Trace element composition of silicate minerals in the porphyritic and nonporphyritic chondrules of Elenovka (L5) and Knyahinya (L/Ll5) meteorites

1Kristina Sukhanova,1,2Sergey Skublov,1Olga Galankina,2ElenaKotova
Geochemistry (Chemie der Erde) (in Press) Link to Article []
1Institute of Precambrian Geology and Geochronology, Russian Academy of Sciences, Makarova emb. 2, 199034 St.-Petersburg, Russia
2Saint Petersburg Mining University, 21st Line 2, 199106 St.-Petersburg, Russia
Copyright Elsevier

The results of SIMS and EPMA studies on the silicate minerals and bulk compositions (SEM-EDS) of porphyritic and nonporphyritic chondrules from Elenovka and Knyahinya meteorites are reported. The trace element composition of silicate minerals (olivine, low-Са pyroxene) in equilibrated ordinary chondrites (EOC) has not been affected considerably by thermal metamorphism on the chondritic parent bodies. Therefore, equilibrated chondrites can be used for chondrule-forming processes studies. Low-Са pyroxene in nonporphyritic chondrules contains higher REE, Ba, Sr concentrations than that in porphyritic chondrules at similar trace element concentrations in the olivine of chondrules. The data obtained indicate that the formation of non-porphyritic chondrules was triggered by an increase in the cooling rate of chondrules upon the formation of pyroxene, rather than a difference in the initial conditions of chondrule formation. Higher refractory incompatible element (Nb, LREE) concentrations in the olivine of chondrules than those in the olivine of the matrix and contrasting trace element (Zr, Sr, Cr, REE) concentrations in the low-Са pyroxene of the chondrules and the matrix suggest that the matrix and chondrules of the meteorites formed in one reservoir under different physico-chemical conditions (density, redox state, rotation speed, homogeneity, temperature, shocks, electrical discharge, etc.).

Precious and structural metals on asteroids

1,2Kevin M.Cannon,3Matt Gialich,3Jose Acain
Planetary and Space Science (in Press) Open Access Link to Article []
1Department of Geology and Geological Engineering, Colorado School of Mines, Golden, CO, 80401, USA
2Space Resources Program, Colorado School of Mines, Golden, CO, 80401, USA
3AstroForge Inc., Huntington Beach, CA, 92649, USA

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

Elemental composition of manganese- and phosphorus-rich nodules in the Knockfarril Hill member, Gale crater, Mars

1S.J.Van Bommel et al. (>10)
Icarus (in Press) Link to Article []
1McDonnell Center for the Space Sciences, Department of Earth and Planetary Sciences, Washington University in St. Louis, St. Louis, MO 63130, USA
Copyright Elsevier

The Mars Science Laboratory rover Curiosity encountered nodules rich in manganese and phosphorus while exploring the Knockfarril Hill member of Gale crater on Mars. Deconvolution of X-ray spectroscopy data acquired by the Alpha Particle X-ray Spectrometer (APXS) at the spectral level indicate P2O5 concentrations possibly in excess of 18 wt% and MnO exceeding 8 wt%. The nodules occur intermittently in ~mm-thick layers concordant with the sedimentary laminae, extending up to ~10 cm laterally. Calcium sulfate associated with the nodules is interpreted as having precipitated from fluid that infiltrated between the nodule-bearing bedding planes in a separate and subsequent fluid event. Though the Mn- and P-bearing phase(s) was(were) not definitively identified by X-ray diffraction, evolved gas analyses show that the oxidation state of Mn is most likely 2 + .

