¹Sohei Wada,¹Noriyuki Kawasaki,²Changkun Park,^1,3Hisayoshi Yurimoto
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2020.08.004]
¹Department of Natural History Sciences, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan
²Division of Earth-System Sciences, Korea Polar Research Institute, Incheon 21990, Republic of Korea
³Isotope Imaging Laboratory, Creative Research Institution, Hokkaido University, Sapporo 001-0021, Japan
Copyright Elsevier

Fine-grained Ca-Al-rich inclusions (FGIs) in CV chondrites are suggested to be condensates from the solar nebular gas and thus captured O-isotopes from the gas. We conducted a combined study of petrographic observations and in situ O-isotope analysis using secondary ion mass spectrometry for an FGI, named HKD01, from the reduced CV chondrite Northwest Africa 8613. HKD01 has an irregular shape and petrographically three-layered structures: a hibonite-rich core, a spinel-rich core, and a mantle. Each petrographic domain contains melilite, hibonite, and spinel with variable proportions of those minerals. The O-isotopic compositions of the constituent minerals plotted along the slope-1 line on an O three-isotope diagram ranged between Δ¹⁷O ∼ −23‰ and 1‰. Hibonite and spinel are uniformly ¹⁶O-rich (Δ¹⁷O = −23‰) irrespective of their occurrences, while melilite crystals exhibit wide O-isotope variations ranging between Δ¹⁷O ∼ −23‰ and 1‰. The O-isotopic composition in a melilite crystal changes abruptly within ∼2 µm, indicating that disturbances of O-isotopes in melilite after condensation are less than ∼2 µm. Because the melilite in the FGI typically has grain sizes of 5−10 µm, the abrupt change of O-isotopic composition demonstrates that melilite crystals in the FGI preserve the O-isotopic composition of the nebular gas from which they condensed. In the mantle, aggregates of melilite crystals, having relatively large grain sizes (10−25 µm) and oscillatory chemical zoning, exhibit ¹⁶O-poor compositions with small variations ranging between Δ¹⁷O ∼ −4 and 1‰. Among them, a large melilite crystal (∼20 µm) with homogeneously ¹⁶O-poor composition (Δ¹⁷O ∼ 0‰) across the single crystal was found. The coexistence of ¹⁶O-poor and ¹⁶O-rich melilite crystals without O-isotope disturbances in the FGI reveals that ¹⁶O-poor (Δ¹⁷O ∼ 0‰) nebular gas existed in the formation region of the FGI HKD01 in addition to ¹⁶O-rich (Δ¹⁷O ∼ –23‰) nebular gas.

^1,2Druce, M.,^1,2Stirling, C.H.,³Rolison, J.M.
Geostandards and Geoanalytical Research (in Press) Link to Article [DOI: 10.1111/ggr.12341]
¹Department of Chemistry, University of Otago, PO Box 56, Dunedin, New Zealand
²Centre for Trace Element Analysis, University of Otago, PO Box 56, Dunedin, New Zealand
³Nuclear and Chemical Sciences Division, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94551-0808, United States

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

¹Ted L.Roush
Icarsu (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2020.114056]
¹Space Sciences Division, NASA Ames Research Center, Planetary Systems Branch, MS 245-3, Moffett Field, CA 94035-1000, United States of America
Copyright Elsevier

The visible, near-, and mid-infrared (≈0.4–6 μm) imaginary indices of refraction (k) are estimated from reflectance spectra for three carbonates germane to martian and terrestrial studies. The resulting values are combined with previous data at longer wavelengths and a subtractive Kramers-Konig analysis is used to estimate the real indices of refraction (n) as a function of wavelength. This process is iterated until neither the n or k vary significantly. The results provide estimated complex refractive indices spanning the ≈0.4–400 μm. The estimated visible, near-, and mid-infrared carbonate complex refractive indices are broadly consistent with previous studies, but extend the wavelength coverage and improve the spectral resolution for these materials.

