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3. Pyrrhotites in asteroid 162173 Ryugu: Records of the initial changes on their surfaces with aqueous alteration

Author

Yui, Hiroharu, Urashima, Shu-hei, Onose, Morihiko, Morita, Mayu, Komatani, Shintaro, Nakai, Izumi, Abe, Yoshinari, Terada, Yasuko, Homma, Hisashi, Motomura, Kazuko, Ichida, Kiyohiro, Yokoyama, Tetsuya, Nagashima, Kazuhide, Aléon, Jérôme, M. O’D. Alexander, Conel, Amari, Sachiko, Amelin, Yuri, Bajo, Ken-ichi, Bizzarro, Martin, Bouvier, Audrey, Carlson, Richard W., Chaussidon, Marc, Choi, Byeon-Gak, Dauphas, Nicolas, Davis, Andrew M., Fujiya, Wataru, Fukai, Ryota, Gautam, Ikshu, Haba, Makiko K., Hibiya, Yuki, Hidaka, Hiroshi, Hoppe, Peter, Huss, Gary R., Iizuka, Tsuyoshi, Ireland, Trevor R., Ishikawa, Akira, Itoh, Shoichi, Kawasaki, Noriyuki, Kita, Noriko T., Kitajima, Kouki, Kleine, Thorsten, Krot, Sasha, Liu, Ming-Chang, Masuda, Yuki, Moynier, Frédéric, Nguyen, Ann, Nittler, Larry, Pack, Andreas, Park, Changkun, Piani, Laurette, Qin, Liping, Di Rocco, Tommaso, Russell, Sara S., Sakamoto, Naoya, Schönbächler, Maria, Tafla, Lauren, Tang, Haolan, Terada, Kentaro, Usui, Tomohiro, Wada, Sohei, Wadhwa, Meenakshi, Walker, Richard J., Yamashita, Katsuyuki, Yin, Qing-Zhu, Yoneda, Shigekazu, Young, Edward D., Zhang, Ai-Cheng, Nakamura, Tomoki, Naraoka, Hiroshi, Noguchi, Takaaki, Okazaki, Ryuji, Sakamoto, Kanako, Yabuta, Hikaru, Abe, Masanao, Miyazaki, Akiko, Nakato, Aiko, Nishimura, Masahiro, Okada, Tatsuaki, Yada, Toru, Yogata, Kasumi, Nakazawa, Satoru, Saiki, Takanao, Tanaka, Satoshi, Terui, Fuyuto, Tsuda, Yuichi, Watanabe, Sei-ichiro, Yoshikawa, Makoto, Tachibana, Shogo, and Yurimoto, Hisayoshi

Published
2024
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6. Pervasive aqueous alteration in the early Solar System revealed by potassium isotopic variations in Ryugu samples and carbonaceous chondrites

Author

Hu, Yan, Moynier, Frédéric, Dai, Wei, Paquet, Marine, Yokoyama, Tetsuya, Abe, Yoshinari, Aléon, Jérôme, Alexander, Conel M. O'D., Amari, Sachiko, Amelin, Yuri, Bajo, Ken-ichi, Bizzarro, Martin, Bouvier, Audrey, Carlson, Richard W., Chaussidon, Marc, Choi, Byeon-Gak, Dauphas, Nicolas, Davis, Andrew M., Di Rocco, Tommaso, Fujiya, Wataru, Fukai, Ryota, Gautam, Ikshu, Haba, Makiko K., Hibiya, Yuki, Hidaka, Hiroshi, Homma, Hisashi, Hoppe, Peter, Huss, Gary R., Ichida, Kiyohiro, Iizuka, Tsuyoshi, Ireland, Trevor R., Ishikawa, Akira, Itoh, Shoichi, Kawasaki, Noriyuki, Kita, Noriko T., Kitajima, Koki, Kleine, Thorsten, Komatani, Shintaro, Krot, Alexander N., Liu, Ming-Chang, Masuda, Yuki, Morita, Mayu, Motomura, Kazuko, Nakai, Izumi, Nagashima, Kazuhide, Nesvorný, David, Nguyen, Ann, Nittler, Larry, Onose, Morihiko, Pack, Andreas, Park, Changkun, Piani, Laurette, Qin, Liping, Russell, Sara S., Sakamoto, Naoya, Schönbächler, Maria, Tafla, Lauren, Tang, Haolan, Terada, Kentaro, Terada, Yasuko, Usui, Tomohiro, Wada, Sohei, Wadhwa, Meenakshi, Walker, Richard J., Yamashita, Katsuyuki, Yin, Qing-Zhu, Yoneda, Shigekazu, Young, Edward D., Yui, Hiroharu, Zhang, Ai-Cheng, Nakamura, Tomoki, Naraoka, Hiroshi, Noguchi, Takaaki, Okazaki, Ryuji, Sakamoto, Kanako, Yabuta, Hikaru, Abe, Masanao, Miyazaki, Akiko, Nakato, Aiko, Nishimura, Masahiro, Okada, Tatsuaki, Yada, Toru, Yogata, Kasumi, Nakazawa, Satoru, Saiki, Takanao, Tanaka, Satoshi, Terui, Fuyuto, Tsuda, Yuichi, Watanabe, Sei-ichiro, Yoshikawa, Makoto, Tachibana, Shogo, and Yurimoto, Hisayoshi

