Abstract EANA2025-144

Sugars, nucleobases and amino acids are the fundamental building blocks of nucleic acids, proteins and polysaccharides, the three fundamental biopolymers of life. The exogeneous, or "top-down", hypothesis suggests that meteorites delivered these and other key biomolecules to early Earth, overcoming environmental and time constraints for life’s rapid emergence on Earth [1] and potentially explaining life’s chiral bias [2]. However, while amino acids and nucleobases are well-documented in several carbonaceous chondrites [3] and, most recently, in Bennu and Ryugu asteroid samples [4], sugars remain poorly characterized, with only one study confirming their presence in meteorites [5]. This contrasts with interstellar ice experiments predicting widespread sugar formation in space [6], highlighting a key gap in assessing meteorites as a relevant source of sugars for prebiotic chemistry.

The scarce report of sugars in meteorites has traditionally been attributed to degradation processes in space or within mineral matrices [7]. However, analytical challenges in recovery and detection-a critical factor that remains understudied-may represent an equally significant limitation. Establishing the extraterrestrial origin of soluble organics requires both pristine laboratory conditions and extraction of compounds at concentrations sufficient for either isotopic characterization or robust enantiomeric analysis [3]. While isotopic analysis showing enrichment on ¹³C, ¹⁵N, and D, provides the most definitive evidence of extraterrestrial origin [8], this approach typically demands sample quantities that are impractical for most extraterrestrial materials [9]. When sample mass is limited, enantiomeric excess measurements provide a persuasive alternative for contamination assessment [2,3,4]. This is due to life's strict chiral preferences for specific enantiomers-l-amino acids in proteins and d-sugars in nucleic acids-where near-racemic ratios or non-biological enantiomeric excesses strongly indicate abiotic, and potentially extraterrestrial, origins.

In this study, we report the first identification and enantiomeric resolution of two C5 sugars (arabinose and xylose) in Ryugu aggregate samples, along with the complete suite of aldopentoses and ribulose in the Orgueil carbonaceous meteorite. Our novel analytical workflow enables the simultaneous enantioselective analysis of both chiral amino acids and sugars from the same extracts, achieving two key objectives: (i) validating our methodology through direct comparison with previous analyses of Ryugu and Orgueil samples, and (ii) revealing distinct distribution patterns between sugars and amino acids in extraterrestrial materials. The detection of near-racemic ratios for multiple compounds strongly supports their abiotic origin, providing compelling evidence that meteorites served as delivery vehicles for prebiotic molecules crucial to life's origins.

References

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