^1,2,3Achen Duan,^1,4Yunzhao Wu,⁵Edward A. Cloutis,^1,2Jinfei Yu,¹Shaolin Li,^1,2Yun Jiang
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13750]
¹Key Laboratory of Planetary Sciences, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing, 210023 China
²School of Astronomy & Space Sciences, University of Science and Technology of China, Hefei, 230026 China
³Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing, 210023 China
⁴CAS Center for Excellence in Comparative Planetology, China
⁵Department of Geography, University of Winnipeg, 515 Portage Avenue, Winnipeg, R3B 2E9 Manitoba, Canada
⁶State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau, PR China
⁷CAS Center for Excellence in Comparative Planetology, China
Published by arrangement with John Wiley & Sons

Carbonaceous chondrites (CCs) are important materials for understanding the early evolution of the solar system and delivery of organic material to the early Earth. Spectral analysis of CCs can establish the relationship between them and their possible parent asteroids, which helps to determine the surface composition of the asteroid. In this paper, the 0.3–26 μm reflectance spectra of a series of coals ranging from lignite to anthracite (Earth analogs of organic matter contained in CCs), a coal heated to various durations and temperatures, and reflectance spectra of CM2 meteorites were analyzed in conjunction with compositional information to derive spectral–compositional relationships. All types of coals have strong aromatic absorptions (3.28 and 5–6.5 μm) and aliphatic “triplet” absorptions (3.38, 3.41, and 3.48 μm). In contrast, CM2 meteorites have obvious aliphatic absorptions and lack aromatic absorptions. The reason is the weak absorption coefficients of aromatic materials and the overlap with strong OH/H₂O absorption. Absorptions in the coal spectra are strongly related to elemental H/C ratio. When the H/C ratio is >0.55, the absorption intensity of an aliphatic increases linearly with the increase of H/C. For heated coal, increasing heating time above 1 h at 450 °C causes the disappearance of the aliphatic “triplet” absorptions. Similarly, heating Murchison meteorite to 400 °C for 1 week causes all the organic absorptions to disappear. This implies that in remote sensing detections, only asteroids (e.g., with CM and CI carbonaceous chondrites compositions) that experienced low thermal metamorphism (<400 °C) are suitable as potential targets for detecting organic compounds using features in the 3–4 µm region.

¹Edward D. Young
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13752]
¹Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, California, 90095 USA
Published by arrangement with John Wiley & Sons

The trapped melt fractional crystallization model for the IIIAB iron meteorites put forward by J. T. Wasson two decades prior is revisited. The basic precepts upon which the model was based remain true, and the model can be implemented using Ir and Au solid/liquid distribution coefficients that are broadly consistent with experimental data. For this reason, the difference between the Wasson model and some more recent trapped melt models lies mainly with inferences about the S concentrations of the core of the IIIAB iron meteorite parent body. For the Wasson model, S bulk concentrations of about 2 wt% are implied. For the more recent model, much greater concentrations of between about 12–15 wt% are indicated. The two different trapped melt models profoundly influence the interpretation of high δ⁵⁷Fe values relative to chondrites in the IIIAB irons. The Wasson model suggests that there should be more variations in δ⁵⁷Fe than are observed among these meteorites, while the more recent trapped melt model relies on the crystallization of FeS from the trapped melt to raise the δ⁵⁷Fe of the latter, thus minimizing the variability. The interpretation of Fe isotope ratios in the IIIAB meteorites therefore depends critically on the S concentration of the parent body core.

¹Putirka, K.D.,¹Xu, S.
Nature Communications 12, 6168 Link to Article [DOI https://doi.org/10.1038/s41467-021-26403-8]
¹Department of Earth and Environmental Sciences, California State University, 2576 E. San Ramon Ave, MS/ST 24, Fresno, CA, 93740, USA
²Gemini Observatory/NSF’s NOIR Lab, #314, 670N. A’ohoku Place, Hilo, HI, 96720, USA

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