Published
2024
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7. Chondrule-like objects and Ca-Al-rich inclusions in Ryugu may potentially be the oldest Solar System materials

Author

Nakashima, Daisuke, Nakamura, Tomoki, Zhang, Mingming, Kita, Noriko T., Mikouchi, Takashi, Yoshida, Hideto, Enokido, Yuma, Morita, Tomoyo, Kikuiri, Mizuha, Amano, Kana, Kagawa, Eiichi, Yada, Toru, Nishimura, Masahiro, Nakato, Aiko, Miyazaki, Akiko, Yogata, Kasumi, Abe, Masanao, Okada, Tatsuaki, Usui, Tomohiro, Yoshikawa, Makoto, Saiki, Takanao, Tanaka, Satoshi, Nakazawa, Satoru, Terui, Fuyuto, Yurimoto, Hisayoshi, Noguchi, Takaaki, Yabuta, Hikaru, Naraoka, Hiroshi, Okazaki, Ryuji, Sakamoto, Kanako, Watanabe, Sei-ichiro, Tachibana, Shogo, and Tsuda, Yuichi

Published
2023
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8. Contribution of Ryugu-like material to Earth’s volatile inventory by Cu and Zn isotopic analysis

Author

Paquet, Marine, Moynier, Frederic, Yokoyama, Tetsuya, Dai, Wei, Hu, Yan, Abe, Yoshinari, Aléon, Jérôme, O’D. Alexander, Conel M., Amari, Sachiko, Amelin, Yuri, Bajo, Ken-ichi, Bizzarro, Martin, Bouvier, Audrey, Carlson, Richard W., Chaussidon, Marc, Choi, Byeon-Gak, Dauphas, Nicolas, Davis, Andrew M., Di Rocco, Tommaso, Fujiya, Wataru, Fukai, Ryota, Gautam, Ikshu, Haba, Makiko K., Hibiya, Yuki, Hidaka, Hiroshi, Homma, Hisashi, Hoppe, Peter, Huss, Gary R., Ichida, Kiyohiro, Iizuka, Tsuyoshi, Ireland, Trevor R., Ishikawa, Akira, Ito, Motoo, Itoh, Shoichi, Kawasaki, Noriyuki, Kita, Noriko T., Kitajima, Kouki, Kleine, Thorsten, Komatani, Shintaro, Krot, Alexander N., Liu, Ming-Chang, Masuda, Yuki, McKeegan, Kevin D., Morita, Mayu, Motomura, Kazuko, Nakai, Izumi, Nagashima, Kazuhide, Nesvorný, David, Nguyen, Ann N., Nittler, Larry, Onose, Morihiko, Pack, Andreas, Park, Changkun, Piani, Laurette, Qin, Liping, Russell, Sara S., Sakamoto, Naoya, Schönbächler, Maria, Tafla, Lauren, Tang, Haolan, Terada, Kentaro, Terada, Yasuko, Usui, Tomohiro, Wada, Sohei, Wadhwa, Meenakshi, Walker, Richard J., Yamashita, Katsuyuki, Yin, Qing-Zhu, Yoneda, Shigekazu, Young, Edward D., Yui, Hiroharu, Zhang, Ai-Cheng, Nakamura, Tomoki, Naraoka, Hiroshi, Noguchi, Takaaki, Okazaki, Ryuji, Sakamoto, Kanako, Yabuta, Hikaru, Abe, Masanao, Miyazaki, Akiko, Nakato, Aiko, Nishimura, Masahiro, Okada, Tatsuaki, Yada, Toru, Yogata, Kasumi, Nakazawa, Satoru, Saiki, Takanao, Tanaka, Satoshi, Terui, Fuyuto, Tsuda, Yuichi, Watanabe, Sei-ichiro, Yoshikawa, Makoto, Tachibana, Shogo, and Yurimoto, Hisayoshi

