Extraterrestrial Amino Acids and Amines Identified in Asteroid Ryugu Samples Returned by theHayabusa2 Mission
Eric T. Parker1, Hannah L. McLain1,2,3, Daniel P. Glavin1, Jason P. Dworkin1, Jamie E. Elsila1, José C. Aponte1,2,3, Hiroshi
Naraoka4, Yoshinori Takano5, Shogo Tachibana6,
The Hayabusa2-initial-analysis SOM team, The Hayabusa2- initial-analysis core1
Astrobiology Analytical Laboratory, Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, MD
20771, U.S.A.
2Center for Research and Exploration in Space Science and Technology (CRESST), NASA Goddard Space Flight Center,Greenbelt, MD 20771, U.S.A.; 3Department of Physics, The Catholic University of America, Washington, D.C. 20064, U.S.A.;
4Department of Earth and Planetary Science, Kyushu University, Nishi-ku, Fukuoka, 819-0395, Japan; 5Biogeochemistry
Research Center (BGC), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Kanagawa, 2370061, Japan; 6UTokyo Organization for Planetary and Space Science (UTOPS), The University of Tokyo, 7-3-1 Hongo, Tokyo
113-0033, Japan
Analyses of amino acids and aliphatic amines were performed on the hot water extracts of two asteroid Ryugu
samples returned by the JAXA Hayabusa2 mission. The two samples were A0106, which was comprised of surface material,
and C0107, which was comprised of both surface and possible subsurface material. Prior to amino acid analysis, portions ofeach sample extract underwent acid vapor hydrolysis, while other portions remained unhydrolyzed to allow for a respective
comparison between bound and free amino acids. Subsequently, these extracts were derivatized with o-phthaldialdehyde/Nacetyl-L-cysteine, a chiral, fluorescent tag that enhances analytical specificity and sensitivity for primary amines, and thenanalyzed using ultrahigh performance liquid chromatography with fluorescence detection and high-resolution massspectrometry. Prior to the analysis of aliphatic amines, separate portions of each sample extract were derivatized withAccQ•Tag, a florescent tag that is insensitive to salts and targets primary amines and select secondary amines, and thenanalyzed by ultraperformance liquid chromatography with fluorescence detection and time-of-flight mass spectrometry. The
analyses performed here focused on the abundances and relative distributions of amino acids and aliphatic amines, as well as
determining the enantiomeric compositions of detected chiral amino acids. For contamination control and backgroundsubtraction purposes, procedural and analytical blanks were processed and analyzed in parallel with the Ryugu samples.
In total, 13 amino acids were detected and quantitated here. Five additional amino acids were tentatively identified,but not quantitated. Abundances of individual amino acids of the C2 – C6 variety were measured to vary between 0.02 and 15.8
nmol g-1. Among those amino acids identified, several were non-protein amino acids that are uncommon in biology. These
included β-aminoisobuytric acid (β-AIB) and β-amino-n-butyric acid (β-ABA), which were measured to be racemic or very
nearly racemic, suggesting that these species were likely to be indigenous to the sample and extraterrestrial in nature. While
trace quantities of select protein amino acids were found to be enriched in the L-enantiomer, elevated abundances of racemic,
free alanine were observed, indicating that the Ryugu sample studied here were exposed to minimal terrestrial contamination.
The analyses of aliphatic amines revealed four species of the C1 – C3 variety, which were identified and measured
above background levels. These aliphatic amines were methylamine, ethylamine, isopropylamine, and propylamine, in order ofdescending abundances. These aliphatic amine species were individually measured at abundances ranging from 0.05 – 34.14
nmol g-1 in the unhydrolyzed hot water extracts of Ryugu samples A0106 and C0107.
It has been reported that Ryugu samples are chemically similar to CI-type chondrites [1,2]. However, the abundancesand relative distributions of amino acids and aliphatic amines in Ryugu are strikingly different from those of CI1.1/2.0 Orgueil.
More specifically, CI1.1/2.0 Orgueil contains upwards of 5.6x the total abundance of amino acids as Ryugu, and more than 5x
the total abundance of aliphatic amines as Ryugu. These observed abundance differences could be caused by discrepancies inalteration conditions experienced by the parent bodies of Orgueil and Ryugu, or variabilities in original parent body chemical
conditions. Additionally, it is plausible the lower overall abundances of amino acids and amines in the near-surface samples
collected by Ryugu may be due to the loss of these compounds, or their volatile precursors, via such factors as space
weathering and solar heating in a hard vacuum environment. These possible loss mechanisms are worthy of further exploration.
Regarding amino acid distributions observed in Ryugu, α-amino acids, which could have been generated by the Strecker
cyanohydrin synthesis, were identified, along with β-, γ-, and δ-amino acids. Examples of the latter included C3 – C5 straightchain n-ω-amino acids. The observed amino acid distribution indicates that more than one formation mechanism occurred on
the Ryugu parent body and was responsible for the amino acids reported here. Lastly, the analytical techniques used here weresufficiently sensitive to detect and quantify the target analytes under the limited sample mass conditions of the current work,
which offers strong evidence that these methods will likely perform similarly well when applied to the analyses of amino acids
and aliphatic amines in asteroid Bennu samples returned by the NASA OSIRIS-REx mission in September 2023.

References[1] Yada, T. et al. (2022) Nature Astronomy, 6, 214-220. [2] Yokoyama, T. et al. (2022) Science, eabn7850.
The Hayabusa2-initial-analysis SOM team: Hiroshi Naraoka, Yoshinori Takano, Jason P. Dworkin, Kenji Hamase, Aogu
Furusho, Minako Hashiguchi, Kazuhiko Fukushima, Dan Aoki, José C. Aponte, Eric T. Parker, Daniel P. Glavin, Hannah L.
McLain, Jamie E. Elsila, Heather V. Graham, John M. Eiler, Philippe Schmitt-Kopplin, Norbert Hertkorn, Alexander Ruf,
Francois-Regis Orthous-Daunay, Cédric Wolters, Junko Isa, Véronique Vuitton, Roland Thissen, Nanako O. Ogawa, SaburoSakai, Toshihiro Yoshimura, Toshiki Koga, Haruna Sugahara, Naohiko Ohkouchi, Hajime Mita, Yoshihiro Furukawa,Yasuhiro Oba, Yoshito Chikaraishi.
The Hayabusa2-initial-analysis core: Shogo Tachibana, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, RyujiOkazaki, Kanako Sakamoto, Hikaru Yabuta, Hisayoshi Yurimoto, Yuichi Tsuda, Sei-ichiro Watanabe.