Sample studies and SELENE (Kaguya) observations of purest anorthosite (PAN) in the primordial lunar crust for future sample return mission

1Hiroshi Nagaoka,2Makiko Ohtake,3Yuzuru Karouji,4Masahiro Kayama,3Yoshiaki Ishihara5 Satoru Yamamoto,6Risa Sakai
Icarus (in Press) Link to Article []
1Cluster for Pioneering Research, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
2The University of Aizu, Ikki Machi, Tsuruga, Aizu Wakamatsu City 965-8580, Japan
3JAXA Space Exploration Center, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara 252-5210, Japan
4Department of General Systems Studies, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan
5Geological Survey of Japan (GSJ), National Institute of Advanced Industrial Science and Technology (AIST), Central 7, Higashi 1-1-1, Tsukuba 305-8567, Japan
6Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210, Japan
Copyright Elsevier

Purest anorthosite (PAN), which consists mostly of plagioclase (≥98%), provides key information for understanding the deep crust of the Moon, because PAN observed at central peaks of large impact craters was uplifted from a deep-seated layer. For future sample return of PAN, we examined the visible and near-infrared spectra of lunar meteorites and the mineralogical and petrological studies for Apollo FAN 60015. Sample analyses for lunar meteorites and Apollo FAN 60015 showed the existence of PAN in lunar samples. However, PAN clasts in lunar meteorites were so small that not enough sampled material could be secured for multiple analyses, such as determining their crystallization ages. The lunar meteorites were also heavily brecciated by multiple impacts on the surface. The brecciation and recrystallization on the surface may have disturbed the original information (i.e., age, texture, etc). Therefore, sample return of PAN rocks that have recently fallen from the central peaks of the large craters is required for analysis to determine the parent magma composition and timing of PAN formation. We investigated the PAN distributions in Jackson crater on the lunar farside and found that PAN rocks are widely distributed over the central peak and parts of the crater wall, using SELENE (Kaguya) observational data to locate where PAN would best be collected from the lunar surface. Based on the slope that a rover can manage, we recommend two areas appropriate for collecting samples of PAN rocks that have separated from the central peak.

Three-dimensional imaging of high-velocity-impact induced crack growth in carbonaceous meteorites

1Tatsuhiro Michikami et al. (>10)
Icarus (in Press) Link to Article []
1Faculty of Engineering, Kindai University, Hiroshima Campus, 1 Takaya Umenobe, Higashi-Hiroshima, Hiroshima 739-2116, Japan
Copyright Elsevier

The material strength of meteorites provides useful information on the make-up and history of asteroids. However, the unique determination of the material strength of a meteorite is difficult because of the wide range of strengths many meteorites exhibit. Even within a single sample, complicated textures and mineral granular compositions make measurements difficult. Michikami et al. (2019) investigated the impact-induced crack growth in ordinary (L5) chondrites and indicated that crack growth is largely affected by the strength of individual mineral grains (and/or chondrules). In this study, we examine the strengths of mineral grains in carbonaceous meteorites qualitatively. To this end, we use X-ray microtomography to investigate how chondrules are affected by impact-induced crack growth in carbonaceous meteorites. Spherical alumina projectiles with a diameter of 1.0 mm were fired into the surfaces of seven Allende (CV) meteorite target samples with sizes of ~1 to 2 cm at a nominal impact velocity of 2.0 km/s. In addition, spherical glass projectiles with a diameter 0.8 mm were fired into the target surfaces of two Murchison (CM) and two Aguas Zarcas (CM) meteorite target samples with sizes of ~2 cm at a nominal impact velocity of 4.0 km/s. The results show that most cracks in CV chondrites tend to grow along the boundary surfaces of the chondrules, while most chondrule-related cracks in CM samples grow regardless of the boundary surfaces of the chondrules. This suggests that crack growth is largely affected by the chondrules’ strength as indicated by Michikami et al. (2019). The weaker the strength of chondrules, the more likely crack growth tends to occur regardless of chondrule boundaries. We found that the mesostasis of chondrules in CM meteorite Murchison (and likely Aguas Zarcas) has experienced aqueous alteration and the chondrules have become structurally weak as a whole. This indicates that impact-induced crack propagation in CM chondrites differs from thermal-fatigue induced crack propagation inferred from previous studies. As the sample material to be returned from asteroid Bennu is considered to be related to CM chondrites, we propose that observation of the cracks in chondrules in Bennu samples might tell us whether those cracks are impact- or thermal-fatigue-induced.

