Influx of nitrogen-rich material from the outer Solar System indicated by iron nitride in Ryugu samplesOPEN ACCESS 

Toru Matsumoto, Takaaki Noguchi, Akira Miyake, Yohei Igami, Mitsutaka Haruta, Yusuke Seto, Masaaki Miyahara, Naotaka Tomioka, Hikaru Saito, Satoshi Hata, Dennis Harries, Aki Takigawa, Yusuke Nakauchi, Shogo Tachibana, Tomoki Nakamura, Megumi Matsumoto, Hope A. Ishii, John P. Bradley, Kenta Ohtaki, Elena Dobrică, Hugues Leroux, Corentin Le Guillou, Damien Jacob, Francisco de la Peña, Sylvain Laforet, Maya Marinova, Falko Langenhorst, Pierre Beck, Thi H. V. Phan, Rolando Rebois, Neyda M. Abreu, Jennifer Gray, Thomas Zega, Pierre-M. Zanetta, Michelle S. Thompson, Rhonda Stroud, Kate Burgess, Brittany A. Cymes, John C. Bridges, Leon Hicks, Martin R. Lee, Luke Daly, Phil A. Bland, Michael E. Zolensky, David R. Frank, James Martinez, Akira Tsuchiyama, Masahiro Yasutake, Junya Matsuno, Shota Okumura, Itaru Mitsukawa, Kentaro Uesugi, Masayuki Uesugi, Akihisa Takeuchi, Mingqi Sun, Satomi Enju, Tatsuhiro Michikami, Hisayoshi Yurimoto, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Sei-ichiro Watanabe & Yuichi Tsuda

Nature Astronomy
Published: 30 November 2023

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“Large amounts of nitrogen compounds, such as ammonium salts, may be stored in icy bodies and comets, but the transport of these nitrogen-bearing solids into the near-Earth region is not well understood. Here, we report the discovery of iron nitride on magnetite grains from the surface of the near-Earth C-type carbonaceous asteroid Ryugu, suggesting inorganic nitrogen fixation. Micrometeoroid impacts and solar wind irradiation may have caused the selective loss of volatile species from major iron-bearing minerals to form the metallic iron. Iron nitride is a product of nitridation of the iron metal by impacts of micrometeoroids that have higher nitrogen contents than the CI chondrites. The impactors are probably primitive materials with origins in the nitrogen-rich reservoirs in the outer Solar System. Our observation implies that the amount of nitrogen available for planetary formation and prebiotic reactions in the inner Solar System is greater than previously recognized.”