jezero Crater Region

1A. J. Brown,2C. E. Viviano,3T. A. Goudge
Journal of Geophysical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2019JE006011]
1Plancius Research, Severna Park, MD, USA
2Johns Hopkins Applied Physics Laboratory, Laurel, MD, USA
3Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, TX, USAPublished by arrangement with John Wiley & Sons

A well‐preserved, ancient delta deposit, in combination with ample exposures of carbonate outcrops, makes Jezero Crater in Nili Fossae a compelling astrobiological site. We use Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) observations to characterize the surface mineralogy of the crater and surrounding watershed. Previous studies have documented the occurrence of olivine and carbonates in the Nili Fossae region. We focus on correlations between these two well‐studied lithologies in the Jezero crater watershed. We map the position and shape of the olivine 1 μm absorption band and find that carbonates are found in association with olivine which displays a 1 μm band shifted to long wavelengths. We then use Thermal Emission Imaging Spectrometer (THEMIS) coverage of Nili Fossae and perform tests to investigate whether the long wavelength shifted (redshifted) olivine signature is correlated with high thermal inertia outcrops. We find that there is no consistent correlation between thermal inertia and the unique olivine signature. We discuss a range of formation scenarios for the olivine and carbonate associations, including the possibility that these lithologies are products of serpentinization reactions on early Mars. These lithologies provide an opportunity for deepening our understanding of early Mars and, given their antiquity, may provide a framework to study the timing of valley networks and the thermal history of the Martian crust and interior from the early Noachian to today.

Supply of phosphate to early Earth by photogeochemistry after meteoritic weathering

1Dougal J. Ritson,2,3Stephen J. Mojzsis,1John. D. Sutherland
Nature Geoscience (in Press) Link to Article [DOI https://doi.org/10.1038/s41561-020-0556-7]
1MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, UK
2Department of Geological Sciences, University of Colorado, Boulder, CO, USA
Stephen J. Mojzsis
3Institute for Geological and Geochemical Research, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, Budapest, Hungary
Stephen J. Mojzsis

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Distinct oxygen isotope compositions of the Earth and Moon

1Erick J. Cano,1Zachary D. Sharp,2Charles K. Shearer
Nature Geoscience (in Press) Link to Article [DOI https://doi.org/10.1038/s41561-020-0550-0]
1Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM, USA
2Institute of Meteoritics, University of New Mexico, Albuquerque, NM, USA

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Utilization of urea as an accessible superplasticizer on the moon for lunar geopolymer mixtures

1Shima Pilehvar,2Marlies Arnhof,3Ramón Pamies,4Luca Valentini,1Anna-Lena Kjøniksen
Journal of Cleaner Production 247, 119177 Link to Article [https://doi.org/10.1016/j.jclepro.2019.119177]
1Faculty of Engineering, Østfold University College, P.O. Box 700, 1757, Halden, Norway
2Advanced Concepts Team, ESA European Space Research and Technology Centre, Keplerlaan 1, TEC-SF, 2201AZ, Noordwijk, Netherlands
3Department of Materials Engineering and Manufacturing, Technical University of Cartagena, Cartagena, Murcia, Spain
4Department of Geosciences, University of Padua, 35131, Padua, Italy

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53Mn and 60Fe in iron meteorites—New data, model calculations

1Ingo Leya et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13466]
1Physics Institute, University of Bern, Sidlerstrasse 5, CH‐3012 Bern, Switzerland
Published by arrangement with John Wiley & Sons

We measured specific activities of the long‐lived cosmogenic radionuclides 60Fe in 28 iron meteorites and 53Mn in 41 iron meteorites. Accelerator mass spectrometry was applied at the 14 MV Heavy Ion Accelerator Facility at ANU Canberra for all samples except for two which were measured at the Maier‐Leibnitz Laboratory, Munich. For the large iron meteorite Twannberg (IIG), we measured six samples for 53Mn. This work doubles the number of existing individual 60Fe data and quadruples the number of iron meteorites studied for 60Fe. We also significantly extended the entire 53Mn database for iron meteorites. The 53Mn data for the iron meteorite Twannberg vary by more than a factor of 30, indicating a significant shielding dependency. In addition, we performed new model calculations for the production of 60Fe and 53Mn in iron meteorites. While the new model is based on the same particle spectra as the earlier model, we no longer use experimental cross sections but instead use cross sections that were calculated using the latest version of the nuclear model code INCL. The new model predictions differ substantially from results obtained with the previous model. Predictions for the 60Fe activity concentrations are about a factor of 2 higher, for 53Mn, they are ~30% lower, compared to the earlier model, which gives now a better agreement with the experimental data.

Distinguishing relative aqueous alteration and heating among CM chondrites with IR spectroscopy

1R.D.Hanna,2V.E.Hamilton,3C.W.Haberle,4,5A.J.King,6N.M.Abreu,7,8J.M.Friedrich
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2020.113760]
1Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78712, USA
2Department of Space Studies, Southwest Research Institute, Boulder, CO 80302, USA
3School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA
4School of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
5Planetary Materials Group, Department of Earth Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK
6Earth Science Program, Pennsylvania State University, Du Bois, PA 15801, USA
7Department of Chemistry, Fordham University, Bronx, NY 10458, USA
8Department of Earth and Planetary Sciences, American Museum of Natural History, New York, NY 10024, USA
Copyright Elsevier

Using infrared (IR) spectroscopy of thin sections, we characterize the relative degree of aqueous alteration and subsequent heating of a suite of CM chondrites to document spectral indicators of these processes that can contextualize observations of carbonaceous asteroids. We find that the progressive aqueous alteration of CMs manifests in two spectral regions. The low-wavenumber region (1200–400 cm−1; 8–25 μm) records the increasing proportion of MgFe phyllosilicates relative to anhydrous silicates as aqueous alteration proceeds, with a highly correlated shift of the Christiansen feature (CF) to lower wavenumber and the SiO bending band minimum to higher wavenumber, and an increase in depth of the Mg-OH band (~625 cm−1). The strongest correlation (R2 = 0.90) with petrologic subtype is the distance between the CF and SiO stretching band minimum, which predicts the petrologic subtype of the sample to within 0.1. The high-wavenumber region (4000–2500 cm−1, ≤3.33 μm) probes the variation in abundance and composition of MgFe serpentine and tochilinite among the altered CMs. All moderately to highly altered CMs (≤2.3) have an OH/H2O (‘3 μm’) band emission maximum of 3690 cm−1 (2.71 μm) indicative of Mg-bearing serpentine, and mildly aqueously altered CMs (≥ 2.5) have a wider band with a complex shape that results from contributions of Fe-bearing serpentine and tochilinite. Among weakly heated CMs (Stage II; 300–500 °C), the low-wavenumber region exhibits spectral features resulting from the dehydration and dehydroxylation of phyllosilicates that include broadening of the SiO stretching band and a shift of its minimum to lower wavenumber, and the disappearance of the Mg-OH band. The location of the SiO bending band minimum appears to be unaffected by mild heating. Extensively heated CMs (Stage III+; >500 °C) have a low-wavenumber region dominated by the spectral features of secondary, Fe-bearing olivine and low-Ca pyroxene and thus are readily distinguished from unheated and mildly heated CMs. The OH/H2O band of all heated CMs is broad and rounded with an emission peak at higher wavenumbers (≤3636 cm−1; ≥2.75 μm) than in unheated CMs. However, spectral and petrographic evidence suggests that our heated CMs have been compromised by terrestrial rehydration. Our study confirms that thermal metamorphism effects are concentrated within the matrix and suggests that the matrix of the CM WIS 91600 had a CI-like mineralogy prior to heating.