Print button

Abstract EANA2024-19


Formation and Alteration of Macromolecular Extraterrestrial Amino Acid Precursors: Comparison with Free Amino Acids 

Kensei Kobayashi (1,2), Ibuki Ikeda (1), Soshi Kuramoto (1), Kanji Nakajima (2), Ryota Futami (1), Yoko Kebukawa (2), Isao Yoda (2), Hajime Mita (3), Hiromi Shibata (4) and Shin-ichi Yokobori (5)
(1) Yokohama National University, Japan, (2) Tokyo Institute of Technology, Japan, (3) Fukuoka Institute of Technology, Japan, (4) Kobe University, Japan (5) Tokyo University of Pharmacy and Life Sciences, Japan


Presence of amino acids in such extraterrestrial bodies as carbonaceous chondrites [1] suggested that extraterrestrial amino acids were important building blocks for the first life on the Earth. The fact that concentration of amino acids in carbonaceous chondrites increased after hydrolysis [1] showed formation of amino acid precursors in space environments.  Laboratory simulations have indicated that amino acid precursors could be synthesized in ice mantles of interstellar dust particles in molecular clouds [2] and the interior of meteorite parent bodies (MPBs) [3].  The former would have imported into meteorite parent bodies. It was suggested that cosmic dusts would have delivered more organics than meteorites and comets [4].

Here we examined what types of amino acid precursors were formed in extraterrestrial bodies, and compared their stability in extraterrestrial environments (e.g., in interior of meteorite parent bodies and interplanetary space) with that of free amino acids.

Characterization of amino acid precursors: A mixture of CO, NH3 and H2O was irradiated with high energy protons to simulate reactions in molecular clouds (the product: hereafter referred to as CAW). CAW contained not free amino acids, but amino acid precursors.  It was proved that the most of amino acid precursors formed were not conventional simple glycine precursors like aminoacetonitrile nor hydantoin, but macromolecular ones whose molecular weights estimated to be thousands.  

Stability of CAW and free amino acids in MPBs and in Low Earth Orbit (LEO): CAW and free amino acids were dissolved in aqueous solution of HCHO, CH3OH and NH3, and irradiated with gamma-rays from a 60Co source, and their recovery was examined (CAW was acid-hydrolyzed before analysis).  Among free amino acids, glycine was more stable than more complex amino acids (e.g., valine).  CAW was more stable as glycine precursor than free glycine.  Besides decomposition of original glycine or CAW, various amino acids were newly formed by gamma-irradiation. CAW yielded more novel amino acids than glycine in simulated meteorite parent body interior environment.  Newly formed amino acid precursors were proved to be macromolecular ones, but their molecular weights were lower than CAW.

We examined the stability of glycine and macromolecular amino acid precursors (MAAPs) in LEO by utilizing the International Space Station.  In the Tanpopo mission, glycine and CAW showed almost the same stability, where shorter UV was cut with MgF2 window and hexatriacontane film [5].  In the Tanpopo2 mission, MAAPs were more stable than free glycine, where they were directly exposed to space without windows nor film [6]. In LEO, presence of atomic oxygen might have an effect on the stability.  In order to simulate behavior of organics in deep space, further space experiments utilizing facilities like the Lunar Orbital Platform-Gateway.

  1. D. P. Glavin et al. (2020) Chem. Rev. 120, 4660.
  2. T. Kasamatsu et al. (1997) Bull. Soc. Chem. Jpn. 70, 1021.
  3. Y. Kebukawa et al. (2022) ACS Cent. Sci. 8, 1864. 
  4. C. Chyba and C. Sagan (1992) Nature 355, 125.
  5. K. Kobayashi et al. (2021) Astrobiology 21, 1479.
  6. K. Kobayashi et al. (2023) EANA 2023.