Published
2023
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12. Radial transport and nebular thermal processing of millimeter‐sized solids in the Solar protoplanetary disk inferred from Cr‐Ti‐O isotope systematics of chondrules.

Author

Fukuda, Kohei, Hibiya, Yuki, Kastelle, Craig R., Suzuki, Katsuhiko, Iizuka, Tsuyoshi, Yamashita, Katsuyuki, Helser, Thomas E., and Kita, Noriko T.

Abstract

Understanding the material transport and mixing processes in the Solar protoplanetary disk provides important constraints on the origin of chemical and isotopic diversities of our planets. The limited extent of radial transport and mixing between the inner and outer Solar System has been suggested based on a fundamental isotopic dichotomy between non‐carbonaceous (NC) and carbonaceous (CC) meteorite groups. The limited transport and mixing could be further tested by tracing the formation regions of individual meteoritic components, such as Ca‐Al‐rich inclusions (CAIs) and chondrules. Here, we show further evidence for the outward transport of CAIs and chondrules from the inner and subsequent thermal processing in the outer region of the protoplanetary disk based on the petrography and combined Cr‐Ti‐O isotope systematics of chondrules from the Vigarano‐like (CV) carbonaceous chondrite Allende. One chondrule studied consists of an olivine core that exhibits NC‐like Ti and O, but CC‐like Cr isotopic signatures, which is enclosed by a pyroxene igneous rim with CC‐like O isotope ratios. These observations indicate that the olivine core formed in the inner Solar System. The olivine core then migrated into the outer Solar System and experienced nebular thermal processing that generated the pyroxene igneous rim. The nebular thermal processing would result in Cr isotope exchange between the olivine core and CC‐like materials, but secondary alteration effects on the parent body are also responsible for the CC‐like Cr isotope signature. By combining previously reported Cr‐Ti‐O isotope systematics of CV chondrules, we show that some CV chondrules larger than ~1 mm would have formed in the inner Solar System. The accretion of the millimeter‐sized, inner Solar System solids onto the CV carbonaceous chondrite parent body would require their very early migration into the outer Solar System within the first 1 million years after the Solar System formation. [ABSTRACT FROM AUTHOR]

Published
2024
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16. Author Correction: Contribution of Ryugu-like material to Earth’s volatile inventory by Cu and Zn isotopic analysis

Author

Paquet, Marine, Moynier, Frederic, Yokoyama, Tetsuya, Dai, Wei, Hu, Yan, Abe, Yoshinari, Aléon, Jérôme, O’D. Alexander, Conel M., Amari, Sachiko, Amelin, Yuri, Bajo, Ken-ichi, Bizzarro, Martin, Bouvier, Audrey, Carlson, Richard W., Chaussidon, Marc, Choi, Byeon-Gak, Dauphas, Nicolas, Davis, Andrew M., Di Rocco, Tommaso, Fujiya, Wataru, Fukai, Ryota, Gautam, Ikshu, Haba, Makiko K., Hibiya, Yuki, Hidaka, Hiroshi, Homma, Hisashi, Hoppe, Peter, Huss, Gary R., Ichida, Kiyohiro, Iizuka, Tsuyoshi, Ireland, Trevor R., Ishikawa, Akira, Ito, Motoo, Itoh, Shoichi, Kawasaki, Noriyuki, Kita, Noriko T., Kitajima, Kouki, Kleine, Thorsten, Komatani, Shintaro, Krot, Alexander N., Liu, Ming-Chang, Masuda, Yuki, McKeegan, Kevin D., Morita, Mayu, Motomura, Kazuko, Nakai, Izumi, Nagashima, Kazuhide, Nesvorný, David, Nguyen, Ann N., Nittler, Larry, Onose, Morihiko, Pack, Andreas, Park, Changkun, Piani, Laurette, Qin, Liping, Russell, Sara S., Sakamoto, Naoya, Schönbächler, Maria, Tafla, Lauren, Tang, Haolan, Terada, Kentaro, Terada, Yasuko, Usui, Tomohiro, Wada, Sohei, Wadhwa, Meenakshi, Walker, Richard J., Yamashita, Katsuyuki, Yin, Qing-Zhu, Yoneda, Shigekazu, Young, Edward D., Yui, Hiroharu, Zhang, Ai-Cheng, Nakamura, Tomoki, Naraoka, Hiroshi, Noguchi, Takaaki, Okazaki, Ryuji, Sakamoto, Kanako, Yabuta, Hikaru, Abe, Masanao, Miyazaki, Akiko, Nakato, Aiko, Nishimura, Masahiro, Okada, Tatsuaki, Yada, Toru, Yogata, Kasumi, Nakazawa, Satoru, Saiki, Takanao, Tanaka, Satoshi, Terui, Fuyuto, Tsuda, Yuichi, Watanabe, Sei-ichiro, Yoshikawa, Makoto, Tachibana, Shogo, and Yurimoto, Hisayoshi

