Abiotic sugar enantiomers in the CI carbonaceous chondrite Orgueil

Domain: neuroscience
Published: 2026-01-27
Editorial outcome: major_revision

Abstract
The uneventful detection of prebiotic organic compounds in meteorites—where amino acids and nucleobases are commonly identified but sugars remain rare and poorly characterized—limits our understanding of extraterrestrial organic chemistry. This discrepancy is striking given that laboratory simulations of interstellar ice chemistry readily produce complex sugars. Here we report the simultaneous analysis of sugar and amino acid enantiomers in a meteorite sample. Multiple aldoses were detected in the Orgueil meteorite, including ribose, arabinose, xylose, lyxose, and the ketopentose ribulose, several of which display near-racemic distributions consistent with an extraterrestrial origin. Recovery experiments demonstrate that sugar abundances are severely underestimated. Despite this limitation, pentose abundances are comparable to those of some C4–C5 amino acid enantiomers, implying higher true concentrations. These results indicate efficient abiotic sugar formation in space and suggest that meteorites may have delivered a broader range of prebiotically relevant sugars to early Earth than previously recognized.

Introduction
Nucleic acids (RNA, DNA), composed of sugars, nucleobases, and phosphates, and proteins, built from amino acids, are the fundamental biopolymers of life. A central question concerning the origin of life on Earth is how these essential biomolecular building blocks were synthesized, concentrated, and assembled into biopolymers, given their fragile nature, the planet’s extreme and fluctuating environmental conditions1–3 and the brief timescale for life’s emergence following Earth’s consolidation4. One plausible source of these biomolecular precursors to the terrestrial prebiotic inventory, strongly supported by both astronomical and geological evidence, is their exogenous delivery via extraterrestrial bodies such as interplanetary dust particles and meteorites1,5–10, supplementing the local prebiotic synthesis on early Earth.

However, while amino acids and nucleobases have been repeatedly detected in various carbonaceous chondrites11–14 and, more recently, in samples from the asteroids Ryugu15–17 and Bennu18, the detection of sugars—essential as components of nucleic acids but also as monomers of structural and energy‑storage polymers in all living organisms—remains remarkably scarce. To date, only a single study by Furukawa et al.19 has confirmed the presence of ribose and other aldopentoses in meteorite samples, highlighting the current limitations in our ability to detect and understand sugar inventories in extraterrestrial materials. Moreover, the relatively large sample masses required in that study (~2 g) further constrain the applicability of such analyses to scarce pristine materials such as those returned from asteroids (Ryugu, total=5.4 g; Bennu, 121.6 g). However, sugars and sugar-related compounds have recently been identified in powdered aliquots of regolith returned from asteroid Bennu by the OSIRIS-REx mission20 (OREX-800107-108; 603.4 mg), demonstrating that such compounds can be detected in substantially smaller masses of pristine asteroidal material. Nevertheless, the paucity of data on extraterrestrial sugars contrasts sharply with numerous laboratory studies on interstellar ice21–24 and planetary or parent body mineral analogs25–27, which predict the widespread formation of a diverse range of C3 to C6 aldose sugars under extraterrestrial conditions. Moreover, glycolaldehyde, a potential precursor of larger carbohydrates, has been previously detected in the interstellar medium towards the Galactic center source Sagittarius B2(N)28 as well as on comet 67P/Churyumov-Gerasimenko29. From a prebiotic chemistry perspective, investigating the presence, abundance, and formation mechanisms of sugars under astrophysical conditions is a critical objective. Indeed, the potential delivery of sugars like ribose via meteorites could have provided a sustained source for the formation of primitive nucleotides in environments such as warm little ponds that may have facilitated their stabilization through rapid polymerization2. This is particularly significant given the inherent instability of sugars in aqueous environments6,30–33, where rapid degradation could otherwise limit their role in early biochemical pathways. The apparent scarcity of sugars in extraterrestrial samples has been attributed to their potential chemical transformation in space or within the meteorite mineral matrix, where they may be converted into sugar alcohols or sugar acids34. In addition, strong matrix effects—particularly the entrapment of sugars within clay mineral phases—could significantly reduce extraction efficiencies35,36.

A major challenge in analyzing prebiotically relevant organics such as amino acids and sugars from astrophysical samples lies in confirming their extraterrestrial origin, due to the ever-present risk of terrestrial contamination. While meteorites are often subject to terrestrial weathering and potential microbial colonization prior to analysis37,38, even returned samples—such as those from (162173) Ryugu and (101955) Bennu, despite being collected under meticulously controlled conditions by the JAXA’s Hayabusa2 and NASA’s OSIRIS-REx missions38–41 require meticulous handling and verification protocols to confidently assess indigenous organics. Contamination risks remain particularly relevant during post-collection sample processing37. Stable isotope ratios provide a powerful tool for addressing this issue, as they yield insights into the formation pathways and environmental conditions of organic compounds. Importantly, they can help distinguish biological from abiotic origins, since extraterrestrial organics are typically enriched in heavy isotopes relative to their terrestrial counterparts11,42. Notably, chiral amino acids found in meteorites have been found to be enriched in the heavy isotopes 13C, 15N, and D (deuterium)43–45. Similarly, the 13C isotopic enrichment of the detected sugars in Murchison (CM2) and NWA 801 (CR2) meteorites was used to support their extraterrestrial origin19. However, the feasibility and precision of compound-specific isotopic measurements are significantly constrained by the need for high analyte concentrations, requiring large sample sizes46. This constraint makes isotopic analysis of soluble organics impossible for many relevant extraterrestrial samples, for which very limited sample material is available. Furthermore, since isotopic measurements depend on prior chromatographic separations, the sample preparation process can introduce additional losses and analytical biases, further compromising the reliability of the measurements46. In particular, in the only confirmed detection of sugars in meteorites, Furukawa et al.19 reported that the accuracy of the carbon isotope measurements for arabinose in NWA 801 was limited by a significant co-eluting peak, preventing reliable δ13C determination.

As a result of this limitation, enantiomeric excess measurements of chiral organics have increasingly become crucial for evaluating terrestrial contamination, particularly in samples of limited mass available for analysis13,38. The molecular architecture of life on Earth is defined by a striking preference for specific chiral configurations—such as L-amino acids in proteins and D-sugars in nucleic acids—therefore, near-racemic mixtures or the presence of non-biological enantiomers suggest abiotic, and potentially extraterrestrial, origins.

In this study, we report the detection and enantiomeric separation of all four aldopentoses and ribulose, a ketopentose, in a fragment of the Orgueil carbonaceous meteorite weighing only 178 mg. Our analysis combined ultrasound-assisted extraction, ion-exchange chromatography for fractionation and purification, with enantioselective comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC–TOF‑MS)47,48. The differences in enantiomeric distributions between the detected sugars and the procedural blanks, along with the near-racemic distribution of ribulose, provide evidence supporting their possible extraterrestrial origin.

Critically, enantiomeric resolution was essential for confirming the origin of the detected sugars, as the limited quantities targeted precluded isotopic analysis. Our findings challenge the widely held assumption that sugars are significantly less abundant than amino acids in carbonaceous chondrites. Incorporating compound-specific recovery rates indicates that the estimated quantities of individual sugar enantiomers are at least comparable to those of C4–C5 amino acid enantiomers in the same samples. These results support the hypothesis that meteorites delivered not only amino acids and nucleobases but also appreciable amounts of prebiotic sugars to early Earth—bridging a critical gap between their abiotic synthesis in interstellar ices and their potential role in the emergence of early biochemical systems.

Results
To characterize the sugar and amino acid content of the Orgueil sample while minimizing the degradation of labile organics, we developed an analytical workflow combining sequential extraction, fractionation, and derivatization steps optimized for the simultaneous recovery and separate enantioselective analysis of both compound classes (Fig. 1). Key to this methodology is a mild extraction protocol employing ultrasonic-assisted extraction (temperature <20 °C, neutral pH, and 10-min sonication intervals) to prevent thermal degradation of sugars32. An ion exchange chromatography (IEC) step was employed to remove inorganic ions (e.g., Fe2+, Fe3+, and Mg2+)—major components of chondritic mineral matrices that interfere with subsequent derivatization and chromatographic protocols49,50—and to separate neutral sugars from amino acid zwitterions49. This separation allows for tailored derivatization procedures and chromatographic conditions specific to each molecular class, enhancing both sensitivity and selectivity in their analyses. A detailed description of the sample preparation, extraction procedure, and chromatographic measurements is in the “Methods” section.

Detection of ribulose and aldopentoses in Orgueil
Building on the reported inverse relationship between sugar-related compound abundance and carbon number reported by Cooper et al.34, we focused on the detection of C3 to C5 sugar aldoses, including glyceraldehyde, erythrose, ribose, 2-deoxyribose, lyxose, arabinose, xylose, as well as the C5 ketose ribulose. These compounds were targeted as methylboronic acid derivatives using GC×GC–TOF-MS, chosen for its high enantiomeric resolution power and detectability47. Despite the limited sample quantity of 178.3 mg of meteorite material and the challenges associated with the extraction and analysis of sugars from extraterrestrial samples we unambiguously detected all four C5 aldoses at concentrations above procedural blank levels (Fig. 2, Supplementary Fig. 4). A detailed comparison of sugar enantiomers in the Orgueil sample and procedural blanks is provided in Supplementary Figs. 4–5 alongside their corresponding mass spectra (Supplementary Figs. 6–9). Arabinose and xylose detected in Orgueil exhibited much stronger biases towards the biologically abundant enantiomers L-arabinose and D-xylose, likely resulting at least partly from terrestrial contamination accumulated over the long curation history of this CI meteorite51. In contrast to arabinose and xylose, the prebiotically significant sugar ribose and its rare stereoisomer lyxose were both detected in nearly racemic proportions (Fig. 2), suggesting an abiotic origin.

Enantiomeric excess (ee) data for arabinose and xylose in the Orgueil sample are reported in Table 1. For the other detected sugars, rapid degradation of their derivatives in the presence of residual matrix material (Supplementary Fig. 10) hindered replicate analyses, rendering the corresponding ee values indicative rather than statistically robust. The %ee calculations were based on the peak areas of both enantiomers in the single ion chromatograms to minimize uncertainties associated with calibration curves, such as the conversion from ion counts to ppb. Moreover, matrix effects likely cause different slopes between standard and meteoritic sample curves, potentially leading to inaccurate concentrations. The same approach was applied for the amino acids reported below.

We also report the detection of the C5 ketose ribulose, found in near-racemic proportions. Figure 3 shows the GC×GC chromatograms and corresponding mass spectra of the ribulose enantiomers, along with procedural blanks and reference standards for comparison.

The concentrations of sugars measured in the Orgueil sample ranged from 0.1 to 6.8 ppb, corresponding to approximately 0.67 to 45 pmol/g (Table 1). Arabinose and xylose concentrations were 2–3 orders of magnitude lower than those reported for the CM2 meteorite Murchison by Furukawa et al.19. However, because the reported isotopic ratio of Murchison xylose (δ13C ≈ −1 ± 4‰) falls only slightly outside the terrestrial range (−32 to −1‰) and its abundance is relatively high compared with other sugars, a terrestrial contribution to the observed xylose signal cannot be fully excluded, particularly in the absence of enantiomeric resolution. Given the very limited dataset on meteoritic sugars, it is premature to attribute the apparent differences in sugar abundances between CI and CM chondrites to variations in parent-body histories or mineral compositions. Comparison of aldopentose distributions between Orgueil and Bennu20 reveals some quantitative differences that likely reflect either distinct parent-body processing histories or variations in matrix effects during extraction. Lyxose abundances are of the same order of magnitude in both samples, while ribose appears slightly less abundant in Orgueil; these comparisons do not yet account for the low recovery rates in our analyses (~20% for lyxose and ~5% for ribose). In contrast, arabinose and xylose show more substantial differences between Orgueil and Bennu.

To better constrain the origin of the detected sugars, we conducted a detailed assessment of potential contamination sources in our procedural blanks. We compared sugar levels in the reagent blank with those in procedural blanks prepared without and with the SiO2 matrix, which indicated that the major contribution to contamination arose during the derivatization step, specifically from the derivatization reagents (Supplementary Note 2, Supplementary Fig. 4). Moreover, spiking experiments with several milligrams of a previously extracted Orgueil sample revealed a pronounced suppression of sugar recovery in the presence of a CI-type meteorite matrix (Supplementary Note 3), with recovery rates ranging from approximately 1% for ribulose to 30% for arabinose. Notably, these compound-specific recovery efficiencies align with the aldopentoses ultimately detected and plausibly explain the absence of others whose recovery rates were below our detection threshold for the limited sample available for analysis. Importantly, these recovery tests provide evidence of non-uniform behavior among individual aldopentoses, with variable recoveries (Table 1) and degradation patterns (Supplementary Fig. 10) under identical conditions, suggesting sugar-dependent interactions with the sample matrix and/or during analytical processing. This highlights the need for standardized protocols employing closely resembling meteorite matrices in procedural blanks to ensure accurate blank correction when quantifying extraterrestrial abundances and enantiomeric excesses, especially for inter–parent-body comparisons.

