Meteoritic Fe-Ni alloys: A review of 57Fe Mössbauer spectroscopy studies

1Rosa B.Scorzelli,2Edivaldodos Santos
Geochemistry (Chemie der Erde) (in Press) Link to Article [https://doi.org/10.1016/j.chemer.2019.125547]
1Centro Brasileiro de Pesquisas Físicas – CBPF, Rua Dr. Xavier Sigaud 150, 22290-180, Rio de Janeiro, Brazil
2Instituto de Ciência e Tecnologia – ICT/UFVJM, Rodovia MGT 367 – km 583, n° 5000, 39100-000, Minas Gerais, Brazil
Copyright Elsevier

Discovered by Rudolph L. Mössbauer in 1957, the Mössbauer effect (i.e. gamma-resonance spectroscopy) is the phenomenon of the emission or absorption of a gamma ray without loss of energy due to recoil of the nucleus and without thermal broadening. This technique has been applied to many science fields (e.g., physics, chemistry, geology, biology), since it provides information about the nuclear and electronic properties of materials. In this paper, a review of works focusing on the application of 57Fe Mössbauer spectroscopy study of the meteoritic Fe-Ni system will be reported.

The mineral diversity of Jezero crater: Evidence for possible lacustrine carbonates on Mars

1,5Briony H.N.Horgan,2Ryan B.Anderson,3Gilles Dromart,4Elena S.Amador,4Melissa S.Rice
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2019.11352]
1Dept. of Earth, Atmospheric, & Planetary Sciences, Purdue University, West Lafayette, IN, USA
2U.S. Geological Survey, Astrogeology Center, Flagstaff, AZ, USA
3Laboratoire de Géologie de Lyon, Université de Lyon, 69364 Lyon, France
4Division of Geological & Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
5Dept. of Physics & Dept. of Geology, Western Washington University, Bellingham, WA, USA
Copyright Elsevier

Noachian-aged Jezero crater is the only known location on Mars where clear orbital detections of carbonates are found in close proximity to clear fluvio-lacustrine features indicating the past presence of a paleolake; however, it is unclear whether or not the carbonates in Jezero are related to the lacustrine activity. This distinction is critical for evaluating the astrobiological potential of the site, as lacustrine carbonates on Earth are capable of preserving biosignatures at scales that may be detectable by a landed mission like the Mars 2020 rover, which is planned to land in Jezero in February 2021. In this study, we conduct a detailed investigation of the mineralogical and morphological properties of geological units within Jezero crater in order to better constrain the origin of carbonates in the basin and their timing relative to fluvio-lacustrine activity. Using orbital visible/near-infrared hyperspectral images from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) along with high resolution imagery and digital elevation models, we identify a distinct carbonate-bearing unit, the “Marginal Carbonates,” located along the inner margin of the crater, near the largest inlet valley and the western delta. Based on their strong carbonate signatures, topographic properties, and location in the crater, we propose that this unit may preserve authigenic lacustrine carbonates, precipitated in the near-shore environment of the Jezero paleolake. Comparison to carbonate deposits from terrestrial closed basin lakes suggests that if the Marginal Carbonates are lacustrine in origin, they could preserve macro- and microscopic biosignatures in microbialite rocks like stromatolites, some of which would likely be detectable by Mars 2020. The Marginal Carbonates may represent just one phase of a complex fluvio-lacustrine history in Jezero crater, as we find that the spectral diversity of the fluvio-lacustrine deposits in the crater is consistent with a long-lived lake system cataloging the deposition and erosion of regional geologic units. Thus, Jezero crater may contain a unique record of the evolution of surface environments, climates, and habitability on early Mars.