Published
2023
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22. Late Pebble Accretion of Comet 81P/Wild 2 Nucleus: Evidence from a Plagioclase-bearing Chondrule Fragment, Pyxie.

Author

Zhang, Mingming, Zolensky, Michael E., Fukuda, Kohei, Nakashima, Daisuke, Weisberg, Michael K., and Kita, Noriko T.

Abstract

Comet 81P/Wild 2 is a ∼4.5 km-sized primordial object that almost has not been modified by internal heating by 26Al decay. Its nucleus could have been formed by hierarchical agglomeration or gravitational collapse of pebble swarms concentrated by streaming instability. To shed light on the cometesimal formation mechanism from laboratory sample analysis, we reexamined the 26Al–26Mg isotope systematics of the plagioclase-bearing fragment, Pyxie (from Wild 2 track 81), with significantly improved analytical precision. The revised upper limit of the initial (26Al/27Al)0 of Pyxie is ≤1.5 × 10−6, 2 times smaller than those estimated from other Wild 2 fragments. Assuming homogenous distribution of 26Al in the early solar system, the minimum crystallization age of Pyxie is estimated to be >3.6 Ma after calcium–aluminum-rich inclusions. Additional petrologic examination demonstrated that it is a chondrule fragment formed in disk environments enriched in moderately volatile elements comparable to the Si-rich rim of CR chondrules before accreting by comet Wild 2. The late accretion of the Wild 2 nucleus with most silicates likely from a common source are not favored by the hierarchical agglomeration model that considers early and continuous accretion. Instead, the results are more in line with comet formation by gentle gravitational collapse of pebbles when the 26Al abundance is extremely low (26Al/27Al ≤ 1.5 × 10−6) before gas dispersal. [ABSTRACT FROM AUTHOR]

Published
2024
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23. Disequilibrium oxygen isotope distribution among aqueously altered minerals in Ryugu asteroid returned samples.

Author

Kita, Noriko T., Kitajima, Kouki, Nagashima, Kazuhide, Kawasaki, Noriyuki, Sakamoto, Naoya, Fujiya, Wataru, Abe, Yoshinari, Aléon, Jérôme, Alexander, Conel M. O'D., Amari, Sachiko, Amelin, Yuri, Bajo, Ken‐ichi, Bizzarro, Martin, Bouvier, Audrey, Carlson, Richard W., Chaussidon, Marc, Choi, Byeon‐Gak, Dauphas, Nicolas, Davis, Andrew M., and Di Rocco, Tommaso

Subjects
*OXYGEN isotopes, *COMMODITY exchanges, *ISOTOPE exchange reactions, *CRYSTAL orientation, *ION energy, *DOLOMITE, *CALCITE
Abstract

