This paper reports the discovery of primordial aqueous alteration signatures in water-soluble organic molecules from the carbonaceous asteroid (162173) Ryugu. Low-molecular-weight hydroxy acids and dicarboxylic acids, such as glycolic acid, lactic acid, and oxalic acid, are prevalent in samples. The presence of malonic acid, particularly sensitive to keto-enol tautomerism, suggests substantial aqueous alteration. The findings provide evidence for coevolutionary aqueous alteration between water and organics on this asteroid.

Yoshinori Takano, Hiroshi Naraoka, Jason P. Dworkin, Toshiki Koga, Kazunori Sasaki, Hajime Sato, Yasuhiro Oba, Nanako O. Ogawa, Toshihiro Yoshimura, Kenji Hamase, Naohiko Ohkouchi, Eric T. Parker, José C. Aponte, Daniel P. Glavin, Yoshihiro Furukawa, Junken Aoki, Kuniyuki Kano, Shin-ichiro M. Nomura, Francois-Regis Orthous-Daunay, Philippe Schmitt-Kopplin, Hisayoshi Yurimoto, Tomoki Nakamura, Takaaki Noguchi, Ryuji Okazaki, Hikaru Yabuta, 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, Shogo Tachibana