Shidian meteorite, a new fall analog of near-Earth asteroid (101955) Bennu

1,2Yan Fan et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article []
1State Key Laboratory of Continental Dynamics and Department of Geology, Northwest University, Xi’an, 710069 China
2Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081 China
Published by arrangement with John Wiley & Sons

Shidian is a recent meteorite which fell in Yunnan province, China, on November 27, 2017, and has been classified as a CM2 chondrite. Petrography, mineralogy, oxygen and chromium isotopic composition, reflectance spectrum, and density studies of Shidian are reported in this study. Clasts with different aqueous alteration degree, two type 1 clasts with nontypical CM petrography, and one metamorphic clast are observed in Shidian. Mineralogically, Shidian main body consists of phyllosilicates (∼70 vol%), forsterite (∼13 vol%), fayalitic olivine, carbonates, sulfide, high-Ca pyroxene, magnetite framboids, and Fe-Ni metal. The average electron microprobe analysis (EMPA) analytical totals of phyllosilicates are 84.07 ± 1.75 wt%, with average FeO/SiO2 of tochilinite–cronstedtite intergrowths (TCIs) in different clasts ranging from 1.18 to 3.29. The bulk geochemical composition is characterized by flat rare earth element pattern, and by depletion of highly volatile elements. The whole rock oxygen isotopic composition is −0.51 ± 0.73‰, 5.44 ± 1.01‰, and −3.38 ± 0.20‰ for δ17O, δ18O, and Δ17O, respectively, with bulk chromium isotopic composition as ε54Cr = 1.00 ± 0.11. The grain density, bulk density, and porosity are 2.758 ± 0.008 g cm−3, 2.500 ± 0.004 g cm−3, and 9.37 ± 0.59%, respectively. The reflectance spectrum shows “blue” (negative) continuum slope across the visible and near-infrared range, with characteristic absorption features (such as 0.765, 0.923, and 1.160 μm for phyllosilicates). These characteristics indicate that Shidian is an unheated, brecciated CM chondrite and may be an analog of asteroid Bennu.

Carbon as a key driver of super-reduced explosive volcanism on Mercury: Evidence from graphite-melt smelting experiments

1Kayla Iacovino,2Francis M.McCubbin,3Kathleen E.Vander Kaaden,1Joanna Clark,4Axel Wittmann,1Ryan S.Jakubek,1Gordon M.Moore,2Marc D.Fries,1Doug Archer,2Jeremy W.Boyce
Earth and Planetary Science Letters 602, 117908 Link to Article []
1ARES, Jacobs/NASA Johnson Space Center, 2101 E NASA Pkwy, Houston, TX 77058 USA
2ARES, NASA Johnson Space Center, 2101 E NASA Pkwy, Houston, TX 77058 USA
3NASA Headquarters, Mary W. Jackson Building, Washington, D.C., 20546 USA
4Eyering Materials Center, Arizona State University, 1001 S. McAllister Ave., Tempe, AZ 95287-8301 USA
Copyright Elsevier

Here we present the results of experiments designed to reproduce the interaction between super-solidus mercurian magmas and graphite at high temperatures (ramped up from ambient temperature to 1195–1390 °C) and low pressure (10 mbar). The compositions of resultant gases were measured in situ with a thermal gravimeter/differential scanning calorimeter connected to a mass spectrometer configured to operate under low pressures and reducing conditions. Solid run products were analyzed by electron microprobe and Raman spectroscopy. Three magma starting compositions were based on the composition of the Borealis Planitia region (termed NVP for the Northern Volcanic Plains) on Mercury ± alkali metals, sulfur, and transition metal oxides. Smelting between FeOmelt and graphite was observed above 1100 °C, evidenced by the generation of CO and CO2 gas and the formation of Fe-Si metal alloys, which were found in contact with residual graphite grains. Experiments with transition metal oxide-free starting compositions did not produce metal alloys and showed no significant gas production. In all runs that produced gas, C-O-H±S species dominated the degassing vapor. Our results suggest that the consideration of graphite smelting processes can significantly increase calculated eruption velocities and that gas produced by smelting alone can account for >75% of the pyroclastic deposits identified on Mercury. A combination of S-H-degassing and CO-CO2 production from smelting can explain all but the single largest pyroclastic deposit on Mercury.

