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 non‐biological 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.

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

High precision 26Al-26Mg chronology of chondrules in unequilibrated ordinary chondrites: evidence for restricted formation ages

The H2O content of the ureilite parent body

Exsolution in alkali feldspar in ordinary chondrites: Ubiquitous evidence for rapid cooling at high temperatures

Meteorites preserve evidence of processes on their parent bodies, including alteration, metamorphism, and shock events. Here we show that the Kakowa (L6) ordinary chondrite (OC) preserves both shock-melt veins and pockets of detrital grains from a brecciated and altered object, including corundum, albite, silica, fayalite, forsterite, and margarite in a Pb- and Fe-rich matrix. Preservation of the observed mineralogy and texture requires a sequence of at least two impacts: first, a high-velocity collision formed the shock melt veins containing the high-pressure minerals ringwoodite, wadsleyite, majorite, and albitic jadeite; later, a low-velocity impact formed fractures and filled them with the detrital material. Oxygen and Pb isotope ratios suggest an OC origin for these detrital minerals. Although fluid alteration is common in carbonaceous chondrites, the discovery of margarite with an OC oxygen isotopic signature is novel. Kakowa extends both the impact and alteration history of L6 ordinary chondrites in general. 

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Daljit Roy Banger

Papers

Plagioclase alteration and equilibration in ordinary chondrites: Metasomatism during thermal metamorphism

Plagioclase alteration and equilibration in ordinary chondrites: Metasomatism during thermal metamorphism

Exsolution in alkali feldspar in ordinary chondrites: Ubiquitous evidence for rapid cooling at high temperatures