Oxygen 3‐isotope ratios of magnetite and carbonates in aqueously altered carbonaceous chondrites provide important clues to understanding the evolution of the fluid in the asteroidal parent bodies. We conducted oxygen 3‐isotope analyses of magnetite, dolomite, and breunnerite in two sections of asteroid Ryugu returned samples, A0058 and C0002, using a secondary ion mass spectrometer (SIMS). Magnetite was analyzed by using a lower primary ion energy that reduced instrumental biases due to the crystal orientation effect. We found two groups of magnetite data identified from the SIMS pit morphologies: (1) higher δ18O (from 3‰ to 7‰) and ∆17O (~2‰) with porous SIMS pits mostly from spherulitic magnetite, and (2) lower δ18O (~ −3‰) and variable ∆17O (0‰–2‰) mostly from euhedral magnetite. Dolomite and breunnerite analyses were conducted using multi‐collection Faraday cup detectors with precisions ≤0.3‰. The instrumental bias correction was applied based on carbonate compositions in two ways, using Fe and (Fe + Mn) contents, respectively, because Ryugu dolomite contains higher amounts of Mn than the terrestrial standard. Results of dolomite and breunnerite analyses show a narrow range of ∆17O; 0.0‰–0.3‰ for dolomite in A0058 and 0.2‰–0.8‰ for dolomite and breunnerite in C0002. The majority of breunnerite, including large ≥100 μm grains, show systematically lower δ18O (~21‰) than dolomite (25‰–30‰ and 23‰–27‰ depending on the instrumental bias corrections). The equilibrium temperatures between magnetite and dolomite from the coarse‐grained lithology in A0058 are calculated to be 51 ± 11°C and 78 ± 14°C, depending on the instrumental bias correction scheme for dolomite; a reliable temperature estimate would require a Mn‐bearing dolomite standard to evaluate the instrumental bias corrections, which is not currently available. These results indicate that the oxygen isotope ratios of aqueous fluids in the Ryugu parent asteroid were isotopically heterogeneous, either spatially, or temporary. Initial water ice accreted to the Ryugu parent body might have ∆17O > 2‰ that was melted and interacted with anhydrous solids with the initial ∆17O < 0‰. In the early stage of aqueous alteration, spherulitic magnetite and calcite formed from aqueous fluid with ∆17O ~ 2‰ that was produced by isotope exchange between water (∆17O > 2‰) and anhydrous solids (∆17O < 0‰). Dolomite and breunnerite, along with some magnetite, formed at the later stage of aqueous alteration under higher water‐to‐rock ratios where the oxygen isotope ratios were nearly at equilibrium between fluid and solid phases. Including literature data, δ18O of carbonates decreased in the order calcite, dolomite, and breunnerite, suggesting that the temperature of alteration might have increased with the degree of aqueous alteration. [ABSTRACT FROM AUTHOR]

Published
2024
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27. Enstatite meteorite clasts in Almahata Sitta and other polymict ureilites: Implications for the formation of asteroid 2008 TC3 and the history of enstatite meteorite parent asteroids.

Author

Goodrich, Cyrena Anne, Downes, Hilary, Greenwood, Richard, Ross, Aidan J., Fioretti, Anna Maria, Alexander, Louise, Kita, Noriko T., Butler, Jon, Jercinovic, Michael J., Jenniskens, Peter, and Shaddad, Muawia H.

Subjects
ACHONDRITES, METEORITES, ENSTATITE, ASTEROIDS, OXYGEN isotopes, PETROLOGY
Abstract

The anomalous polymict ureilite Almahata Sitta (AhS) fell in 2008 when asteroid 2008 TC3 disintegrated over Sudan and formed a strewn field of disaggregated clasts of various ureilitic and chondritic types. We studied the petrology and oxygen isotope compositions of enstatite meteorite samples from the University of Khartoum (UoK) collection of AhS. In addition, we describe the first bona fide (3.5 mm‐sized) clast of an enstatite chondrite (EC) in a typical polymict ureilite, Northwest Africa (NWA) 10657. We evaluate whether 2008 TC3 and typical polymict ureilites have a common origin, and examine implications for the history of enstatite meteorite asteroids in the solar system. Based on mineralogy, mineral compositions, and textures, the seven AhS EC clasts studied comprise one EHa3 (S151), one ELb3 (AhS 1002), two EHb4‐5 (AhS 2012, AhS 26), two EHb5‐6 or possibly impact melt rocks (AhS 609, AhS 41), and one ELb6‐7 (AhS 17), while the EC clast in NWA 10657 is EHa3. Oxygen isotope compositions analyzed for five of these are similar to those of EC from non‐UoK collections of AhS, and within the range of individual EC meteorites. There are no correlations of oxygen isotope composition with chemical group or subgroup. The EC clasts from the UoK collection show the same large range of types as those from non‐UoK collections of AhS. The enstatite achondrite, AhS 60, is a unique type (not known as an individual meteorite) that has also been found among non‐UoK AhS samples. EC are the most abundant non‐ureilitic clasts in AhS but previously were thought to be absent in typical polymict ureilites, necessitating a distinct origin for AhS. The discovery of an EC in NWA 10657 changes this. We argue that the types of materials in AhS and typical polymict ureilites are essentially similar, indicating a common origin. We elaborate on a model in which AhS and typical polymict ureilites formed in the same regolith on a ureilitic daughter body. Most non‐ureilitic clasts are remnants of impactors implanted at ~50–60 Myr after CAI. Differences in abundances can be explained by the stochastic nature of impactor addition. There is no significant difference between the chemical/petrologic types of EC in polymict ureilites and individual EC meteorites. This implies that fragments of the same populations of EC parent bodies were available as impactors at ~50–60 Myr after CAI and recently. This can be explained if materials excavated from various depths on EC bodies at ~50–60 Myr after CAI were reassembled into mixed layers, leaving relatively large bodies intact to survive 4 billion years. Polymict ureilites record a critical timestep in the collisional and dynamical evolution of the solar system, showing that asteroids that may have accreted at distant locations had migrated to within proximity of one another by 50–60 Myr after CAI, and providing constraints on the dynamical processes that could have caused such migrations. [ABSTRACT FROM AUTHOR]