Diverse Oxygen Isotopic Compositions Among Cometary Vapor-Phase Condensates

1,2Kainen L.Utt,1,2Ryan C.Ogliore,1,2Nan Liu,3Alexander N.Krot,3John P.Bradley,4Donald E.Brownlee,4David J.Joswiak
Geochimica et Cosmochimica Acta (in Press) Link to Article []
1Department of Physics, Washington University in St. Louis, St. Louis, MO 63130
2McDonnell Center for the Space Sciences, Washington University in St. Louis, St. Louis, MO 63130
3Hawaii Institute of Geophysics and Planetology, University of Hawaii at Mānoa, Honolulu, HI 96822
4Department of Astronomy, University of Washington, Seattle, WA 98195
Copyright Elsevier

Filamentary enstatite crystals, formed by gas-solid condensation in the solar nebula, are found in chondritic porous interplanetary dust particles of probable cometary origin. We measured the oxygen isotopic composition of four filamentary enstatite grains, two whiskers (1.8μm and 2.3μm in length) and two ribbons (3.4μm and 6.1μm in length), from the giant cluster interplanetary dust particle U2-20 GCP using NanoSIMS ion imaging. These grains represent both the 16O-rich solar (δ17,18O ≈-70 ‰) and 16O-poor planetary (δ17,18O ≈0 ‰) isotope reservoirs. Our measurements provide evidence for very early vaporization of dust-poor and dust-rich regions of the solar nebula, followed by condensation and outward transport of crystalline dust to the comet-forming region very far from the Sun. Similar processes are likely responsible for the crystalline silicates observed in the outer regions of protoplanetary disks elsewhere in the Galaxy.

Preservation of Terrestrial Microorganisms and Organics Within Alteration Products of Chondritic Meteorites from the Nullarbor Plain, Australia

1Tait, Alastair W.,1,2Wilson, Siobhan A.,1Tomkins, Andrew G.,1,3Hamilton, Jessica L.,4,5Gagen, Emma J.,6Holman, Alex I.,6Grice, Kliti,7Preston, Louisa J.,3Paterson, David J.,4Southam, Gordon
Astrobiology 22, 399-415 Link to Article [DOI 10.1089/ast.2020.2387]
1School of Earth, Atmosphere and Environment, Monash University, Room 109, 9 Rainforest Walk, Melbourne, 3800, Vic, Australia
2Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB, Canada
3Australian Synchrotron, ANSTO, Clayton, VIC, Australia
4School of Earth and Environmental Sciences, University of Queensland, St. Lucia, QLD, Australia
5Australian Centre for Ecogenomics, School of Chemistry and Molecular Biosciences, University of Queensland, St Lucia, QLD, Australia
6Western Australian Organic and Isotope Geochemistry Centre, Institute for Geoscience Research, Curtin University, Perth, WA, Australia
7Department of Earth Sciences, Natural History Museum, London, United Kingdom

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

Unique evidence of fluid alteration in the Kakowa (L6) ordinary chondrite

1Baziotis I.P.,2Ma C.,2Guan Y.,3Ferrière L.,1Xydous S.,2Hu J.,4Kipp M.A.,4Tissot F.L.H.,2Asimow P.D.
Scientific Reports 12, 5520 Open Access Link to Article [DOI 10.1038/s41598-022-09465-6]
1Agricultural University of Athens, Iera Odos 75, Athens, 11755, Greece
2Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, 91125, CA, United States
3Natural History Museum Vienna, Burgring 7, Vienna, 1010, Austria
4The Isotoparium, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, 91125, CA, United States

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