¹Gordon M.Gartrelle,^1,2Paul S.Hardersen,^1,3Matthew R.M.Izawa,^1,4Matthew C.Nowinski
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2020.114043]
¹University of North Dakota, Grand Forks, ND, USA
²Trouvaille LLC, Tucson, AZ, USA
³Institute of Planetary Materials, Okayama University, Misasa, Japan
⁴The Boeing Company, Washington, DC, USA
Copyright Elsevier

D-type asteroids are a prime example of the many dark, low-albedo asteroids which do not reflect sufficient light to reveal detectable mineral absorptions. While D-type asteroids are relatively rare in the inner solar system and the main asteroid belt, they are dominant among the Jovian Trojans. In this study, we have applied Shkuratov radiative transfer modeling to laboratory spectra of meteorites for which mineral abundances have been measured using X-ray diffraction (XRD) and Rietveld refinement. The general agreement of radiative transfer and XRD estimates of mineral abundances demonstrates the applicability of the radiative transfer approach to featureless, low-albedo spectra. Shkuratov modeling was then applied to new spectral observations of D-type asteroids, along with numerous previously published spectra. The surface mineral abundances of 81 D-type objects, including NASA’s Lucy Mission target (21900) Orus, were modeled using assemblages that are plausible based on meteorite analogues. Modeling results reveal D-types are composed of: low-iron olivine; magnesium saponite-dominant phyllosilicates; opaques such as pyrrhotite and tholin; as well as traces of water-ice and other constituents. Subtle compositional differences in model mineralogies exist between Trojan and non-Trojan D-types as well as between L4 and L5 Trojans suggesting differing formational as well as evolutional conditions have affected these bodies.

¹S. Potin,¹P. Beck,¹L. Bonal,¹B. Schmitt,²A. Garenne,³F. Moynier,⁴A. Agranier,^5,6P. Schmitt‐Kopplin,⁷A. K. Malik,¹E. Quirico
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13540]
¹Institut de Planétologie et d’Astrophysique de Grenoble IPAG, Université Grenoble Alpes, CNRS, 414 rue de la Piscine, 38400 Saint‐Martin d’Hères, France
²Nuclear and Chemical Sciences Division, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California, 94550 USA
³Institut de Physique du Globe de Paris, Université de Paris, CNRS, 1 rue Jussieu, 75005 Paris, France
⁴Laboratoire Géosciences Océan, UMR/CNRS 6538, IUEM, Université de Bretagne Occidentale, Technopôle Brest‐Iroise, Rue Dumont d’Urville, 29280 Plouzané, France
⁵Helmholtz Zentrum Muenchen, Research Unit Environmental Simulation (EUS) Ingolstaedter Landstrasse 1, 85764 Neuherberg, Germany
⁶Lehrstuhl für Analytische Lebensmittechemie, Technische Universität München, Maximus‐von‐Imhof‐Forum 2, 85354 Freising, Germany
⁷Department of Chemistry, Punjabi University, Patiala, 147 002 Punjab, India
Published by arrangement with John Wiley & Sons

We present here several laboratory analyses performed on the freshly fallen Mukundpura CM chondrite. Results of infrared transmission spectroscopy, thermogravimetry analysis, and reflectance spectroscopy show that Mukundpura is mainly composed of phyllosilicates. The rare earth trace elements composition and ultrahigh‐resolution mass spectrometry of the soluble organic matter give results consistent with CM chondrites. Finally, Raman spectroscopy shows no signs of thermal alteration of the meteorite. All the results agree that Mukundpura has been strongly altered by water on its parent body. Comparison of the results obtained on the meteorite with those of other chondrites of known petrologic types leads to the conclusion that Mukundpura is similar to CM1 chondrites, which differ from its original classification as a CM2.

