In situ investigation of an organic micro‐globule and its mineralogical context within a Ryugu “sand” grain
Authors: Phan Van T. H. , Beck Pierre , Rebois Rolando , Quirico Eric , Noguchi Takaaki , Matsumoto Toru , Miyake Akira , Igami Yohei , Haruta Mitsutaka , Saito Hikaru , Hata Satoshi , Seto Yusuke , Miyahara Masaaki , Tomioka Naotaka , Ishii Hope A. , Bradley John P. , Ohtaki Kenta K. , Dobrică Elena , Leroux Hugues , Le Guillou Corentin , Jacob Damien , de la Peña Francisco , Laforet Sylvain , Marinova Maya , Langenhorst Falko , Harries Dennis , Abreu Neyda M. , Gray Jennifer , Zega Thomas , Zanetta Pierre‐M. , Thompson Michelle S. , Stroud Rhonda , Mathurin Jérémie , Dazzi Alexandre , Dartois Emmanuel , Engrand Cécile , Burgess Kate , Cymes Brittany A. , Bridges John C. , Hicks Leon , Lee Martin R. , Daly Luke , Bland Phil A. , Zolensky Michael E. , Frank David R. , Martinez James , Tsuchiyama Akira , Yasutake Masahiro , Matsuno Junya , Okumura Shota , Mitsukawa Itaru , Uesugi Kentaro , Uesugi Masayuki , Takeuchi Akihisa , Sun Mingqi , Enju Satomi , Takigawa Aki , Michikami Tatsuhiro , Nakamura Tomoki , Matsumoto Megumi , Nakauchi Yusuke , Abe Masanao , Nakazawa Satoru , Okada Tatsuaki , Saiki Takanao , Tanaka Satoshi , Terui Fuyuto , Yoshikawa Makoto , Miyazaki Akiko , Nakato Aiko , Nishimura Masahiro , Usui Tomohiro , Yada Toru , Yurimoto Hisayoshi , Nagashima Kazuhide , Kawasaki Noriyuki , Sakamotoa Naoya , Hoppe Peter , Okazaki Ryuji , Yabuta Hikaru , Naraoka Hiroshi , Sakamoto Kanako , Tachibana Shogo , Watanabe Sei‐ichiro , Tsuda Yuichi 
Published: January 2024

AbstractThe Hayabusa2 mission from the Japan Aerospace Exploration Agency (JAXA) returned to the Earth samples of carbonaceous asteroid (162173) Ryugu. This mission offers a unique opportunity to investigate in the laboratory samples from a C‐type asteroid, without physical or chemical alteration by the terrestrial atmosphere. Here, we report on an investigation of the mineralogy and the organo‐chemistry of Hayabusa2 samples using a combination of micro‐ and nano‐infrared spectroscopy. Particles investigated with conventional FTIR spectroscopy have spectra dominated by phyllosilicate‐related absorption, as observed for samples of CI‐chondrites, selected ungrouped carbonaceous chondrites, and selected hydrated micrometeorites. Ryugu samples show smaller sulfate‐related absorption than CI‐chondrites. Our samples that were only briefly exposed to the Earth atmosphere show absorptions related to molecular water, revealing fast terrestrial contamination of the spectral signature at 3 μm. Overall, our FTIR data are in agreement with other work done on Ryugu samples, revealing a low degree of mineralogical variability across Ryugu samples. AFM‐IR mapping of the grains shows the presence of a micrometer‐sized organic globule in one of our analyzed grains. The AFM‐IR spectra obtained on this globule are similar to IR spectra obtained on IOM suggesting that it is constituted of refractory organic matter. This globule may host silicate in its interior, with a different mineralogy than bulk Ryugu phyllosilicate. The shape, presence of peculiar silicate, and the nature of organic constituting the globule point toward a pre‐accretionary origin of this globule and that at least part of Ryugu organics were inherited from the protosolar nebulae or the interstellar media. Altogether, our results show the similarities between Ryugu samples and CI chondrites.