Aqueously altered amino acid signatures in Orgueil
We simultaneously analyzed amino acids in the same sample extract to (1) monitor potential biological contamination in the absence of isotopic measurements, (2) evaluate the efficiency of our modified methodology with previous analyses of Orgueil samples, and (3) contextualize sugar abundances relative to better-characterized organic molecules within the same fragment. Given the limited availability of sugar data in the literature, amino acids—abundant and well-documented in Orgueil (Table 2)—served as a valid reference point. A total of 25 amino acids, including proteinogenic, rare, and non-biological types, were detected. The abundances of the identified amino acids are summarized in Table 2 and compared with previously reported data for Orgueil51,52. The concentrations of the most abundant amino acids, glycine and β-alanine, closely align with previous reports, reinforcing their status as characteristic amino acids in CI, CM1, and CR1 meteorites51,52. A similar agreement was observed for C3 and C4 amino acids, except for 4-ABA. However, the C5 amino acids were present at concentrations roughly ten times lower in our extract compared to those reported in previous studies. Our analysis also revealed several amino acids not previously identified in Orgueil, including four proteinogenic amino acids (threonine, proline, leucine, and isoleucine) and six rare amino acids (N-methylglycine, N-ethylglycine, 2,3-DAP, 2,4-DAB, norleucine, and allo-isoleucine).

The distribution of amino acid structural isomers in meteorites varies significantly across different groups, reflecting distinct parent body conditions and alteration histories12,49,53. Orgueil (CI1) samples display markedly lower total amino acid abundances compared to less aqueously altered CM2 (e.g., Murchison) and CR2-CR3 chondrites—a pattern attributed to extensive aqueous processing on their parent bodies54,55. This lower content is particularly pronounced for hydrophilic amino acids, likely resulting from destruction during prolonged aqueous alteration and analytical biases due to phyllosilicate-rich matrices (>90 vol.%), which trap amino acids and reduce extraction efficiencies55. The predominance of glycine and β-alanine aligns with CI chondrite alteration trends, suggesting formation via HCN polymerization and Michael addition in an ice-rich parent body containing ammonia, hydrogen cyanide, and cyanoacetylene52,53.

The enantiomeric ratios of selected chiral amino acids were calculated as L-enantiomeric excess (%eeL) (Table 3) to evaluate potential contamination during the analysis. Alanine and aspartic acid showed rather small L-excesses, while other proteinogenic amino acids (serine and valine) exhibited significant L-excess. This aligns, however, with previous data from Orgueil16,51 (Table 3) where high L-excess for serine/aspartic acid (in unhydrolyzed samples) was reported. The non-proteinogenic amino acids 2-ABA and 3-AIB were found in nearly racemic proportions. Notably, isovaline exhibited minor L-excess, matching reported values for non-hydrolyzed samples51,52.

Methods
Sample preparation
A 178.3 mg fragment of the Orgueil meteorite, of a total of 1.0 g allocated by the Muséum national d’Histoire naturelle (MNHN) in Paris and stored in a plastic container (Supplementary Fig. 1), was analyzed in this study. The fragment was transferred into a pre-weighed 5 mL V-Vial (V-Vial® Wheaton) using clean tweezers inside a Class II laminar flow safety cabinet (Thermo Scientific MSC-Advantage Class II). All glassware was cleaned with 96% ethanol and Milli-Q water, then wrapped in aluminum foil and heated at 500 °C for 5 h. Other labware, including needles, caps, spatulas, tweezers, PTFE frits (20 μm pore size, Supelco), and PTFE disposable liners (Supelco), were thoroughly cleaned with HPLC-grade ethanol and Milli-Q® water, dried with a stream of pure nitrogen, and wrapped in pre-burned aluminum foil until further use. Biopur tips (2–200 μL and 50–1000 μL Eppendorf epT.I.P.S. Biopur) were employed when needed.

Ultrasonic-assisted extraction
Ultrasonic extraction was performed using a Fisherbrand FB15049 (Elma Schmidbauer GmbH, Singen) at a fixed frequency of 37 kHz operating in sweep mode. Prior to extraction, the water bath was degassed for 1 to 5 min to remove entrapped air and dissolved gases. 3D printed holders were employed to fix the position of the vials containing the samples in a reproducible way. The temperature of the bath was maintained between 15 and 21 °C. For high-temperature extractions, an MS-100 Thermo Shaker incubator was employed. Additional instrumentation used for sample pre-treatment, including specifications and operating parameters, is detailed in the Supplementary Note 1.

The extraction protocol applied for analyzing the Orgueil sample is schematically illustrated in Supplementary Fig. 2. A procedural blank (PB), without a matrix, was prepared alongside the sample. Two distinct extracts were obtained: a methanolic (Sigma Aldrich, >99.9%) extract, expected to contain extracted sugars and minor quantities of amino acids, and an aqueous extract, primarily containing amino acids. Subsequently, multiple water (Milli‑Q Direct 8 apparatus, 18.2 MΩ cm at 25 °C, <2 ppb total organic carbon) extraction steps, including conventional hot-water extraction, were performed to enhance amino acid recovery. The detailed water extraction procedure for each step was as follows: 1. Cold methanol extraction (sugar fraction): The Orgueil fragment was crushed with 1.784 mL of methanol (MeOH) using a glass rod to ensure thorough solvent penetration. The sample was then vortex-mixed and sonicated for 10 min at 17–20 °C. After sonication, it was centrifuged at 9500 × g (9000 rpm) for 10 min with a Hettich Universal 320 centrifuge with an angle-fixed rotor model 1620A, and the supernatant was transferred to a 25 mL glass bottle. This extraction process was repeated five times, with all extracts combined into the same 25 mL flask. To minimize the co-evaporation of volatile compounds during pre-concentration under low pressure, 5 mL of water was added to the methanol extracts. The sample was then stored in the fridge at 5 °C until subsequent purification and fractionation. 2a. Cold water extraction: After methanolic extraction, the extraction continued seven more times on the matrix residue, using water instead of methanol. The resulting supernatants were transferred into a separate 25 mL glass bottle. The sample was then stored in the fridge at 5 °C until subsequent purification and fractionation. 2b. Hot water extraction: Next, 3.6 mL of water was added to the 5 mL vial containing the meteorite residue for hot-water extraction at 100 °C for 21 h. The resulting extract was then centrifuged at 9500 × g and combined with the cold-water extracts from step 2a. 2c. Cold water extraction: Three additional cold-water extractions were performed on the remaining matrix using 1.784 mL of water per extraction. The resulting supernatants were combined with the previous aqueous extracts (2a and 2b) for purification and fractionation.

Ion exchange chromatography (IEC)
Purification and fractionation. The methanolic extracts (approximately 15 mL MeOH/H2O (2:1, v/v) were loaded onto the corresponding ion exchange chromatography (IEC) columns in 200 μL portions using a Pasteur pipette (Supplementary Note 1). Eluates were collected in a 25 mL pear-shaped flask. The 25 mL bottles containing the extracts were rinsed with 5 × 0.5 mL of H2O to optimize compound recovery. The rinses were then eluted through the columns and collected in the same 25 mL pear-shaped flask. The water extracts from both cold and hot extractions (approximately 21.5 mL) were subsequently eluted through the columns in 200 μL portions without prior acidification to prevent potential racemization of the α-amino acids (Section 1.5). One milliliter of water was used to wash the walls of the columns. The resulting eluate was collected in a separate 25 mL pear-shaped flask, as it was not expected to contain sugars or amino acids, the latter of which should remain retained onto the column. Finally, to recover the amino acid fraction, 18 × 1 mL of NH3 (aq) 2 M were eluted through the column and collected in a third 25 mL pear-shaped flask.

Pre-concentration and drying. The resulting sugar and amino acid fractions from the Orgueil sample and the procedural blank without matrix were then pre-concentrated to a final volume of ~100 μL using a rotary evaporator. For this, the pressure was gradually reduced from 500 mbar to a final pressure of 25 mbar (25 °C) for the sugar fraction and 20 mbar for the amino acid fraction (26–27 °C). Each concentrated fraction was transferred to a separate 1 mL V-Vial, and the pear-shaped flasks were rinsed with 3 × 150 μL of H2O to recover any remaining analyte from the inner walls of the flasks. Finally, the samples were dried under a gentle flow of nitrogen before compound-specific derivatization. While the amino acid fraction could be dried to completion within approximately 3 h, the presence of matrix components in the sugar fraction delayed drying to up to 6 h and likely resulted in residual water remaining in the matrix (Supplementary Note 3).

Identification and quantification by enantioselective two-dimensional gas chromatography
Derivatization. The sugar fractions of the extracted samples and procedural blanks were derivatized into methylboronic acid esters following the protocol of Garcia et al.47. This involved adding 30 μL of a methylboronic acid (MBA) solution (10 mg mL–1 in pyridine) to the dried samples, vigorous vortex-mixing and heating at 60 °C for 30 min. After cooling for 10 min, the samples were then dried under a gentle stream of nitrogen, leaving approximately 2–3 μL of solvent to prevent the loss of volatile derivatives. Finally, the MBA derivatives were dissolved in 30 μL of ethyl acetate containing methyl laurate (ML) as an internal standard at a concentration of 10–6 M. Amino acids were derivatized into N-trifluoroacetyl-O-methyl (N-TFA-O-Me) esters following the protocol of Pepino et al.48. First, 120 μL of a methanol/acetyl chloride (MeOH/AcCl) solution (4:1, v/v) were added, and the mixture was vigorously stirred and heated at 110 °C for 1 h. After cooling for 10 min, the sample was dried under a gentle stream of nitrogen, leaving approximately 2 μL of solvent to prevent the loss of volatile derivatives. Next, 120 μL of a dichloromethane/trifluoroacetic acid anhydride (DCM/TFAA) solution (4:1, v/v) was added, stirred for 10 s, and heated at 100 °C for 20 min. The solution was then cooled and fully dried with nitrogen. Finally, the N-TFA-O-Me ester derivatives were dissolved in 30 μL of chloroform containing ML as an internal standard at a concentration of 10–6 M.

Analysis. The sugar and amino acid fractions from the Orgueil sample were analyzed using comprehensive two-dimensional gas chromatography coupled with reflectron time-of-flight mass spectrometry (GC×GC–TOF-MS) equipped with a dual-stage thermal jet modulator (Pegasus BT 4D, Leco Corp.). The injector and ion source temperatures were maintained at 230 °C, while the transfer line was set to 240 °C. Aliquots of 1 μL were injected in splitless mode. Hydrogen was used as carrier gas at a constant flow rate of 1.2 mL min–1. After each injection, the sample GC vial was immediately recapped and stored at 4 °C to prevent degradation of the amino acid and sugar derivatives before subsequent injections.

For sugar analysis, the GC×GC column configuration consisted of a CP-Chirasil-Dex CB primary column (27.15 m length × 0.25 mm inner diameter (ID), 0.25 μm film thickness, Agilent Technologies) coupled to a DB-WAX secondary column (1.61 m × 0.1 mm ID, 0.1 μm film thickness, Agilent Technologies). The primary oven was programmed as follows: an initial hold at 55 °C for 1 min, followed by a temperature increase of 10 °C min–1 to 90 °C, where it was held for 8 min. The temperature then increased at 2 °C min–1 to 190 °C, with a final isothermal hold at 190 °C for 15 min. The secondary oven and thermal modulator maintained constant positive temperature offsets of 30 °C and 15 °C, respectively. A modulation period of 5 s was applied. The reflectron TOF-MS operated at a 150 Hz storage rate, with a mass range of 50–500 amu and a microchannel plate detector voltage of approximately 2 kV and a solvent delay of 10 min.

For amino acid analysis, the column set-up included a Lipodex E primary column (24.95 m length × 0.25 mm inner diameter, Macherey-Nagel) coupled with a DB-WAX secondary column (1.7 m length × 0.12 mm inner diameter, 0.1 μm film thickness, Agilent). The primary oven was programmed as follows: an initial hold at 40 °C for 1 min, then heated to 80 °C at 10 °C min–1, holding for 10 min. The temperature was then increased to 120 °C at 1.3 °C min–1, followed by an increase to 152 °C at 0.8 °C min–1, and finally raised to 185 °C at 10 °C min–1, where it was held for 10 min. The secondary oven was operated with a constant positive temperature offset of 35 °C, and the thermal modulator hot jets had a temperature offset of 15 °C. The modulation period was 6 s. The reflectron TOF-MS operated at a 150 Hz storage rate, with a mass range of 40–500 amu, a microchannel plate detector voltage of approximately 2 kV, and a solvent delay of 9 min.

