^1,2Iori Kajitani,³Mizuho Koike,⁴Ryoichi Nakada,⁵Gaku Tanabe,^2,6Tomohiro Usui,⁷Fumihiro Matsu’ura,⁸Keisuke Fukushi,⁵Tetsuya Yokoyama
Earth and Planetary Science Letters 620, 118345 Link to Article [https://doi.org/10.1016/j.epsl.2023.118345]
¹Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo. 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
²Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency. 3-1-1 Yoshinodai, Sagamihara, Kanagawa 252-5210, Japan
³Earth and Planetary Systems Science Program, Department of Advanced Science and Engineering, Hiroshima University. 1-3-1 Kagamiyama, Higashihiroshima, Hiroshim 739-8526, Japan
⁴Kochi Institute for Core Sample Research, Institute for Extra-cutting-edge Science and Technology Avant-garde Research (X-star), Japan Agency for Marine-Earth Science and Technology (JAMSTEC). 200 Monobe, Nankoku, Kochi 783-8502, Japan
⁵Department of Earth and Planetary Sciences, School of Science, Tokyo Institute of Technology. 2-12-1 Ookayama, Meguro, Tokyo 152-8550, Japan
⁶Earth-Life Science Institute, Tokyo Institute of Technology. 2-12-1 Ookayama, Meguro, Tokyo 152-8550, Japan
⁷International Center for Isotope Effects Research, Nanjing University, Nanjing, Jiangsu Province 210023, China
⁸Institute of Nature and Environmental Technology, Kanazawa University, Kanazawa, Ishikawa, Japan
Copyright Elsevier

The aqueous environment and possible habitability of early Mars have been widely studied based on orbital and in situ explorations, as well as analyses of Martian meteorites. Using microscale X-ray absorption near edge structure (μ-XANES) analysis, we report the first sulfur (S) speciation of the carbonates in a Martian meteorite, Allan Hills 84001, precipitated in the 4-billion-year-old aqueous alteration on Mars. The XANES data show diagnostic signatures of oxidized sulfur in the carbonates, indicating that carbonate-associated sulfate (CAS) formed from coexisting sulfate ions (SO
) in the aqueous fluid. A thermodynamic calculation suggests that the CAS deposited from a fluid with a moderately oxidizing to reducing and neutral to slightly alkaline pH condition. The possible sources of SO
ions are the minor SOx species in the Noachian atmosphere and/or the supply from volcanic gas. It is concluded that considerable amounts of the atmospheric volatiles including CO2 and SOx may have been stored as alteration products (e.g., carbonates) in the Martian underground system.