Published
2024
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36. Unusual sources of fossil micrometeorites deduced from relict chromite in the small size fraction in ~467 Ma old limestone.

Author

Heck, Philipp R., Schmitz, Birger, Ritter, Xenia, Rout, Surya S., Kita, Noriko T., Defouilloy, Céline, Keating, Katarina, Eisenstein, Kevin, and Terfelt, Fredrik

Subjects
METEORITES, CHROMITE, ACHONDRITES, CHONDRITES, LIMESTONE, ASTEROIDS, SEDIMENTARY rocks, COMPOSITION of grain, MILANKOVITCH cycles
Abstract

Extraterrestrial chrome spinel and chromite extracted from the sedimentary rock record are relicts from coarse micrometeorites and rarely meteorites. They are studied to reconstruct the paleoflux of meteorites to the Earth and the collisional history of the asteroid belt. Minor element concentrations of Ti and V, and oxygen isotopic compositions of these relict minerals were used to classify the meteorite type they stem from, and thus to determine the relative meteorite group abundances through time. While coarse sediment‐dispersed extraterrestrial chrome‐spinel (SEC) grains from ordinary chondrites dominate through the studied time windows in the Phanerozoic, there are exceptions: We have shown that ~467 Ma ago, 1 Ma before the breakup of the L chondrite parent body (LCPB), more than half of the largest (>63 μm diameter) grains were achondritic and originated from differentiated asteroids in contrast to ordinary chondrites which dominated the meteorite flux throughout most of the past 500 Ma. Here, we present a new data set of oxygen isotopic compositions and elemental compositions of 136 grains of a smaller size fraction (32–63 μm) in ~467 Ma old pre‐LCPB limestone from the Lynna River section in western Russia, that was previously studied by elemental analysis. Our study constitutes the most comprehensive oxygen isotopic data set of sediment‐dispersed extraterrestrial chrome spinel to date. We also introduce a Raman spectroscopy‐based method to identify SEC grains and distinguish them from terrestrial chrome spinel with ~97% reliability. We calibrated the Raman method with the established approach using titanium and vanadium concentrations and oxygen isotopic compositions. We find that ordinary chondrites are approximately three times more abundant in the 32–63 μm fraction than achondrites. While abundances of achondrites compared to ordinary chondrites are lower in the 32–63 μm size fraction than in the >63 μm one, achondrites are approximately three times more abundant in the 32–62 μm fraction than they are in the present flux. We find that the sources of SEC grains vary for different grain sizes, mainly as a result of parent body thermal metamorphism. We conclude that the meteorite flux composition ~467 Ma ago ~1 Ma before the breakup of the LCPB was fundamentally different from today and from other time windows studied in the Phanerozoic, but that in contrast to the large size fraction ordinary chondrites dominated the flux in the small size fraction. The high abundance of ordinary chondrites in the studied samples is consistent with the findings based on coarse extraterrestrial chrome‐spinel from other time windows. [ABSTRACT FROM AUTHOR]

Published
2024
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