Analyte identification was performed by comparing retention times across both chromatographic dimensions and mass spectra (within a 500-ppm mass tolerance) with a mixed analyte standard. Quantification was performed using four-point calibration curves for the target analytes ranging from 5 × 10–8 M to 10–6 M, with manual integration conducted via LECO Corp. ChromaTOF™ software.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "Review comments on NCOMMS-25-43746\nOverall: The paper by Leyva et al. reported the detection of sugars in the samples returned from the asteroid (162173)\nRyugu, as well as that in Orgueil meteorites. The authors utilized an ultrasonic-assisted extraction and a stereoselective\nanalytical method using GCxGC-TOF-MS. As a result, they reported the detection of D and L-arabinose and D and L-xylose\nfrom the extract from Ryugu. From the Orgueil extract, the detection of not only arabinose and xylose, but also other\naldopentose sugars such as ribose, lyxose, and ribulose was reported. The present results were the second detection of\nabiotic aldopentose sugars in extraterrestrial samples after Furukawa et al. (2019), who confirmed the presence of\nindigenous sugars based on their 13C enrichments. On the other hand, enantioselective analyses of sugars were performed\nfor the first time in the present study, which can, in principle, definitely distinguish between abiotic and biotic sugars.\nThe detection of biologically relevant molecules in extraterrestrial materials is of special interest from the viewpoint of\nprebiotic evolution and the origin of life on Earth and elsewhere in the solar system. Moreover, the detection of sugars, which\nmay be minor in extraterrestrial materials, from tiny portions of Ryugu samples is challenging. So, the report on the\nsuccessful detection of sugars in such a tiny, valuable sample deserves publication in Nature Communications.\nHowever, there is a critical problem in the present manuscript: a blank control was really insufficient in the present study. For\nexample, although significant sugar contaminants were detected in the procedural blank (PB) experiment, the authors did\nnot evaluate their contribution to the detected sugars in Ryugu and Orgueil. This is based on their opinion that the recovery\nof sugars is poor when some mineral matrices are used. If no sugars were detected in the PB without such minerals, the\nsugars detected in the sample are reasonably acceptable as indigenous to the samples. However, as long as\nsignificant contaminations are present in the PB and no evaluation of their contributions is performed, the reported quantification values\nand the enantiomeric parameters cannot be accepted as indigenous to Ryugu and Orgueil.\nI guess pristine Ryugu samples are no longer available, so the reanalysis of Ryugu samples would be difficult, unfortunately.\nHowever, according to the authors, they still have enough Orgueil meteorite samples. So, I strongly recommend authors to\nevaluate the potential contamination very carefully under the same analytical conditions with the meteorite samples and to\nperform extraction and analysis of sugars in Orgueil meteorites again. As for the Ryugu results, based on the new analyses\nof PB and Orgueil, the presence of sugars should be evaluated in more detail, although any reliable quantification would not\nbe possible. I hope the following comments are helpful in improving the current manuscript.\n-L8: I cannot understand the meaning of “unequal distribution”. This should be rephrased appropriately.\n-L10, “robust formation of sugars in laboratory simulations of interstellar ice chemistry”: I do not think that the robust formation\nof sugars in interstellar ices has been established in earlier laboratory experiments. For example, de Marcellus et al. (2015)\nand Meinert et al. (2016) performed laboratory experiments at liquid-nitrogen temperature, which may be less relevant to\nprocesses in the coldest regions in the interstellar medium (ISM), whose typical temperature is as low as 10 K. Nuevo et al.\n(2018) and Zhang et al. (2024) used unrealistic ices in the ISM for the reactants (e.g., methanol and CO mixed ices, water\nand methanol mixed ices, without other components). I do not doubt the formation of sugars in their experiments, but I do not\nfully agree with the “robust formation of sugars” in interstellar ice chemistry.\n-L13, L82-85: “ultrasonic-assisted extraction” is not a new technique for the extraction of sugars from meteorites. The\nenantioselective analyses by GCxGC should be emphasized more.\n-L36: Ref 13 (Yokoyama et al.) did not report the presence of amino acids and nucleobases in Ryugu.\n-L40-42: What is the meaning of “a significant gap”? It does not make sense if the authors expect the possible formation of\nsugars in laboratory experiments under the simulated ISM or parent body conditions. As pointed out above, laboratory\nexperiments did not necessarily simulate the actual conditions in extraterrestrial environments. Moreover, not only the\nformation of sugars (refs. 16-22) but also their degradation event should have taken place in each environment. Without\nconsidering both effects, the expression “significant gap” is too strong.\nL56-60: “This concern ... sample processing.” These sentences should be deleted because they would give a negative\nimpression to readers, as if all returned samples have been contaminated. Even without these sentences, it makes sense to\nreaders.\nL71-73: As for arabinose in NWA 801, Furukawa et al. (2019) did not report the d13C value due to the significant\ncontribution by the co-eluting peak. However, they also claimed that arabinose and ribose in Murchison and ribose in NWA\n801 are not significantly affected by their co-eluting peaks. It seems to me that the sentence here is based on the current\nauthor’s subjective opinions only. Hence, the sentence in Lines 71-73 should be deleted.\nL87: This should be deleted since this is a repetitive sentence of L80-82.\nL90-92: This sentence is too strong since it is just based on the author’s assumption.\nL103: Which previous studies do the authors point out? Cite some references here.\nL119: “MBA” is appropriate as an abbreviation of methyl boronate?\nL124, “significantly above the procedural blank levels”: This sentence is overstated.\nL128, “near-racemic ratio (D/L ~ 1.0)”: This sentence is also overstated since no blank control has been done.\nFigure 2: In the PB data, not only L-Ara but also D-Ara (~34.10 for 1D, =1.8 for 2D) should be present, although the peak\nintensities vary significantly between D and L enantiomers, possibly due to the biological contamination of L-Ara and the\ncontamination from the standard reagent of D-Ara (if the authors use the “expansion” technique as used in Figure 6a, this\npeak should be observed more clearly). The presence of D-Ara in PB should be evaluated in more detail. Since the range of\nthe color bar for PB (60154-300000) is significantly different from that for the Ryugu (11835-41561), the D-Ara abundance in\nPB may be significantly underestimated. Based on the color bar, the abundance of D-Ara in PB may be ~100,000 or\nsomething like that. Assuming the recovery of 30% for Ara (Line 150), the possible abundance of D-Ara contributed to the\nRyugu data is ~30,000, which is comparable to that of D-Ara in the Ryugu data. Also, as for L-Ara, the abundance in the PB\n(300,000) may be able to explain the abundance in Ryugu, assuming again that the recovery is ~30%.\nFigure 3: Since the peak height for D-Xyl in PB looks much higher than that in Ryugu, the authors should evaluate the\npossible contribution from the contamination to the sample peak. Also, L-Xyl should be present in PB, although its\ncontribution seems less dominant compared to D-Ara in PB (Figure 2B). The detection of L-Xyl, as well as that of D-Ara, in\nPB strongly suggests that there are multiple contamination sources, such as terrestrial biology and standard reagents in the\npresent study. Without such evaluation, it is hard to accept the author's statement that sugars are detected in the Ryugu\nextract.\nFigure 4: Why are Ara and Xyl, whose detections in PB are shown in Figure 5, not observed in the PB data? Also, the\ndetection of L-ribose and L-xylose in PB indicates the incorporation of their standard reagents.\nFigure 5: D-Ara should be present in the PB, although not indicated in the chromatogram. The peak intensity of D-Ara in the\nPB is ~100,000 or so. Assuming the recovery of 30% for Ara, the contribution of the contamination to the Orgueil data seems\nvery high.\nFigure 6: The presence of L-Xyl is highlighted in an insert, which can visualize the small peak for L-Xyl. This technique\nshould be applied to the PB data; D-Ara in Figure 2, L-Xyl in Figure 3, D-Ara in Figure 5, and L-Xyl in Figure 6. The color in\nthe insert does not seem to correspond to the color bar. Please modify it. Also, “Orgeuil” in the title is a typo.\nL196: “same parent body” -> “same fragment”.\nL199: sumarized -> summarized\nL197-208, amino acids in Ryugu: Some examples of the raw data (chromatograms of samples and blank, for example) for\nthe detection of amino acids should be presented somewhere in the article. How much is the recovery of major amino acids?\nDiscussion: Many sentences overlap with those in the Introduction. The first two paragraphs are mostly a summary of\nprevious studies.\nL250: As pointed out earlier, the ultrasonic-assisted extraction and ion-exchange chromatography have already been\napplied in Furukawa et al. (2019). Please focus on the advantages of using GCxGC.\nL264: The proposed near-racemic nature of arabinose is not guaranteed due to the lack of any contamination control.\nL266, “only biological enantiomers of both sugars were detected”: This contradicts the PD data as indicated above.\nL273-274: “D-xylose/arabinose” may be “D-xylose/L-arabinose”. This sentence seems to contradict the author’s claim that\n“The near-racemic proportions observed in several of the detected sugars support their abiotic and potentially extraterrestrial\norigin” in L85-87.\nL278: I’m confused. The authors presented the concentration of sugars in Ryugu in Table 1. However, this is an appropriate\nconclusion.\nL285-286: Why can the presence of C6 sugars not be excluded?\nL293: NH3 in Ryugu is much less than Orgueil. Ref 59 did not mention it. Yoshimura et al. (2023) Nature Communications,\n14, 5284, reported the low concentration of NH3 in Ryugu. Please refer to Ref 14 which compares the concentration of NH3\nin various samples.\nL296-314: Without blank corrections, the discussion in these paragraphs does not make sense at all.\nTable 1: Show the blank-corrected values for sugars in Ryugu and Orgueil. Also, footnote d should be deleted since d13C is\nnot relevant to the data in this table. This statement is merely an attempt to downgrade prior studies.\nTable 2: In the column of A0106, the superscript “a” may be wrong. Also, how did the authors perform blank correction? Are\nthe sample data corrected using that for PB without minerals? Please clarify. If so, such a blank correction is not appropriate\nbecause the same analytical procedures are not applied to both samples and PB. Show the blank-corrected values for\namino acids in Orgueil, too. Or, show only blank-corrected values for both Ryugu and Orgueil. Negative values after the\nsubtraction of PB should be an indicator for the incorporation of many contaminants during analytical procedures. How do\nthe authors explain this?\nTable 3: Enantiomeric compositions should be calculated by their brank-corrected concentrations.\nSupplementary Information\nL129-, Ion exchange chromatography: It seems that the cold and hot water extracts are not acidified before IEC, which\nresults in the zwitterionic forms of amino acids in the extract. The authors mentioned that they adapted a protocol from\nSimkus et al. However, the author’s protocol is different from that shown in Simkus et al. and Amelung and Zhang (2001)\nwhich Simkus et al. referred to in their paper, in the use of ethanol and methanol in the pretreatment. Also, the use of\nH2O/MeOH for the wash of the column walls is different from these earlier papers. It seems to me that the use of methanol\nand ethanol for the treatment for cation-exchange chromatography is not so common. Were sugars and amino acids\nrecovered well in this protocol? How much are their recoveries in this protocol only? Please clarify them.\nL217: Why sugars in Orgueil were analyzed in a way different from that applied to Ryugu extracts?\nL234-235: In the footnote of Table 1, the authors mentioned that the quantification values are uncorrected for procedural\nblanks. While, the description in these lines seems to contradict the description in Table 1. Please clarify.\nL237, Supplementary Note 2: Regardless of the degree of recovery, there is no doubt that there are significant sugar\ncontaminations incorporated into the sample during analytical procedures. What is (are) the source(s) of such significant\ncontamination? Without evaluating contamination, the reported concentrations of sugars and amino acids, as well as their\nee, cannot be accepted as the native values for Ryugu and Orgueil samples.", "reviewer_2": "Major comments:\nThis research investigated sugars in the sample of the carbonaceous asteroid Ryugu. The sample is extremely valuable,\nand the chiral separation of sugars represents a significant novel development. Thus, this research is suitable for\nconsideration in Nature Communications. However, I have several concerns with this analysis, primarily related to the\npotential contamination of biological and unclear sources of sugars, which may be derived from a standard chemical\nmixture. Suppose this contamination occurred outside of the sample solution, such as in the GC-MS injector. In that case, a\nrepeat analysis of the sample with a clean GC-MS system will provide a convincing result. However, if this contamination\noccurred in the sample solution, I have no idea how to show the presence of extraterrestrial sugars in the Ryugu with this\nsample. Thus, the manuscript, at least in this form, is not sufficient to show that the Ryugu sample contains abiotic sugars.\n1. The central issue is the contamination of both D-sugars and L-sugars in the sample of Orgueil and potentially Ryugu. In\nthis type of analysis, the procedural blank that undergoes the same conditions as the sample is crucial for demonstrating\ncontamination. The procedural blank of Orgueil shows contamination of D-ribose, L-ribose, D-lyxose, and L-lyxose. Since L-\nribose and L-lyxose are not biological contaminants, this suggests that cross-contamination of the standard or sample\noccurred with the procedural blank. I guess the contamination was from the standard because the significantly higher\nabundance of ribose and lyxose than arabinose and xylose is not reasonable as abiotic sugars, and the relative abundance\nbetween sugars is different from that of the Orgueil. Given the presence of cross-contamination, the chromatogram of the\nOrgueil sample may be consistent with the sugar composition of the standard + biological contaminants. The author should\nexplain considering this possibility, both in Ryugu and Orgueil. To discuss this possibility, the authors should show the\nchromatogram of the standard mixture.\n2. The amounts of D-xylose and L-arabinose in the procedural blank for the Ryugu sample should be listed in the Table. The\nabundance of D-xylose in Ryugu maybe comparable to that detected in the procedural blank. They should be compared.