Non‐protein amino acids identified in carbon‐rich Hayabusa particles

Abstract

Amino acid abundances in acid-hydrolyzed hot water extracts of gold foils containing five Category 3 (carbon-rich) Hayabusa particles were studied using liquid chromatography with tandem fluorescence and accurate mass detection. Initial particle analyses using field emission scanning electron microscopy with energy-dispersive X-ray spectrometry indicated that the particles were composed mainly of carbon. Prior to amino acid analysis, infrared and Raman microspectroscopy showed some grains possessed primitive organic carbon. Although trace terrestrial contamination, namely L-protein amino acids, was observed in all Hayabusa extracts, several terrestrially uncommon non-protein amino acids were also identified. Some Hayabusa particles contained racemic (D≈L) mixtures of the non-protein amino acids β-aminoisobutyric acid (β-AIB) and β-amino-n-butyric acid (β-ABA) at low abundances ranging from 0.09 to 0.31 nmol g −1 . Larger abundances of the non-protein amino acid β-alanine (9.2 nmol g −1 , ≈4.5 times greater than background levels) were measured in an extract of three Hayabusa particles. This β-alanine abundance was ≈6 times higher than that measured in an extract of a CM2 Murchison grain processed in parallel. The comparatively high β-alanine abundance is surprising as asteroid Itokawa is similar to amino acid-poor LL ordinary chondrites. Elevated β-alanine abundances and racemic β-AIB and β-ABA in Hayabusa grains suggested these compounds have nonbiological and plausibly non-terrestrial origins. These results are the first evidence of plausibly extraterrestrial amino acids in asteroid material from a sample-return mission and demonstrate the capabilities of the analytical protocols used to study asteroid Ryugu and Bennu samples returned by the JAXA Hayabusa2 and NASA OSIRIS-REx missions, respectively.

Aqueous breakdown of aspartate and glutamate to n-ω-amino acids on the parent bodies of carbonaceous chondrites and asteroid Ryugu

“…Such discrimination is important for clarifying the origin of these n-ω-amino acids on various extraterrestrial samples. For instance, some of the return samples from asteroid Itokawa brought by the Hayabusa mission has been found to contain amino acids enriched with β-Ala and γ-ABA with aqueous alteration characteristics ( 104 ). The fact that Itokawa is compositionally similar to LL5 and LL6 ordinary chondrites suggests that these amino acids probably originated from exogenous material delivered from another carbon-rich body ( 104 ).…”

“…For instance, some of the return samples from asteroid Itokawa brought by the Hayabusa mission has been found to contain amino acids enriched with β-Ala and γ-ABA with aqueous alteration characteristics ( 104 ). The fact that Itokawa is compositionally similar to LL5 and LL6 ordinary chondrites suggests that these amino acids probably originated from exogenous material delivered from another carbon-rich body ( 104 ). The enrichment mechanism can be further clarified on the basis of the reaction network demonstrated in this study.…”

Astrobiology in Space: A Comprehensive Look at the Solar System

“…The Stardust mission targeted Comet Wild 2 and found evidence of extraterrestrial glycine [ 53 ]. Similarly, the Hayabusa mission found (non-proteogenic) amino acids on asteroid 25,143 Itokawa [ 54 ]. As a result of its success, JAXA extended the mission and sent Hayabusa2 to asteroid 162,173 Ryugu where it also collected and returned samples.…”

Ion irradiation triggers the formation of the precursors of complex organics in space

“…Complex organics are also found in materials sampled from asteroids (e.g. Chan et al 2021;Pilorget et al 2021;Parker et al 2022), in interplanetary dust particles (IDPs; e.g. Chan et al 2020) and carbonaceous chondrites (CC; e.g.…”