Segregation of Na, K, Rb and Cs into the cores of Earth, Mars and Vesta constrained with partitioning experiments

1A.Boujibar,2K.Righter,1E.S.Bullock,1Z.Du,1Y.Fei
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2019.11.014]
1Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Road NW, Washington, DC, United States
2NASA Johnson Space Center, 2101 NASA Pkwy, Houston, TX 77058, United States
Copyright Elsevier

Alkali metals Na, K, Rb and Cs are depleted in planetary mantles and their depletion is commonly attributed to the effect of volatility during the condensation of the first solids in the solar nebula or the high temperatures involved during planetary growth. Most models of planetary differentiation assume that alkalis behave entirely as lithophile elements and do not participate in core segregation. Here, we tested this hypothesis by determining experimentally the partitioning of Na, Cs and Rb between iron sulfide and silicate (Dsulf/sil) and combining it with available data from the literature on K, Na and Cs partitioning. Our experiments were conducted at 1-3.5 GPa, with an additional one at 8 GPa, 1600 to 1900 °C, and varying FeO contents, which lead to a relatively large range of O content in the sulfide phases (up to 13 wt%). We found maximum Dsulf/sil of 0.8, 0.4, and 0.36 for Na, Cs and Rb respectively. In addition, Dsulf/sil for Na, K, Cs and Rb increases with temperature and O content in the sulfide and decreases with FeO content in the silicate. The degree of polymerization of the silicate melt and the S content of the sulfide additionally increase Dsulf/sil for Na, K and Cs. Since the solubility of O in sulfides is correlated with the FeO content of the silicate and both have opposite effects on Dsulf/sil, varying the oxidation state of equilibrating material does not significantly affect Dsulf/sil, which is more controlled by the temperature of equilibration. We modeled core formation for Earth, Mars and asteroid Vesta, assuming that some of the accreted embryos contained immiscible sulfides, that segregated into planetary cores. Our results show that with such a scenario, significant amounts of Na, K, Cs and Rb were sequestered in planetary cores, leading to core/mantle distribution of alkalis between 4.10-5 and 0.15. The depletion of alkalis in the mantles of Earth, Mars and Vesta could have resulted from combined effects of volatility and core segregation, but are largely due to volatile depletion in the accreting materials.

Accretionary mixing of a eucrite impactor and the regolith of the L chondrite parent body

1,2Brendt C. Hyde,1Kimberly T. Tait,2Desmond E. Moser,3Douglas Rumble III,1,4Michelle S. Thompson
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13416]
1Department of Natural History, Royal Ontario Museum, Toronto, ON, Canada, M5S 2C6
2Department of Earth Sciences, University of Western Ontario, London, ON, Canada, N6A 5B7
3Carnegie Institution of Washington, Washington, DC, 20015 USA
4Department of Earth, Atmospheric and Planetary Sciences, Purdue University, West Lafayette, IN, 47907 USA
Published by arrangement with John Wiley & Sons

Northwest Africa (NWA) 869 is the largest sample of chondritic regolith breccia, making it an ideal source for research on accretionary processes and primordial chemical mixing. One such process can be seen in detail through the first identification of a eucrite impactor clast in an L chondrite breccia. The ~7 mm diameter clast has oxygen isotope compositions (Δ17O = −0.240, −0.258‰) and pigeonite and augite compositions typical for eucrites, but with high areal abundance of silica (9.5%) and ilmenite (1.5%). The rim around the clast is a mixture of breccia and igneous phases, the latter due to either impactor‐triggered melting or later metamorphism. The rim has an oxygen isotope composition falling on a mixing line between known eucrite and L chondrite compositions (Δ17O = 0.326‰) and, coincidentally, on the Mars fractionation line. Pyroxene grains from the melt component in the rim have compositions that fall on a mixing line between the average eucrite pyroxene composition and equilibrated L chondrite composition. The margins of chondritic olivine crystal clasts in the rim are enriched in Fe as a result of diffusion from the Fe‐rich melt and suggest cooling on the scale of hours. The textures and chemical mixing observed provide evidence for an unconsolidated L chondrite target material, differing from the current state of NWA 869 material. The heterogeneity of oxygen isotope and chemical signatures at this small length scale serve as a cautionary note when extrapolating from small volumes of materials to deduce planetesimal source characteristics.