\n3. L268-269 and table 1: The authors describe that “Among these, ribose, lyxose, and ribulose showed racemic distributions,\nconsistent with an extraterrestrial origin.” However, near-racemic ribose and lyxose are also detected in the procedural\nblank, indicating that the detected ribose and lyxose are possible contaminants from the standard. If we suppose that the\namounts of D-arabinose and L-xylose are authigenic of Orgueil, why do ribose and lyxose (rare sugar) have 20-30 times\ngreater amounts? As the author shows, the recovery of ribose is only 4%, indicating that ribose is present at a concentration\nmore than 300 times that of arabinose. This is not reasonable. The compositions of sugars in the procedural blank implies\nthat the same source of contamination occurred more significantly to Orgueil.\n4. The data on ribulose is missing. This should be shown.\n5. The chromatograms and abundance of ribose and lyxose in Ryugu should be shown.\n6. The authors underlined the novelty and advantage of this extraction repeatedly. However, the ultrasonic-assisted room\ntemperature extraction has been conducted in previous studies with water and 2% HCl (Cooper et al. 2001 and Furukawa et\nal., 2019). The clear difference in this study is extraction by methanol. However, extraction of sugars with methanol is not\neffective, owing to their low solubility compared to water and HCl. For example, Alessandro et al., (Alessandro C. Galvão,\nMaicon R. Zangalli, Pedro Felipe Arce, Weber S. Robazza, Solubility of fructose and sucrose in mixtures of methanol and\nwater: Experiment and application of equations of state and activity coefficient model, Journal of Food Engineering, 369,\n2024,) shows that the solubility of fructose in methanol is less than 10% in water. The loss of the extraction is evaluated in\nthis method using the addition of sugars to Orgueil. Thus, this is not an essential problem, but clearly this extraction is not the\nadvantage but disadvantage from previous studies.\n7. The table 2 shows the abundance of amino acids and their blank-subtracted values. The values of “UNH(a)” represent\nsample + contaminants and the value with “UNH(b)” are real extraterrestrial amino acids. Many of the values in “b” is n.v.,\nmeaning that they are smaller than the blank. This means that the procedural blank does not work as procedural blank.\n8. The manuscript should show reproducibility of amino acid analysis. If they consider the reproducibility, several values in\nthe “b” column may be not reliable. For example, D-Ala was detected in the sample and blank at 0.326 and 0.378,\nrespectively. If the reproducibility is 10%, the difference is not clear. This may happen also for 2-ABA.\n9. The amounts of amino acids in the procedural blank for Orgueil should be shown in the table.\n10. Any meteorite has the potential for contamination from sampling to curation. To prevent this effect in previous studies of\nsugars, meteorites were trimmed to remove potentially contaminated surfaces (Cooper et al. 2001 and Furukawa et al.,\n2019). Did the authors trim Orgueil to remove contamination, or did the authors use an inner part of the original fragment of\nOrgueil? The data of Orgueil analysis in this manuscript shows contamination of biological sugars and amino acids. If they\nanalyzed with exposed surface, this could be the primary reason of biological contamination.\nSpecific comments:\nAbstract: The present data set shown in the manuscript does not sufficiently represent the presence of extraterrestrial sugars.\nThe color code for the sample and procedural blank should be within the same range, from 0 to the maximum, to allow\nreaders to compare them. For example, Fig 1 A and B should be from 0 (blue) to 300000 (red).\nThe total 2D chromatograms covering all investigated sugars for samples, blanks, and the standard should be shown. The\npresent manuscript contains only Orgueil and its procedural blank (Fig. 4).\nL57: Even though there is some potential for the microbial colonization of Ryugu sample, the evidence is poor in this cited\npaper limited in shape, which can be formed by withering. Also, this potential contamination happened in the allocated\nsample by the researchers which means that the allocated sample was not contaminated. The present explanation is\nconfusing.\nL102-103: The author explained here that “Key to this methodology is a mild extraction protocol that replaces conventional\nhigh-temperature acid hydrolysis with milder ultrasonic-assisted extraction to prevent thermal degradation of sugars.”\nHowever, this is not correct. The previous sugar extraction was conducted at room temperature with water (Cooper et al.,\n2001) or 2% HCl, which is lower concentration than amino acid hydrolysis (Furukawa et al., 2019) with sonication. Thus,\nultrasonic-assisted mild extraction is not new.\nL123: The manuscript describes that “we unambiguously detected both enantiomers of arabinose and xylose in Ryugu\nextracts at concentrations significantly above the procedural blank level.” However, the amounts of arabinose and xylose in\nthe procedural blank are not shown in the manuscript. Figures 2 and 3 clearly show that there are larger amounts of L-\narabinose and D-xylose in the procedural blank than in the Ryugu sample. So, the description in the manuscript is not\ncorrect. The 3D peaks of D-arabinose and L-xylose look larger in Ryugu than the procedural blank, but these peaks in\nRyugu are magnified in these figures. So, the figure does not provide information on their amounts.\nIn the revised manuscript, the amounts of both D and L arabinose and xylose in the procedural blank should be shown in\nTable 1 and explained based on these amounts.\nL128: The manuscript explains that arabinose in Ryugu has a D/L approximately 1.0. However, Table 1 shows that the D/L\nof arabinose in Ryugu is 0.727. They are not racemic, but D-rich.\nTable 1: The manuscript explains in L 142 that “D-arabinose and L-xylose as ~0.01 nmol/g and ~0.001 nmol/g, respectively”.\nThese values would not be consistent with the data in Table.\nL145-146: The manuscript discusses that the lower abundance of contaminants in Ryugu than PB was caused by the\nadsorption by minerals. In this case, what was the source of the contamination? Did the authors analyze solvents every time\nbefore the analysis of the sample and PB? If so, please describe this to eliminate the possibility of cross-contamination in\nGC-MS. Otherwise, the cross-contamination may explain the chromatogram of Ryugu (real Ryugu+PB) or (PB+standard).\nThe PB of Orgueil shown in Fig. 4 shows that D- and L-lyxose and D- and L-ribose are contaminated. D- and L-lyxose are\nrare sugars and L-ribose is non-biological sugar. Thus, they could not be biological contaminations. So, they could be\ncontaminated from the standard chemical mixture in the GC-MS. If this happened in the Ryugu sample. The presence of L-\nxylose and D-arabinose could be explained by this effect. The authors should show the analytical blank before the Ryugu\nanalysis.\nL167: The chromatograms of ribulose should be shown in the manuscript.\nL167: The author should show chromatograms of Orgueil, procedural blank, and the standard of ribulose.\nL172-175: The author discussed that acid extraction of sugars from Murchison reported in Furukawa et al. (2019) may\nintroduce sugar contamination and promote sugar formation reaction. However, in the previous study, the paper described\nno detectable pentose contamination in the procedural blank. Thus, the contamination from 2% HCl in the extraction is\nunfounded.\nFurther, sugar formation by the formose reaction is highly sensitive to high pH, indicating that low pH is more suitable for\nextraction. The higher stabilities of sugars at lower pH are also evident in other previous study, in which the\ndegradation of ribose is 100 times lower at pH4.5 compared to 6.5 (Larralde et al., 1995).\nThus, this discussion should be removed.\nL244-245: Arabinose in Ryugu is enriched in L-form.\nL293: The author discussed that abundant ammonia stabilized sugars, by maintaining pH for optimal aldol condensation.\nHowever, this is not correct. Ammonia react with sugars to form may by-products (e.g., Kebukawa et al., Science Advances\n2017). Further, aldol condensation promoted by high pH consume sugars as shown in many previous studies including the\nauthor’s work (Vinogradoff et al., 2024).\nFigure 2-6: Do the 2D and 3D chromatograms show total ion chromatograms or selected ion chromatograms? This should\nbe explained in the caption with m/z range or m/z values.\nFigure 4 and 5: The assignment of D-arabinose is different between Figure 4 and 5.\nMinor comments:\nL28: Proteins are better described as catalytic biopolymers rather than informational biopolymers, since the term\ninformational biopolymers is widely used to express the biopolymers that have gene information.\nL80-97: These paragraphs mostly describe results and implications. Thus, they should be merged in the\nfollowing section.\nL82: ribuloses to ribulose\nL98: The title of this section should be “Results and Discussion”\nL118: “as well as the the C5 ketose” to “as well as the C5 ketose”\nL155: (PB) to (B)", "reviewer_3": "Below you will find my review of manuscript NCOMMS-25-43746 entitled “Abiotic sugars in 9162173) Ryugu and the\nprimitive CI carbonaceous chondrite Orgueil” and submitted to Nature Communications.\nOverall this manuscript is very interesting. The results presented are important to the astrobiology and planetary science\ncommunities, and timely given the ongoing studies and publications related to the analyses of samples from asteroids\nRyugu and Bennu. There are, however, a few things about that manuscript that bother me, and I would like the authors to\nconsider my comments below before I can recommend this manuscript for publication in Nature Communications.\nGeneral comments:\nThe thing that bothers me the most about this manuscript is the strange imbalance between the study of sugars and that of\namino acids. On the one hand, the title of manuscript only refers to the detection of sugars in Ryugu and Orgueil samples,\nbut on the other hand, half of the paper is dedicated to the detection of amino acids. Indeed, the Results, Discussion, and\nMethods section all significantly describe the protocol, detection, and data interpretation of amino acids in those samples at\nalmost the same level as for sugars. In particular, Tables 2 and 3 are huge and only related to amino acids. But somehow\nthe title doesn’t mention anything about amino acids at all.\nI do acknowledge and appreciate the fact that the authors included detailed protocol and results obtained for the detection of\namino acids in both Ryugu and Orgueil samples, and I understand that this information helps (1) compare the results\npresented in this manuscript with previous studies, and (2) assess the origin and level of contamination of the samples for\nboth amino acids and sugars, i.e., extraterrestrial vs. terrestrial contamination.\nHowever, this makes the actual objective of this manuscript confusing, to say the least. Is the manuscript about the detection\nof sugars (as the title suggests) or about the detection of both sugars and amino acids? Was this manuscript originally two\nseparate manuscripts that eventually ended up stitched together, because some information from the study of amino acids\ncould help support the extraterrestrial origin of sugars?\nIn addition, there are two statements in the manuscript that are not supported by any of the figures nor the tables:\nClaim 1: The manuscript clearly mentions several times the (first reported) detection of ribulose in both Ryugu and Orgueil\nsamples. However, there are no figures to support this claim anywhere. At the very least, this claim should be supported by a\nfigure with GCxGC-TOFMS data (chromatograms + mass spectra) showing the detection of ribulose and a comparison with\nthe procedural blank and the reference standard, similarly to other detected sugars. As is, the authors are asking the readers\nto accept the first detection of ribulose in extraterrestrial samples on a “trust me when we tell you” basis.\nClaim 2: Similarly, there are no supporting figures for the detections of the amino acids mentioned in the manuscript. I\nunderstand that the current version of the manuscript wants to focus on the detection of sugars (see my other general\ncomments above), but at the same time the authors make many claims regarding the detection of several amino acids, use\nthose data to determine enantiomeric excesses and to show that the amino acid data support an extraterrestrial origin for\nboth the sugars and amino acids detected here. Therefore, supporting the claims of detection of amino acids is critical to the\nmessage this manuscript wants to convey and, like the detection of ribulose, these detections can’t be based only on good\nfaith.\nFinally, I am a bit concerned about the levels of contamination in the procedural blanks (PBs). Indeed, Figures 2, 3, and 5\nshow high levels of contamination for the compounds (both sugars and amino acids) that the authors are searching for in the\nsamples. For example, the intensity of the peak for L-Ara in the PB shown in Figure 2 is over 7 times higher than the intensity\nof the peak for L-Ara in the Ryugu sample. Similarly, the intensity of the peak for D-Xyl in the PB shown in Figure 2 is\ncomparable to the intensity of the peak for D-Xyl in the Ryugu sample. I understand that other elements of the analysis still\npoint towards an extraterrestrial origin of these compounds, but this is quite concerning, and the authors should provide a\nmore solid explanation of why these abundant contaminants are still consistent with an extraterrestrial origin for these\nsugars. On a similar topic, why were the values reported in Tables 1, 2, and 3 for the abundances of sugars and amino acids\nin both Ryugu and Orgueil not corrected for PBs? How can the abundances and enantiomeric excesses found for the\ndetected compounds be compared with previous studies if the values used for these determinations are not\ncorrected?\nIn summary, some decisions need to be made by the authors regarding the revisions to this manuscript. I see 2 possible\noptions:\nOption 1: The authors could almost entirely remove the text and parts of the figures regarding the study of amino acids, and\npublish those very interesting results in a separate paper. In this case, they could easily add the GCxGC-TOFMS data\nmissing to support the detection of ribulose, expand the discussion regarding the contaminants seen in the PBs, and decide\nwhat to do with the uncorrected values reported in Table 1.\nOption 2: The authors could officially make this manuscript a study of the detection of both sugars and amino acids in Ryugu\nand Orgueil. To this purpose, they would need to add figures showing GCxGC-TOFMS data for amino acids to support their\ndetection claims, expand the discussion regarding the contaminants seen in the PBs, and decide what to do with the\nuncorrected values reported in Tables 1, 2, and 3. This option may however result in a significant increase of the length of\nthe manuscript.\nOther more specific, minor comments:\nTitle: As mentioned in my general comments, the fact that the title only mentions the detection of sugars while a lot of the text\nand the tables provided in the manuscript are about the detection of amino acids and their enantiomeric excesses is strange.\nIn the case the authors choose to fully add all the information regarding the analysis of amino acids in the manuscript,\nincluding the actual GCxGC-TOFMS data, then the title should be modified accordingly.\nTitle: Another small detail that bothers me in the title is the specific mention of “primitive” to qualify the Orgueil meteorite.\nThis is a bit in contradiction with what is mentioned in the manuscript, when it is said that meteorites that are collected on\nthe Earth’s surface, such as Orgueil, are more prone to contamination because they have been in contact with potential\ncontaminants. In that sense, even if the original piece of rock that fell from the sky, and was later named “Orgueil meteorite”,\noriginated from a primitive parent body (probably an asteroid), it is strange to specify that Orgueil is a primitive meteorite,\nwhile the samples collected from Ryugu are probably more primitive than any meteorite collected on Earth.