Na, Ca carbonates in OSIRIS-REx samples: evidence for low-temperature, Na-bearing Brines on Bennu’s Parent Body

IF 4.5 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Geochimica et Cosmochimica Acta Pub Date : 2025-06-27 DOI:10.1016/j.gca.2025.06.028

S.A. Singerling, F.E. Brenker, B. Tkalcec, S.S. Russell, T.J. Zega, T.J. McCoy, H.C. Connolly Jr., D.S. Lauretta

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Abstract

We describe nanoscale observations obtained via transmission electron microscopy of Na,Ca carbonates in OSIRIS-REx samples of asteroid Bennu. Four Na,Ca carbonate grains were observed (including the one briefly described in McCoy and Russell et al., 2025), ranging in size from140 nm to 2.36 µm. The stoichiometry of the grains and electron diffraction data best match gaylussite (Na2Ca(CO3)2·5H2O) or pirssonite (Na2Ca(CO3)2·2H2O). The grains rapidly amorphized under the electron beam. We also found that the grains are reactive to the terrestrial atmosphere, with their compositions and textures changing over six months of storage in a standard desiccator. NaCl salts grew on the exteriors of the grains, and the compositions of the carbonates became richer in C, F, Cl, and Ca and poorer in O and Na

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OSIRIS-REx样品中的Na， Ca碳酸盐：本努母体内低温，含Na盐水的证据

我们描述了通过透射电子显微镜在小行星Bennu的OSIRIS-REx样品中获得的Na，Ca碳酸盐的纳米级观察结果。观察到四个Na，Ca碳酸颗粒（包括McCoy和Russell等人，2025中简要描述的一个），尺寸从140 nm到2.36 µm不等。晶粒的化学计量学和电子衍射数据最符合gaylussite （Na2Ca(CO3)2·5H2O）或pirssonite （Na2Ca(CO3)2·2H2O）。晶粒在电子束作用下迅速非晶化。我们还发现，谷物对地球大气有反应，在标准干燥器中储存六个月后，它们的成分和质地会发生变化。NaCl盐在颗粒外部生长，碳酸盐组成中C、F、Cl和Ca含量增加，O和Na含量减少

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来源期刊

Geochimica et Cosmochimica Acta 地学-地球化学与地球物理

CiteScore

9.60

自引率

14.00%

发文量

437

审稿时长

6 months

期刊介绍： Geochimica et Cosmochimica Acta publishes research papers in a wide range of subjects in terrestrial geochemistry, meteoritics, and planetary geochemistry. The scope of the journal includes: 1). Physical chemistry of gases, aqueous solutions, glasses, and crystalline solids 2). Igneous and metamorphic petrology 3). Chemical processes in the atmosphere, hydrosphere, biosphere, and lithosphere of the Earth 4). Organic geochemistry 5). Isotope geochemistry 6). Meteoritics and meteorite impacts 7). Lunar science; and 8). Planetary geochemistry.