A detailed mineralogical, petrographic, and geochemical study of the highly reduced chondrite, Acfer 370

1,2Giovanni Pratesi,3Stefano Caporali,4Richard C. Greenwood,5Vanni Moggi Cecchi,1Ian A. Franchi
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13409]
1Dipartimento di Scienze della Terra, Università degli Studi di Firenze, Via Giorgio La Pira, 4, 50121 Firenze, Italy
2INAF‐IAPS, Via Fosso del Cavaliere 100, 00133 Rome, Italy
3Dipartimento di Ingegneria Industriale, Università degli Studi di Firenze, Via Santa Marta 3, 50139 Firenze, Italy
4Planetary and Space Sciences, The Open University, Milton Keynes, MK7 6AA UK
5Museo di Storia Naturale, Università degli Studi di Firenze, Via Giorgio La Pira, 4, 50121 Firenze, Italy
Published by arrangement with John Wiley & Sons

Among the many ungrouped meteorites, Acfer 370, NWA 7135, and El Médano 301—probably along with the chondritic inclusion in Cumberland Falls and ALHA 78113—represent a homogeneous grouplet of strongly reduced forsterite‐rich chondrites characterized by common textural, chemical, mineralogical, and isotopic features. All of these meteorites are much more reduced than OCs, with a low iron content in olivine and low‐Ca pyroxene. In particular, Acfer 370 is a type 4 chondrite that has olivine and low‐Ca pyroxene compositional ranges of Fa 5.2–5.8 and Fs 9.4–33.4, respectively. The dominant phase is low‐Ca pyroxene (36.3 vol%), followed by Fe‐Ni metal (16.3 vol%) and olivine (15.5 vol%); nevertheless, considering the Fe‐oxyhydroxide (due to terrestrial weathering), the original metal content was around 29.6 vol%. Finally, the mean oxygen isotopic composition Δ17O = +0.68‰ along with the occurrence of a silica phase, troilite, Ni‐rich phosphides, chromite, and oldhamite confirms that these ungrouped meteorites have been affected by strong reduction and are different from any other group recognized so far.

Physical Characterization of Active Asteroid (6478) Gault

1Juan A. Sanchez,2Vishnu Reddy,3Audrey Thirouin,4Edward L. Wright,5,6Tyler R. Linder,2Theodore Kareta,2Benjamin Sharkey
The Astrophysical Journal Letters 881, L6 Link to Article [DOI
https://doi.org/10.3847/2041-8213/ab31ac]
1Planetary Science Institute, 1700 East Fort Lowell Road, Tucson, AZ 85719, USA
2Lunar and Planetary Laboratory, University of Arizona, 1629 East University Blvd, Tucson, AZ 85721-0092, USA
3Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001, USA
4Division of Astronomy and Astrophysics, University of California Los Angeles, 430 Portola Plaza, Box 951547, Los Angeles, CA 90095-1547, USA
5Astronomical Research Institute, 1015 Cr 1300N, Sullivan, IL 61951, USA
6University of North Dakota, Clifford Hall Room 512, 4149 University Avenue Stop 9008, Grand Forks, ND 58202, USA

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Formation of Transition Alumina Dust around Asymptotic Giant Branch Stars: Condensation Experiments using Induction Thermal Plasma Systems

1,2Aki Takigawa,3Tae-Hee Kim,4Yohei Igami,2Tatsuki Umemoto,2,7Akira Tsuchiyama,5Chiyoe Koike,2Junya Matsuno,6Takayuki Watanabe
The Astrophysical Journal Letters, 878, L7 Link to Article [DOI
https://doi.org/10.3847/2041-8213/ab1f80]
1The Hakubi Center for Advanced Research, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo, Kyoto 606-8502, Japan
2Division of Earth and Planetary Sciences, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo, Kyoto 606-8502, Japan
3Institute for Nuclear Science and Technology, Department of Nuclear and Energy Engineering, Jeju National University, 102 Jejudaehak-ro, Jeju-si, Jeju, 63243, Republic of Korea
4Institute of Materials and Systems for Sustainability, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
5Department of Physics, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu-shi, Shiga 525-8577, Japan
6Department of Chemical Engineering, Kyushu University, Fukuoka 819-0395, Japan
7Present addresses: Research Organization of Science and Technology, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga 525-8577, Japan, and Guangzhou Institute of Geochemistry, Chinese Academy of Sciences 511 Kehua Street, Wushan, Tianhe District, Guangzhou, 510640, China.

 

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