\nLines 33–34: I often see a phrase in the introductions of papers stating that exogeneous organic materials are probably\ndelivered by extraterrestrial objects such as meteorites and interplanetary dust particles (IDPs). Is there any actual published\nstudy that shows the detection of extraterrestrial organic compounds such as amino acids and sugars in IDPs?\nLine 36: The “the” before “asteroids” is unnecessary.\nLines 44–45: I don’t understand how the RNA world hypothesis has anything to do with the critical goal to investigate the\nformation of sugars. Even if the RNA world hypothesis turns out to be wrong, the fact that sugars are used in RNA and DNA\nin all modern biological systems is the main motivation for studying the origin and formation of sugars from an astrobiological\npoint of view, no matter an actual RNA world played a role in the history of biological evolution or not.\nLines 50–52: This sentence has a negative connotation, as if only the detection of sugars in extraterrestrial materials\nmattered. Is the presence or detection of sugar alcohols and/or sugar acids in extraterrestrial materials really a bad thing?\nEven if sugars are converted into their alcohol and/or acid derivatives, their presence is also interesting, because they may\nprovide important information about the conditions (temperature, pH, precursors, etc.) under which sugar derivatives in\ngeneral were formed in the parent bodies, and because they can still be converted back to sugars under conditions that may\nhave existed on the surface or in the oceans of the early Earth.\nLine 57: Add “to” after “prior”: “prior to analysis”.\nLine 59: Add “JAXA” before “Hayabusa2” and “NASA” before “OSIRIS-REx”.\nLine 64: The reference numbers after “O” look confusing because they come right after “13C” and “15N”. Moreover, although\nthe isotopes of interest for carbon and nitrogen are specified (13C and 15N), those for oxygen are missing (18O?). In any\ncase, in particular if the isotopic number is added to O, the references should be provided in a less confusing format, e.g.,\n“(refs. 36–38)”.\nLine 122: It should be spelled “extraterrestrial” (no hyphen).\nLine 124: Figures 2 and 3 don’t display any “resolutions”, but they do display “chromatograms” or more precisely “2D-chromatograms”.\nCaptions of Figures 2, 3, 5, and 6: It is obvious that “RS” in the bottom 2D-chromatograms stands for “reference standard”,\nbut it is not explicitly defined anywhere, in contrast to “PB” for “procedural blank”, which is explicitly defined.\nLine 166: I defy anybody to be able to use the data used in Figure 4 to conclude that lyxose is detected in nearly racemic\nconditions. It’s impossible to see that from the information provided in Figure 4.\nLine 214: N-methylglycine is indeed used in biological systems, but it’s not a proteinogenic amino acid.\nLine 215: Per IUPAC convention, the “allo” in “allo-isoleucine” should be in italics.\nLine 220: The comma after “content” is unnecessary.\nLines 250–252: These sentences are a near word-for-word repetition of text provided earlier and don’t belong to the\nDiscussion section.\nLine 256: Re-order the words as: “CI (Ivuna-like) chondrites”.\nLine 260: “solar system” should be capitalized: “Solar System”.\nLines 292–294: I disagree with point (3). Too much NH3 in the system would result in higher amounts of N atoms\nincorporated into organic compounds, which would inhibit the formation of sugars and sugar derivatives and favor the\nformation of N-bearing compounds instead.\nLine 324: I believe there’s a typo and it should be “Class II” (no space).\nLine 338: I would add a hyphen between “pre” and “treatment”: “pre-treatment”.\nLines 352, 355, and 358: Those steps all mention water extractions, but no information is provided regarding the origin and\npurity of water. I know that this information is provided in detail in the Supplementary Information, but I still think it should be\nmentioned here at least once that the water used is water filtered to a purity of 18.2 MΩ cm.\nLine 374: I believe that Nature Communications follows British English spelling, and therefore the correct spelling should be\n“millilitre”.\nLine 398: From the context, I can guess that “MBA” refers to “methylboronic acid”, as it should have been defined on line\n396.\nLine 399: Inversely, the abbreviation “ML” for “methyl laurate” is defined here but never used again afterwards, even though\n“methyl laurate” is mentioned again on line 407, where the abbreviation could have been used but wasn’t.\nTable 1: No matter how loosely I interpret the numbers reported in the table, I can’t seem to find a value of 95.3% for the eeD\nof xylose in Orgueil from the abundances provided for L- and D-xylose (0.22 and 3.22, respectively). For example, if I\nassume that 0.22 and 3.22 were rounded from 0.215 and 3.224 (extreme numbers that would still be rounded up to those\nprovided in the table), the resulting eeD is 86.7%, which is still well under the 95.3% value reported in the table. Therefore, I\ndon’t understand where these 95.3% come from."}, "author_response": "Response: Thank you for your overall positive and encouraging evaluation of our manuscript, as well\nas for your insightful remarks, which have clearly helped us to refine and strengthen the work. We\nfully acknowledge the challenges in unequivocally confirming the presence of extraterrestrial sugars\nin such samples—particularly in the case of Ryugu, where the quantities available are extremely\nlimited. We have now included in the manuscript a thorough study targeting the identification of the\nsources of sugar contamination in our analyses. Distinct enantiomeric composition of arabinose in the\nRyugu fragments compared to our procedural blanks strongly supports different origin of at least some\nof arabinose detected in the Ryugu sample. Furthermore, the near-racemic ratios of some of the\namino acids found in the Ryugu fragments can be taken as a precedent for the extraterrestrial origin\nof at least some of the arabinose detected in the Ryugu extracts. In the case of xylose, the results\nremain more elusive, which we now clearly state in the manuscript. Since our spiking experiments\nclearly demonstrate the negative impact of the meteorite matrix on sugar recovery, and given that\nthe SiO₂ used in our procedural blanks does not adequately replicate the complex nature of the Ryugu\nor Orgueil matrices, we chose not to apply blank corrections to the absolute quantities or\nenantiomeric excess values of sugars detected in the extraterrestrial samples, as such corrections\ncould bias the results in an unknown manner. Rather than applying corrections, we present the\nabsolute values of sugar contents in the Ryugu and Orgueil samples, with the caution that our\ndiscussion should be considered when interpreting these preliminary quantitative data.\nFor better comparison with the existing literature on amino acids in Ryugu and Orgueil, we followed\ncommon practice and report now both the ‘absolute’ and procedural blank–corrected quantities\n(Table 1). However, we strongly caution that these absolute values should be interpreted carefully,\ngiven the current limitations of the procedural blanks typically employed in the research community.\nDetailed studies of the impact of the meteorite matrix, that are beyond the scope of the present\nmanuscript, are necessary to develop standardized protocols for blank-corrections in the future. These\nshould be then employed throughout all studies in the community to facilitate quantitative\ncomparisons between organics contained in distinct parent bodies. We expand on the above-\nmentioned points in more detail in the point-by-point responses below.\nRevised in the manuscript: Table 1: blank-corrected quantities for amino acids in Ryugu and Orgueil.\n-L8: I cannot understand the meaning of “unequal distribution”. This should be rephrased\nappropriately.\nResponse: We thank the reviewer for pointing out the ambiguity in our use of the term “unequal\ndistribution.” To improve clarity, we have revised the sentence to more accurately reflect the\nobserved variability in detection and abundance of different compound classes.\nThe revised sentence in the manuscript now reads: “The uneven detection of prebiotic organic\ncompounds in meteorites—where amino acids and nucleobases are frequently identified, while sugars\nare rarely detected and remain poorly characterized.“\n-L10, “robust formation of sugars in laboratory simulations of interstellar ice chemistry”: I do not think\nthat the robust formation of sugars in interstellar ices has been established in earlier laboratory\nexperiments. For example, de Marcellus et al. (2015) and Meinert et al. (2016) performed laboratory\nexperiments at liquid-nitrogen temperature, which may be less relevant to processes in the coldest\nregions in the interstellar medium (ISM), whose typical temperature is as low as 10 K. Nuevo et al.\n(2018) and Zhang et al. (2024) used unrealistic ices in the ISM for the reactants (e.g., methanol and CO\nmixed ices, water and methanol mixed ices, without other components). I do not doubt the formation\nof sugars in their experiments, but I do not fully agree with the “robust formation of sugars” in\ninterstellar ice chemistry.\nResponse: We thank the reviewer for this valuable clarification. We agree that the term “robust” may\nhave overstated the level of certainty and realism in laboratory simulations of interstellar ice\nchemistry, particularly in light of the limitations in temperature and ice composition highlighted in this\ncomment. In response, we have revised the sentence to more accurately reflect the current state of\nknowledge and experimental limitations while still acknowledging the relevance of experimental work\nin exploring plausible synthetic pathways. Moreover, we have included the information on previous\ndetections of glycolaldehyde, the simplest sugar, in the interstellar medium as well as on comet\n67P/Churyumov Gerasimenko.\nThe revised text in the manuscript now reads: “This disparity is particularly striking given that the\nsimplest sugar, glycolaldehyde, has been detected both in the interstellar medium and on comet\n67P/Churyumov Gerasimenko, while laboratory simulations of interstellar ice chemistry have\ndemonstrated the formation of more complex sugars, supporting their plausible synthesis under\nspace-like conditions.”\nAn additional sentence on extraterrestrial detections of glycolaldehyde was also added to the\nIntroduction section:\nRevised in the manuscript: “Moreover, glycoladehyde, a two-carbon sugar and potential precursor of\nlarger carbohydrates, has been previously detected in the interstellar medium towards the Galactic\ncenter source Sagittarius B2(N) (https://iopscience.iop.org/article/10.1086/312881) as well as on\ncomet 67P/Churyumov Gerasimenko (https://www.science.org/doi/10.1126/science.aab0689).”\n-L13, L82-85: “ultrasonic-assisted extraction” is not a new technique for the extraction of sugars from\nmeteorites. The enantioselective analyses by GCxGC should be emphasized more. –\nResponse: We thank the reviewer for this helpful clarification. We agree that ultrasonic-assisted\nextraction is not a novel technique per se and has been used for extraterrestrial sample extraction.\nWe have revised the manuscript accordingly to avoid any misleading implication.\nRevised Line 13 (Abstract): We have removed the word “novel” and now highlight instead that this\nwork presents “the first simultaneous enantioselective analysis of sugars and amino acids” in\nextraterrestrial material, which we believe better reflects the originality and significance of the\napproach.\nRevised Lines 82–85 (Main Text): We have revised the description of our method by replacing “novel”\nwith a more accurate statement: “Our analysis combined ultrasound-assisted extraction and ion-\nexchange chromatography for fractionation and purification with…”\nThis change shifts the emphasis away from the novelty of individual techniques toward the value of\ntheir integration, especially in combination with enantioselective GC×GC–TOF-MS analysis, which we\nagree deserves to be more prominently emphasized.\n-L36: Ref 13 (Yokoyama et al.) did not report the presence of amino acids and nucleobases in Ryugu.\nResponse: Thank you for pointing this out. To address this issue, we have removed the erroneous\nreference and instead cited Oba et al. (2023, Nat. Commun. 14, 1292), which provides direct evidence\nof uracil and other nitrogen heterocyclic molecules in Ryugu samples.\n-L40-42: What is the meaning of “a significant gap”? It does not make sense if the authors expect the\npossible formation of sugars in laboratory experiments under the simulated ISM or parent body\nconditions. As pointed out above, laboratory experiments did not necessarily simulate the actual\nconditions in extraterrestrial environments. Moreover, not only the formation of sugars (refs. 16-22)\nbut also their degradation event should have taken place in each environment. Without considering\nboth effects, the expression “significant gap” is too strong.\nResponse: We thank the reviewer for this thoughtful and important comment. We agree that the\nphrase “a significant gap” may have overstated the current state of knowledge, particularly given the\ncomplex interplay between sugar formation and degradation under extraterrestrial conditions—both\nof which remain challenging to replicate or fully capture in laboratory simulations. We also\nacknowledge that laboratory experiments, while informative, do not comprehensively simulate all\nconditions present in space or on meteorite parent bodies.\nTo address this, we have revised the sentence in the manuscript to better reflect the limitations and\nuncertainties involved.\nRevised in the manuscript: “To date, only a single study by Furukawa et al. has confirmed the presence\nof ribose and other aldopentoses in meteorites, highlighting current limitations in our ability to detect\nand understand sugar inventories in extraterrestrial materials.”\nL56-60: “This concern ... sample processing.” These sentences should be deleted because they would\ngive a negative impression to readers, as if all returned samples have been contaminated. Even without\nthese sentences, it makes sense to readers.\nResponse: We appreciate the reviewer’s concern regarding the tone of these sentences and the\npotential for readers to interpret them as suggesting widespread contamination of returned samples.\nThis was not our intention. Rather than casting doubt on the integrity of all samples, our goal was to\nemphasize the analytical challenge inherent in distinguishing indigenous organic compounds from\npossible terrestrial contaminants—an issue relevant to both meteorites and returned samples, even\nwhen the latter are collected under stringent conditions.\nWe believe it is important to highlight this concern explicitly to underscore the need for careful\ncontamination control and verification in future missions, without implying that current efforts are\ninsufficient. To ensure the tone is balanced and constructive, we have revised the paragraph.\nRevised in the manuscript: “A major challenge in analyzing prebiotically relevant organics such as\namino acids and sugars from astrophysical samples lies in confirming their extraterrestrial origin, due\nto the ever-present risk of terrestrial contamination. While meteorites are often subject to terrestrial\nweathering and potential microbial colonization prior to analysis30,31, even returned samples—such as\nthose from (162173) Ryugu and (101955) Bennu—despite being collected under meticulously\ncontrolled conditions by JAXA’s Hayabusa2 and NASA’s OSIRIS-REx missions31–34, require meticulous\nhandling and verification protocols to confidently assess indigenous organics.”