¹Kennington, A.R.L. et al. (>10)
Physical Review Letters 124, 252702 Link to Article [DOI: 10.1103/PhysRevLett.124.252702]
¹Department of Physics, University of Surrey, Guildford, GU2 7XH, United Kingdom

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

^1,2,3,4Lin, M.,⁴Thiemens, M.H.
Geochemistry, Geophysics, Geosystems 21, Article number e2020GC009051 Link to Article [DOI: 10.1029/2020GC009051]
¹State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China
²University of Chinese Academy of Sciences, Beijing, China
³Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China
⁴Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA, United States

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

^1,2,3Liu, Y.,^1,2,3Xue, D.,^1,2,3Li, W.,^1,2Li, C.,^1,2Wan, B.
Microchemical Journal 158, 105221 Link to Article [DOI: 10.1016/j.microc.2020.105221]
¹State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China
²Innovation Academy for Earth Science, Chinese Academy of Sciences, Beijing, 100029, China
³College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China

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

¹A.A.Fraeman et al. (>10)
Journal of Geophysical Research, Planets (in Press) Link to Article [https://doi.org/10.1029/2019JE006294]
¹Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
Published by arrangement with John Wiley & Sons

Visible/short‐wave infrared spectral data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) show absorptions attributed to hematite at Vera Rubin ridge (VRR), a topographic feature on northwest Mt. Sharp. The goals of this study are to determine why absorptions caused by ferric iron are strongly visible from orbit at VRR, and to improve interpretation of CRISM data throughout lower Mt. Sharp. These goals are achieved by analyzing coordinated CRISM and in situ spectral data along the Curiosity Mars rover’s traverse. VRR bedrock within areas that have the deepest ferric absorptions in CRISM data also have the deepest ferric absorptions measured in situ . This suggests strong ferric absorptions are visible from orbit at VRR because of the unique spectral properties of VRR bedrock. Dust and mixing with basaltic sand additionally inhibit the ability to measure ferric absorptions in bedrock stratigraphically below VRR from orbit. There are two implications of these findings: (1) Ferric absorptions in CRISM data initially dismissed as noise could be real, and ferric phases are more widespread in lower Mt. Sharp than previously reported, (2) Patches with the deepest ferric absorptions in CRISM data are, like VRR, reflective of deeper absorptions in the bedrock. One model to explain this spectral variability is late‐stage diagenetic fluids that changed the grain size of ferric phases, deepening absorptions. Curiosity’s experience highlights the strengths of using CRISM data for spectral absorptions and associated mineral detections, and the caveats in using these data for geologic interpretations and strategic path planning tools.

¹A.A.Fraeman et al. (>10)
Journal of Geophysical Research, Planets (in Press) Link to Article [https://doi.org/10.1029/2020JE006527]
¹Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
Published by arrangement with John Wiley & Sons

This paper provides an overview of the Curiosity rover’s exploration at Vera Rubin ridge and summarizes the science results. Vera Rubin ridge (VRR) is a distinct geomorphic feature on lower Aeolis Mons (informally known as Mt. Sharp) that was identified in orbital data based on its distinct texture, topographic expression, and association with a hematite spectral signature. Curiosity conducted extensive remote sensing observations, acquired data on dozens of contact science targets, and drilled three outcrop samples from the ridge, as well as one outcrop sample immediately below the ridge. Our observations indicate that strata composing VRR were deposited in a predominantly lacustrine setting and are part of the Murray formation. The rocks within the ridge are chemically in family with underlying Murray formation strata. Red hematite is dispersed throughout much of the VRR bedrock, and this is the source of the orbital spectral detection. Gray hematite is also present in isolated, gray‐colored patches concentrated towards the upper elevations of VRR, and these gray patches also contain small, dark Fe‐rich nodules. We propose that VRR formed when diagenetic event(s) preferentially hardened rocks, which were subsequently eroded into a ridge by wind. Diagenesis also led to enhanced crystallization and/or cementation that deepened the ferric‐related spectral absorptions on the ridge, which helped make them readily distinguishable from orbit. Results add to existing evidence of protracted aqueous environments at Gale crater and give new insight into how diagenesis shaped Mars’ rock record.