\nWe hope this revised version clarifies our intent and presents the issue in a more neutral and\ninformative manner.\nL71-73: As for arabinose in NWA 801, Furukawa et al. (2019) did not report the d13C value due to the\nsignificant contribution by the co-eluting peak. However, they also claimed that arabinose and ribose\nin Murchison and ribose in NWA 801 are not significantly affected by their co-eluting peaks. It seems\nto me that the sentence here is based on the current author’s subjective opinions only. Hence, the\nsentence in Lines 71-73 should be deleted.\nResponse: We thank the reviewer for this important clarification. We have revised the sentence to\nmore accurately reflect the findings of Furukawa et al. (2019) and now specifically mention only\narabinose in NWA 801, for which a δ¹³C value could not be reported due to chromatographic\ninterference. We have removed any reference to ribose, in line with the original authors’ conclusions.\nThe revised sentence now reads: “In particular, in the only confirmed detection of sugars in\nmeteorites, Furukawa et al. (2019) reported that the accuracy of the carbon isotope measurement for\narabinose in NWA 801 was limited by a significant co-eluting peak, preventing reliable δ¹³C\ndetermination.”\nWe would also like to emphasize that our intention was by no means to diminish the important work\nof Furukawa et al., but rather to highlight the analytical challenges posed by such complex\nextraterrestrial samples—particularly for isotopic measurements, quantification, and compound-\nspecific resolution. We hope this clarification and revision adequately address the reviewer’s concern.\nL87: This should be deleted since this is a repetitive sentence of L80-82.\nResponse: This has been corrected as suggested.\nL90-92: This sentence is too strong since it is just based on the author’s assumption.\nResponse: We thank the reviewer for pointing this out. To address this and avoid overstating the\nconclusion, we have revised the sentence by replacing “show” with “indicate,” which better reflects\nthe tentative nature of our interpretation based on the estimated quantities. We believe this wording\nmore appropriately conveys that our observation is suggestive rather than conclusive, in line with the\nuncertainties inherent in sugar recovery and quantification.\nRevised in the manuscript: “The estimated quantities of individual sugar enantiomers indicate that\nsugar abundances are at least comparable to those of C₄–C₅ amino acid enantiomers in the same\nsamples.”\nL103: Which previous studies do the authors point out? Cite some references here.\nResponse: We appreciate the reviewer’s suggestion and have updated the text to explicitly cite\nrelevant references to support the key steps of our protocol.\nRevised in the manuscript: “Key to this methodology is a mild extraction protocol employing\nultrasonic-assisted extraction (temperature <20°C, neutral pH, and 10-minute sonication intervals) to\nprevent thermal degradation of sugars [Larralde et al., PNAS 92, 1995]. An ion exchange\nchromatography (IEC) step was employed to remove inorganic ions (e.g., Fe²⁺, Fe³⁺, and Mg²⁺)—major\ncomponents of chondritic mineral matrices that interfere with subsequent derivatization and\nchromatographic protocols [Burton et al. Chem Soc. Rev. 41, 2012; Simkus et al., Life 9, 2019]—and to\nseparate neutral sugars from amino acid zwitterions [Burton et al. Chem Soc. Rev. 41, 2012]. This\nseparation allows for tailored derivatization procedures and chromatographic conditions specific to\neach molecular class [Pepino et al. J. Sep. Sci. 45, 2022; Garcia et al. Talanta 271, 2024], enhancing\nboth sensitivity and selectivity in their analyses”.\nL119: “MBA” is appropriate as an abbreviation of methyl boronate?\nResponse: We thank the reviewer for their attention to detail. In our manuscript, we initially used\n“MBA” as an abbreviation for methylboronic acid derivatives, following precedent in the literature\nwhere this abbreviation has been used to describe derivatives formed through reactions with\nmethylboronic acid. While we believe the abbreviation is appropriate and practical for repeated use,\nwe recognize that it is not reused in the main text. Therefore, to maintain clarity and avoid\nunnecessary abbreviations, we have removed “MBA” from the main text and now correctly refer to\nmethylboronic acid esters in full. The abbreviation remains defined at its first mention in the Methods\nsection for consistency.\nL124, “significantly above the procedural blank levels”: This sentence is overstated.\nResponse: We have rephrased the sentence as follows:\nRevised in the manuscript: “Despite the limited sample quantity of 17.5 mg of pristine asteroid\nmaterial and the challenges associated with the extraction and analysis of sugars from extraterrestrial\nmaterial, we unambiguously detected both enantiomers of arabinose and xylose in Ryugu combined\nextracts (A0478 and A0483) in an enantiomeric composition distinct from that of the procedural blank.”\nL128, “near-racemic ratio (D/L ~ 1.0)”: This sentence is also overstated since no blank control has been\ndone.\nResponse: This sentence has been rephrased as follows:\nRevised in the manuscript: “Resolved D- and L-enantiomers of arabinose in the Ryugu sample show a\nslight excess of the L-form (D/L ≈ 0.67) (Fig. 2A), in contrast to the procedural blank (PB) which showed\na strong predominance of non-biologically less abundant D-arabinose (Fig. 2B, D/L ≈ 2.36).”\nFigure 2: In the PB data, not only L-Ara but also D-Ara (~34.10 for 1D, =1.8 for 2D) should be present,\nalthough the peak intensities vary significantly between D and L enantiomers, possibly due to the\nbiological contamination of L-Ara and the contamination from the standard reagent of D-Ara (if the\nauthors use the “expansion” technique as used in Figure 6a, this peak should be observed more clearly).\nThe presence of D-Ara in PB should be evaluated in more detail. Since the range of the color bar for PB\n(60154-300000) is significantly different from that for the Ryugu (11835-41561), the D-Ara abundance\nin PB may be significantly underestimated. Based on the color bar, the abundance of D-Ara in PB may\nbe ~100,000 or something like that. Assuming the recovery of 30% for Ara (Line 150), the possible\nabundance of D-Ara contributed to the Ryugu data is ~30,000, which is comparable to that of D-Ara in\nthe Ryugu data. Also, as for L-Ara, the abundance in the PB (300,000) may be able to explain the\nabundance in Ryugu, assuming again that the recovery is ~30%.\nFigure 3: Since the peak height for D-Xyl in PB looks much higher than that in Ryugu, the authors should\nevaluate the possible contribution from the contamination to the sample peak. Also, L-Xyl should be\npresent in PB, although its contribution seems less dominant compared to D-Ara in PB (Figure 2B). The\ndetection of L-Xyl, as well as that of D-Ara, in PB strongly suggests that there are multiple\ncontamination sources, such as terrestrial biology and standard reagents in the present study. Without\nsuch evaluation, it is hard to accept the author's statement that sugars are detected in the Ryugu\nextract.\nFigure 4: Why are Ara and Xyl, whose detections in PB are shown in Figure 5, not observed in the PB\ndata? Also, the detection of L-ribose and L-xylose in PB indicates the incorporation of their standard\nreagents.\nFigure 5: D-Ara should be present in the PB, although not indicated in the chromatogram. The peak\nintensity of D-Ara in the PB is ~100,000 or so. Assuming the recovery of 30% for Ara, the contribution\nof the contamination to the Orgueil data seems very high.\nFigure 6: The presence of L-Xyl is highlighted in an insert, which can visualize the small peak for L-Xyl.\nThis technique should be applied to the PB data; D-Ara in Figure 2, L-Xyl in Figure 3, D-Ara in Figure 5,\nand L-Xyl in Figure 6. The color in the insert does not seem to correspond to the color bar. Please modify\nit. Also, “Orgeuil” in the title is a typo.\nGrouped response: We thank the reviewer for their constructive criticism. In response to the general\ncritics raised by all reviewers, we have worked on thorough evaluation of the sources and level of\ncontamination of sugars introduced throughout our analytical protocol in order to support the\nidentification of their origin in the asteroid Ryugu and Orgueil meteorite samples. We performed a\nthorough systematic study of the contamination sources by comparing the levels of contamination in\nour reagent blanks with those of our procedural blanks in the presence and absence of SiO . SiO was\n2 2\nselected to simulate the matrix as it is one of the most abundant mineral constituents of Ryugu and\nOrgueil, and is stable when heated to 500 C. As can be seen in Supplementary Figure 8 below, we\npinpointed the main source of our sugar contamination to be the reagents used for sugar\nderivatization. As this contamination source cannot be easily eliminated, we consider it essential to\nmonitor and report the level of contamination in our procedural blanks and thoroughly investigate\nthe impact of a closely resembling mineral matrix on the recovery of sugars, which is the subject of a\nmanuscript currently in preparation and outside the scope of the present study.\nSupplementary Figure 8: Comparison of normalized chromatographic peak areas for arabinose (m/z\n84) and xylose (m/z 97) enantiomers, detected as methylboronic acid esters, across the reagent\nblank, procedural blanks (±SiO matrix), and Ryugu fragments. The chromatographic peak area of\n2\nthe internal standard methyl laurate (c = 10⁻6 M) in m/z 74 ion chromatogram was used as a reference\nfor normalization. The error bars represent a standard deviation of three replicate injections for\nthe procedural blanks and eight replicate injections for Ryugu. The error bars are not reported\nfor the reagent blank as it was injected just once.\nDespite the non-negligible level of contamination introduced throughout the analytical protocol\ncompared to the amount of sugars extracted from the limited amount of the asteroid Ryugu sample,\nit is evident from Supplementary Figure 8 that the enantiomeric composition of arabinose in the\nasteroid Ryugu fragments significantly differs from those of the reagent/procedural blanks, suggesting\npotential extraterrestrial origin of some of the arabinose content in the Ryugu fragments. If all\narabinose in the Ryugu extracts was introduced during the extraction/derivatization, the enantiomeric\nratio would be expected to resemble very closely the one of our procedural blanks. In the case of\nxylose, the very low quantities in the Ryugu extracts do not enable us to unambiguously distinguish its\norigin when compared to the procedural blanks and future studies are necessary to provide further\ninsights.\nDespite the challenges of limited asteroid sample availability and analytical difficulties associated with\nthe extraction and analysis of sugars, we provide strong evidence that at least some of arabinose in\nthe Ryugu fragments very likely has a different origin than the one in the procedural blanks. The\nimpossibility to carry out isotopic analysis with such small sample quantities does not allow a priori to\ndraw definitive conclusions about its extraterrestrial origin, but the detection of near-racemic amino\nacids strengthens the arguments of the potential extraterrestrial origin of arabinose. Therefore,\nalthough caution should be exercised in the interpretation of the present results especially when it\ncomes to the enantiomeric excess and absolute quantification, we consider it to be essential to share\nthe present results with the community to support and direct future research on the detection of\ncarbohydrates in extraterrestrial samples, which has remained a challenge so far. In accordance with\nthe above points, we have revised the following sections of the manuscript to as best as possible\naddress and clarify the points raised by the reviewer:\nRevised in the manuscript: “Despite the limited sample quantity of 17.5 mg of pristine asteroid\nmaterial and the challenges associated with the extraction and analysis of sugars from extraterrestrial\nmaterial, we unambiguously detected both enantiomers of arabinose and xylose in Ryugu combined\nextracts (A0478 and A0483) in an enantiomeric composition distinct from that of the procedural blank\n(Supplementary Figure 8). If all sugar content in the Ryugu extracts was introduced throughout the\nanalytical procedure, one would expect the enantiomeric composition to closely resemble the one of\nthe procedural blank.”\nRevised in the manuscript: “Xylose enantiomers were also successfully resolved in the Ryugu sample,\nshowing a pronounced predominance of the biological D-enantiomer (Fig. 3A). Unlike for arabinose,\nthe extremely low quantities of xylose in the Ryugu extract do not enable us to unambiguously\ndistinguish its origin when compared to the procedural blanks (Supplementary Figures 7 and 8), which\nmakes its assignment much more elusive. Notwithstanding, the present detection of xylose in the\nRyugu extracts sets a precedent for future studies, where improved extraction efficiency is very likely\nto lead to more conclusive results.”\nRevised in the manuscript: “To better constrain the origin of the detected sugars, we conducted a\ndetailed assessment of potential contamination sources in our procedural blanks. We compared sugar\nlevels in the reagent blank with those in procedural blanks prepared without and with the SiO₂ matrix,\nwhich indicated that the major contribution to contamination arose during the derivatization step,\nspecifically from the derivatization reagents. (Supplementary Note 2, Supplementary Figures 6–8).”\nRevised in the manuscript: \"Importantly, these recovery tests provide the first evidence of sugar-\nspecific interactions with the carbonaceous chondrite matrix, highlighting the need for developing\nstandardized protocols employing closely resembling meteorite matrix in procedural blanks so that a\nblank-correction can be made to accurately quantify absolute extraterrestrial abundances and\nenantiomeric excesses. This is particularly important for drawing comparisons between the organic\ncontent in distinct parent bodies.”\nRevised in the manuscript: “Both were detected in Ryugu aggregates, even though xylose with yet\nelusive origin. Arabinose exhibited significantly distinct enantiomeric composition as opposed to the\nprocedural blank.”\nFurthermore, we now highlight both enantiomers of arabinose and xylose in the procedural blanks in\nFigures 2 and 3, as well as show their respective mass spectra. We have also fixed the z-axis scales for\nthe detailed views of the chromatograms in Figures 2 and 3. Figures 5 and 6 were redundant and we\nremoved them from the manuscript, while we revised Figure 4. We also added “Supplementary Note\n2: Assessing the indigenous nature of sugars” to the Supplementary Information file.\n“Orgueil” has been corrected.\nL196: “same parent body” -> “same fragment”.\nResponse: This has been corrected as suggested.\nL199: sumarized -> summarized\nResponse: This has been corrected as suggested.\nL197-208, amino acids in Ryugu: Some examples of the raw data (chromatograms of samples and\nblank, for example) for the detection of amino acids should be presented somewhere in the article.\nHow much is the recovery of major amino acids?\nResponse: Thank you for pointing this out. We have now included a two-dimensional gas-\nchromatogram of norvaline detected in the Ryugu fragments (Supplementary Figure 5). To keep the\nbalance between yours and another reviewer’s comments, who on the contrary suggested to shorten\nour discussion on amino acids, we would like to keep this part as succinct as possible. Importantly, we\nincluded the amino acid analysis in this manuscript only with the aim to highlight (i) the consistency\nof our analytical protocol with the previous studies, and (ii) the near-racemic nature of some of the\nbiological amino acids, which points to their extraterrestrial origin rather than biological\ncontamination. Furthermore, a separate manuscript on the development of the protocol for the\nsimultaneous analysis of amino acids and sugars, and the impact of the mineral matrix on their\nrecoveries is currently underway. Detailed analyses of the amino acids in the two samples along with\nchromatograms will be presented and thoroughly discussed there.\nRecovery data for the full protocol show that 17 of 27 amino acids had recoveries >78% from a spiked\nOrgueil matrix, with only three below 20%, with the diamino acids 2,4‑DAB and 2,3-DAP being the\nmost severely impacted. Such loss was attributed to strong matrix effects, as the application of the\nprocedure in the absence of the matrix yielded recoveries >60% for all compounds.\nDiscussion: Many sentences overlap with those in the Introduction. The first two paragraphs are mostly\na summary of previous studies.\nResponse: We thank the reviewer for this helpful observation. In response, we have revised and\nshortened the opening paragraphs to reduce redundancy with the Introduction. The updated version\nnow provides a more concise context while emphasizing the novelty and relevance of our findings.\nWe hope the revised text better reflects the focus and originality of our study.\nRevised in the manuscript: “Sugars are increasingly recognized as key prebiotic molecules due to their\nfundamental biological roles. Although laboratory simulations have demonstrated that sugars can\nform under astrophysically relevant conditions16–19, only a single report of ribose and related aldoses\nin meteorites has suggested their potential delivery to early Earth.¹⁵ Our detection of individual sugar\nenantiomers alongside amino acids in both the pristine Ryugu asteroid and the Orgueil meteorite\nprovides new and complementary evidence supporting this hypothesis.”\nL250: As pointed out earlier, the ultrasonic-assisted extraction and ion-exchange chromatography\nhave already been applied in Furukawa et al. (2019). Please focus on the advantages of using GCxGC.\nResponse: We fully agree with the reviewer’s observation. Accordingly, we have revised the\nintroductory paragraph and removed the original sentence referencing ultrasonic-assisted extraction\nand ion-exchange chromatography, which were previously applied by Furukawa et al. (2019). To\naddress your comment, we now emphasize the detection of individual sugar enantiomers to highlight\nthe added value and advantages of using enantioselective GC×GC in our study.\nL264: The proposed near-racemic nature of arabinose is not guaranteed due to the lack of any\ncontamination control.\nL266, “only biological enantiomers of both sugars were detected”: This contradicts the PD data as\nindicated above.\nGrouped response: We have modified the corresponding paragraph as follows:\nRevised in the manuscript: “In our study, arabinose and xylose were the sugars with the highest\nrecovery rates, as validated by spiked Orgueil matrix tests (Table 1). Both were detected in Ryugu\naggregates, even though xylose with yet elusive origin. Arabinose exhibited significantly distinct\nenantiomeric composition compared to the procedural blank, pointing to the distinct origin of at least\na portion of the arabinose detected in Ryugu.”\nL273-274: “D-xylose/arabinose” may be “D-xylose/L-arabinose”. This sentence seems to contradict the\nauthor’s claim that “The near-racemic proportions observed in several of the detected sugars support\ntheir abiotic and potentially extraterrestrial origin” in L85-87.\nResponse: Thank you for pointing this out. We have fixed the sentence in L273-274 as suggested and\nmodified the sentence in L85-87 as follows:\nRevised in the manuscript: “The distinct enantiomeric distributions compared to the procedural\nblanks observed in several of the detected sugars support their potentially extraterrestrial origin.”\nL278: I’m confused. The authors presented the concentration of sugars in Ryugu in Table 1. However,\nthis is an appropriate conclusion.\nResponse: We appreciate the reviewer’s observation and agree that the previous text may have\ncaused confusion. We have clarified in the revised manuscript that only the Orgueil samples allowed\nfor reliable quantitative analysis, while the Ryugu concentrations remain below quantification limits\nand are reported as rough estimates only. Accordingly, we specified that the comparison with previous\nliterature values—particularly those from Furukawa et al. (2019)—was made exclusively for Orgueil,\nwhere sugar concentrations were above the quantification threshold. Furthermore, we have included\nthe following footnote under Table 1:\nRevised in the manuscript: “The values should be considered as estimates as the concentrations are\nbelow the limits of quantification.” Moreover, we modified the following sentence in the manuscript:\n“The low peak areas for both sugars detected in the Ryugu sample prevented accurate quantification\nand determination of enantiomeric excess, hence the values reported in Table 1 should be considered\nonly as estimates.”\nL285-286: Why can the presence of C6 sugars not be excluded?\nResponse: We thank the reviewer for this important question. We have clarified the sentence in the\nmanuscript to explain that our derivatization method does not allow for the detection of hexoses like\nglucose. As such, their presence cannot be excluded. This is particularly relevant since previous\nlaboratory simulations—both of interstellar ice analogues (refs. 16–19) and planetary/mineral\nanalogues (refs. 20–22)—have proposed the formation of C₆ sugars such as glucose. We now\nemphasize that the detection of such sugars may depend heavily on the analytical strategy employed.\nRevised sentence in the manuscript: “Moreover, our derivatization approach does not allow for the\ndetection of hexoses like glucose. However, their presence—suggested by both interstellar ice\nanalogues and planetary/mineral analogues—cannot be excluded, and their detection may depend\nheavily on the analytical strategy used.”\nL293: NH3 in Ryugu is much less than Orgueil. Ref 59 did not mention it. Yoshimura et al. (2023) Nature\nCommunications, 14, 5284, reported the low concentration of NH3 in Ryugu. Please refer to Ref 14\nwhich compares the concentration of NH3 in various samples.\nResponse: We thank the reviewer for this comment. We have replaced reference 59 (Oba et al., 2023)\nin the original manuscript with Yoshimura et al. (Nature Communications 14, 2023), which provides\ndirect evidence of ammonium salts in Ryugu samples. We have also added the supporting study by\nGlavin et al. (Nature Astronomy, 2024) for further contextualization regarding ammonium. We also\nremoved any discussion of ammonia (NH₃) from the manuscript, clarifying that the focus should\ninstead be on ammonium (NH₄⁺) as evidence of low-temperature aqueous activity on Ryugu and its\npotential impact on sugar formation and degradation.\nL296-314: Without blank corrections, the discussion in these paragraphs does not make sense at all.\nResponse: We partly disagree with the reviewer that the concentration and enantiomeric excess\nvalues of amino acids detected in the extraterrestrial material should be blank corrected. This is\nbecause neither the procedural blank with the SiO₂ matrix nor the one without fully matches the\ncomplex mineralogical and chemical composition of Ryugu/Orgueil, which can affect the composition\nand recovery of the detected amino acids. Hence subtracting the procedural blank levels could skew\nthe results in a yet-unknown way. Consequently, we consider it to be more appropriate to present the\n‘raw data’ of amino acids detected in both samples (Ryugu and Orgueil). However, for better\ncomparison with the existing literature on amino acids in Ryugu and Orgueil, we followed common\npractice and have also added the procedural blank–corrected quantities to Table 1. Nevertheless, we\nstrongly recommend that these absolute values should be interpreted carefully, given the current\nlimitations of the procedural blanks typically employed in the research community.\nIn the future, thorough studies of the impact of spiked reference matrices, closely resembling the ones\nof extraterrestrial matter, on sugar and amino acid recoveries, are necessary to be able to correctly\naccount for procedural blank contamination. This is, however, beyond the scope of the present study\nand a separate manuscript that aims to address this is currently underway. Standardized protocols\nshould be then used across all studies in the community to enable meaningful comparisons of\nsugar/amino acid content between distinct parent bodies.\nTable 1: Show the blank-corrected values for sugars in Ryugu and Orgueil. Also, footnote d should be\ndeleted since d13C is not relevant to the data in this table. This statement is merely an attempt to\ndowngrade prior studies.\nResponse: Thank you for your suggestions, but we disagree with the reviewer that the concentration\nand enantiomeric excess values of sugars detected in the extraterrestrial material should be blank\ncorrected. For detailed explanation see the comment above.\nRegarding original footnote “d” (now “e”), we thank the reviewer for pointing this out. We fully agree\nthat it is important to avoid any phrasing that might be interpreted as diminishing the value of prior\nstudies. Our footnote was not intended to downgrade the work of Furukawa et al. (2019), but rather\nto highlight the analytical limitations and the importance of isotopic measurements in supporting the\nextraterrestrial origin of chiral organics. Since the δ¹³C values were either not significant or could not\nbe determined in that study, we intended to raise awareness of the risk that terrestrial biological\ncontamination may influence the observed concentrations. We hope this approach is acceptable, but\nwe remain open to alternative suggestions if preferred. We have now included also the following\nfootnote regarding our study under Table 1:\nRevised in the manuscript: “The values should be considered as estimates as the concentrations are\nbelow the limits of quantification.” Moreover, we modified the following sentence in the manuscript:\n“The low peak areas for both sugars detected in the Ryugu sample prevented accurate quantification\nand determination of enantiomeric excess, hence the values reported in Table 1 should be considered\nonly as estimates.”\nTable 2: In the column of A0106, the superscript “a” may be wrong. Also, how did the authors perform\nblank correction? Are the sample data corrected using that for PB without minerals? Please clarify. If\nso, such a blank correction is not appropriate because the same analytical procedures are not applied\nto both samples and PB. Show the blank-corrected values for amino acids in Orgueil, too. Or, show only\nblank-corrected values for both Ryugu and Orgueil. Negative values after the subtraction of PB should\nbe an indicator for the incorporation of many contaminants during analytical procedures. How do\nthe authors explain this?\nTable 3: Enantiomeric compositions should be calculated by their brank-corrected concentrations.\nResponse: We thank the reviewer for highlighting these points. Naraoka et al. did not specify in either\nthe main manuscript or in the Supplementary Information file that a blank correction was carried out\nfor their data. Thence, we leave the superscript “a” for this study.\nAs argued above, we chose not to apply blank correction to the concentration and enantiomeric\nexcess values of sugars detected in the Ryugu and Orgueil fragments analyzed in this study. The sugars\nidentified as indigenous to the Ryugu and Orgueil samples clearly exceed the levels observed in our\nprocedural blanks. Nevertheless, given the current uncertainty in fully accounting for recovery and\npotential contamination associated with the procedural blanks, we consider it important to openly\nacknowledge these limitations and to exercise caution when reporting quantitative data from such\nsamples.\nRegarding amino acids, the absence of any matrix in our procedural blanks without SiO₂ clearly led to\nthe negative values after blank subtraction, as you pointed out. However, we would like to emphasize\nthat our procedural blanks should not be mistaken for a simple reagent blank. All of our procedural\nblanks—both with and without SiO₂—were run through the entire protocol. The blanks without SiO₂\nwere processed in parallel to best monitor potential contamination on that specific day, using the\nsame chemicals under identical environmental conditions. We fully agree, and this is also evident from\nour detailed contamination/recovery study (conducted in parallel and still ongoing, with results to be\nreported in a separate manuscript on this important issue), that the presence of a matrix tends to\nretain not only the targeted molecules but also any biological trace contamination. The key challenge\nremains to best reproduce the mineralogical composition of each carbonaceous chondrite—a task\nthat is by no means trivial.\nSupplementary Information\nL129-, Ion exchange chromatography: It seems that the cold and hot water extracts are not acidified\nbefore IEC, which results in the zwitterionic forms of amino acids in the extract. The authors mentioned\nthat they adapted a protocol from Simkus et al. However, the author’s protocol is different from that\nshown in Simkus et al. and Amelung and Zhang (2001) which Simkus et al. referred to in their paper,\nin the use of ethanol and methanol in the pretreatment. Also, the use of H2O/MeOH for the wash of the\ncolumn walls is different from these earlier papers. It seems to me that the use of methanol and\nethanol for the treatment for cation-exchange chromatography is not so common. Were sugars and amino\nacids recovered well in this protocol? How much are their recoveries in this protocol only? Please clarify\nthem.\nResponse: We thank the reviewer for raising this important question. Our protocol was specifically\noptimized to avoid racemization of sugars and amino acids while preventing the introduction of\nunwanted cations (e.g., inorganic salts like Na⁺, K⁺, Ca²⁺, Mg²⁺, etc.), which could severely interfere\nwith the drying steps, derivatization, and gas chromatographic analysis. This is why acidification of the\nwater extracts was intentionally omitted as acid conditions are known to induce amino acid\nracemization and also because the use of HCl may induce the formation of salts such as NH₄Cl when\neluting with NH₄OH which would compromise GC performance.\nWe performed preliminary tests to assure that, despite neutral pH, amino acids bind effectively to the\ncation exchange resin while sugars are recovered. Recovery data of amino acids for the full protocol\nshow that 17 of 27 amino acids had recoveries >78% from a spiked Orgueil matrix, with only three\nbelow 20%. This loss was mainly attributed to strong matrix effects, as the IEC step, including the\nconcentration steps, in the absence of matrix yielded recoveries >60% for all compounds. For sugars,\nrecoveries were also >60% when the full protocol was applied in the absence of a matrix. We have\nupdated the main manuscript and SI to include this relevant information.\nRevised in section 1.5 of the Supplementary Note 1: “The water extracts from both cold and hot\nextractions (approximately 2.5 mL) were subsequently eluted through the columns in 200 μL portions\nwithout further acidification to prevent potential racemization of the amino acids. Prior recovery tests\nconfirmed the effective binding of amino acids to the cation exchange resin.”\nL217: Why sugars in Orgueil were analyzed in a way different from that applied to Ryugu extracts?\nResponse: We thank the reviewer for raising this point regarding the methodological differences,\nwhich indeed were a critical and necessary adaptation. It should be noted that the Orgueil extract was\nanalyzed before Ryugu. To ensure the best chromatographic performance after multiple injections of\nsamples from Orgueil, blanks, and standards over several weeks, an installation of a new\nchromatographic column was necessary. After replacing the first chromatographic column, the\nadaptation of the temperature programme of the secondary oven was necessary to keep optimal\noverall resolution and individual enantioseparation.\nIn addition to the differences in the protocol for chromatographic analysis, the extraction protocol for\nOrgueil had to be adapted too. The primary reason for the modified extraction protocol for the\nOrgueil sample was the tenfold larger sample mass available to us. While beneficial for detecting trace\ncompounds, this larger mass also introduced a proportionally larger amount of soluble inorganic ions\n(salts) and insoluble matrix components. To mitigate the severe interference this would cause during\nsubsequent pre-treatment and GC-MS analysis, we introduced an additional purification barrier by\nincreasing the quantity of resin and including a polyethersulfone (PES) syringe filter.\nWe have included a brief clarification in the Methods section of the SI to explicitly state the rationale\nfor the sample pre-treatment adaptation.\nRevised in section 1.5 of the Supplementary Note 1: “To accommodate the 10-fold higher matrix\nload, the procedure was upscaled and a total of six methanol extractions were performed.”\nL234-235: In the footnote of Table 1, the authors mentioned that the quantification values are\nuncorrected for procedural blanks. While, the description in these lines seems to contradict the\ndescription in Table 1. Please clarify.\nResponse: Thank you for highlighting this discrepancy. We have removed this sentence from the\nSupplementary Information file.\nL237, Supplementary Note 2: Regardless of the degree of recovery, there is no doubt that there are\nsignificant sugar contaminations incorporated into the sample during analytical procedures. What is\n(are) the source(s) of such significant contamination? Without evaluating contamination, the reported\nconcentrations of sugars and amino acids, as well as their ee, cannot be accepted as the native values\nfor Ryugu and Orgueil samples.\nResponse: We fully agree that it is very important to evaluate the sources and level of contamination\nof sugars introduced throughout our analytical protocol in order to support the identification of their\norigin in the extraterrestrial samples. Therefore, we performed a thorough systematic study of the\ncontamination sources and made corresponding changes to the manuscript as described above.\nReviewer #2 (Remarks to the Author):\nMajor comments:\nThis research investigated sugars in the sample of the carbonaceous asteroid Ryugu. The sample is\nextremely valuable, and the chiral separation of sugars represents a significant novel development.\nThus, this research is suitable for consideration in Nature Communications. However, I have several\nconcerns with this analysis, primarily related to the potential contamination of biological and unclear\nsources of sugars, which may be derived from a standard chemical mixture. Suppose this\ncontamination occurred outside of the sample solution, such as in the GC-MS injector. In that case, a\nrepeat analysis of the sample with a clean GC-MS system will provide a convincing result. However, if\nthis contamination occurred in the sample solution, I have no idea how to show the presence of\nextraterrestrial sugars in the Ryugu with this sample. Thus, the manuscript, at least in this form, is not\nsufficient to show that the Ryugu sample contains abiotic sugars.\n1. The central issue is the contamination of both D-sugars and L-sugars in the sample of Orgueil and\npotentially Ryugu. In this type of analysis, the procedural blank that undergoes the same conditions as\nthe sample is crucial for demonstrating contamination. The procedural blank of Orgueil shows\ncontamination of D-ribose, L-ribose, D-lyxose, and L-lyxose. Since L-ribose and L-lyxose are not\nbiological contaminants, this suggests that cross-contamination of the standard or sample occurred\nwith the procedural blank. I guess the contamination was from the standard because the significantly\nhigher abundance of ribose and lyxose than arabinose and xylose is not reasonable as abiotic sugars,\nand the relative abundance between sugars is different from that of the Orgueil. Given the presence of\ncross-contamination, the chromatogram of the Orgueil sample may be consistent with the sugar\ncomposition of the standard + biological contaminants. The author should explain considering this\npossibility, both in Ryugu and Orgueil. To discuss this possibility, the authors should show the\nchromatogram of the standard mixture.\nResponse: We thank the reviewer for highlighting these critical points. We fully agree that the\nenantioselective analysis of sugars represents a key novel step in the analysis of extraterrestrial\nsamples, both from the scientific point of view as it can shed light on potential astrochemical origins\nof homochirality, as well as it proves very useful in the process of analyzing the origin of sugars\ndetected in such samples. In response to the concerns raised by all three reviewers, we exploited the\nlatter one in determining the origin of the contamination sources introduced throughout our analytical\nprotocol. Therefore, we performed a thorough systematic study of the contamination sources by\ncomparing the levels of contamination in our reagent blanks with those of our procedural blanks in\nthe presence and absence of SiO . SiO was selected to simulate the matrix as it is one of the most\n2 2\nabundant mineral constituents of Ryugu and Orgueil, and is stable when heated to 500 C. As can be\nseen in Supplementary Figure 8 (below), we pinpointed the main source of our sugar contamination\nto be the reagents used for sugar derivatization. As this contamination source cannot be easily\neliminated, we consider it essential to monitor and report the level of contamination in our procedural\nblanks and thoroughly investigate the impact of a closely resembling mineral matrix on the recovery\nof sugars, which is the subject of a manuscript currently in preparation and outside the scope of the\npresent study.\nDespite the non-negligible level of contamination introduced throughout the analytical protocol\ncompared to the amount of sugars extracted from the limited amount of the asteroid Ryugu sample,\nit is evident from Supplementary Figure 8 that the enantiomeric composition of arabinose in the\nasteroid Ryugu fragments significantly differs from those of the reagent/procedural blanks, suggesting\npotential extraterrestrial origin of some of the arabinose content in the Ryugu fragments. If all\narabinose in the Ryugu extracts was introduced during the extraction/derivatization, the enantiomeric\nratio would be expected to resemble very closely the one of our procedural blanks. In the case of\nxylose, the very low quantities in the Ryugu extracts do not enable us to unambiguously distinguish its\norigin when compared to the procedural blanks and future studies are necessary to provide further\ninsights. Similar evidence for the unambiguous detection of sugars in the Orgueil fragment, specifically\nthe distinct contamination signatures observed in our procedural blanks versus the Orgueil sample is\npresented in Supplementary Figure 9.\nSupplementary Figure 8: Comparison of normalized chromatographic peak areas for arabinose (m/z\n84) and xylose (m/z 97) enantiomers, detected as methylboronic acid esters, across the reagent\nblank, procedural blanks (±SiO matrix), and Ryugu fragments. The chromatographic peak area of\n2\nthe internal standard methyl laurate (c = 10⁻6 M) in m/z 74 ion chromatogram was used as a reference\nfor normalization. The error bars represent a standard deviation of three replicate injections for the\nprocedural blanks and eight replicate injections for Ryugu. The error bars are not reported for the\nreagent blank as it was injected just once.\nDespite the challenges of limited asteroid sample availability and analytical difficulties associated with\nthe extraction and analysis of sugars, we provide strong evidence that at least some of arabinose in\nthe Ryugu fragments very likely has a different origin than the one in the procedural blanks. The\nimpossibility to carry out isotopic analysis with such small sample quantities does not allow a priori to\ndraw definitive conclusions about its extraterrestrial origin, but the detection of near-racemic amino\nacids strengthens the arguments of the potential extraterrestrial origin of arabinose. Therefore,\nalthough caution should be exercised in the interpretation of the present results especially when it\ncomes to the enantiomeric excess and absolute quantification in space, we consider it to be essential\nto share the present results with the community to support and direct future research on the\ndetection of carbohydrates in extraterrestrial samples, which has remained a challenge so far.\n2. The amounts of D-xylose and L-arabinose in the procedural blank for the Ryugu sample should be\nlisted in the Table. The abundance of D-xylose in Ryugu maybe comparable to that detected in the\nprocedural blank. They should be compared.\nResponse: We agree that a clearer evaluation of the significance of the sugars detected relative to our\nprocedural blanks was needed. Therefore, we have added detailed contamination data for each\nindividual sugar identified in the Ryugu fragments (arabinose and xylose, Supplementary Figure 8) and\nin the Orgueil meteorite (4 aldopentoses + ribulose, Supplementary Figure 9). Nevertheless, our\nspiking experiments clearly demonstrate the negative impact of the meteorite matrix on sugar\nrecovery, and given that the SiO₂ used in our procedural blanks does not adequately replicate the\ncomplex nature of the Ryugu or Orgueil matrices, we chose not to apply blank corrections to the\nabsolute quantities or enantiomeric excess values of sugars detected in the extraterrestrial samples,\nas such corrections could bias the results in an unknown manner. Rather than applying corrections,\nwe present the absolute values of sugar contents in the Ryugu and Orgueil samples, with the caution\nthat our discussion should be considered when interpreting these preliminary quantitative data.\n3. L268-269 and table 1: The authors describe that “Among these, ribose, lyxose, and ribulose showed\nracemic distributions, consistent with an extraterrestrial origin.” However, near-racemic ribose and\nlyxose are also detected in the procedural blank, indicating that the detected ribose and lyxose are\npossible contaminants from the standard. If we suppose that the amounts of D-arabinose and L-xylose\nare authigenic of Orgueil, why do ribose and lyxose (rare sugar) have 20-30 times greater amounts?\nAs the author shows, the recovery of ribose is only 4%, indicating that ribose is present at a\nconcentration more than 300 times that of arabinose. This is not reasonable. The compositions of\nsugars in the procedural blank implies that the same source of contamination occurred more\nsignificantly to Orgueil.\nResponse: We respectfully disagree with the conclusion that ribose and lyxose detected in the Orgueil\nfragment can be attributed solely to contamination from the standard. While we do not exclude\npossible biological or laboratory contributions to individual sugars—including ribose and lyxose—we\nemphasize that the sugar levels measured in Orgueil significantly exceed those observed in our\nprocedural blanks (Supplementary Figure 9). Although the exact source of each potential contaminant\nremains to be determined, we are confident that at least part of the detected sugars is indigenous to\nthe Orgueil fragment.\nThe detection of lyxose, in particular, is noteworthy. Its extremely limited distribution in biology\nmakes its recovery—especially with racemic or near-racemic compositions—consistent with a\nsubstantial abiotic contribution. By contrast, the predominance of the biologically favored\nenantiomers of arabinose and xylose in our samples points to a higher likelihood of contamination.\nThis is in agreement with the broader biological distribution of these two aldopentoses (see Table\nbelow), as well as with prior reports documenting their higher contamination potential. One possible\nfactor is that pollen and dust—likely the primary contamination sources in our laboratory—would be\nexpected to introduce disproportionately high levels of arabinose and xylose (see Table below).\nThe case of ribose is more complex. Precisely because ribose plays such a central role in biology, we\nrefrained from overinterpreting its relative abundance in this single fragment. That said, we caution\nagainst drawing definitive mechanistic conclusions at this stage. Without replicate analyses and\ndedicated recovery experiments, it is premature to ascribe the observed abundances to specific\nprocesses with scientific certainty. However, the racemic nature of ribose, combined with\nconcentrations significantly exceeding blank levels, provides strong evidence for its indigenous origin\nin the Orgueil fragment.\nRelative Abundance of Aldopentoses in Biology and Plants (Implications for Contamination)\nGeneral Biological Systems\nAldopentose Plants (cell walls, tissues) Contamination Risk Indicator\n(microbes, biomass)\nVery high – central to RNA, Moderate – mainly in Strong contamination marker if\nRibose DNA (via deoxyribose), ATP, nucleic acids, not bulk high levels are present\nNADH, cofactors polysaccharides (especially microbial sources)\nVery high – dominant in Strong indicator of plant-derived\nModerate – present in some\nXylose xylans of hemicellulose contamination (dust, fibers,\nmicrobial polysaccharides\n(major plant sugar) pollen)\nModerate – found in\nHigh – common in Often co-occurs with xylose;\nArabinose bacterial cell walls and\narabinoxylans and pectins points to plant contamination\nglycans\nVery rare – restricted to a\nUnlikely to result from terrestrial\nfew bacterial\nLyxose Essentially absent contamination; potential marker\npolysaccharides and\nof non-terrestrial processes\nmetabolites\nIn summary biological contamination sources specifically for aldopentoses are as follows:\n Biological contamination (general biomass): Ribose ≫ Xylose > Arabinose ≫ Lyxose\n Plant contamination: Xylose ≫ Arabinose > Ribose ≫ Lyxose\n4. The data on ribulose is missing. This should be shown.\nResponse: We appreciate the reviewer’s careful attention to this important point. We have now\nincluded the chromatograms for ribulose in the Orgueil meteorite sample and the corresponding\nreference standard in Figure 4 (revised manuscript). Additionally, the comparison of the ribulose\nenantiomers across the procedural blanks ±SiO has been added to the Supplementary Information\n2\n(Supplementary Figure S10) to confirm its identification. These updates ensure full transparency and\nsupport the validity of our detection.\n5. The chromatograms and abundance of ribose and lyxose in Ryugu should be shown.\nResponse: Unfortunately, ribose and lyxose were below the detection limits in the Ryugu fragments.\nCompared to arabinose and xylose, they exhibited lower recovery rates under our extraction\nconditions and were therefore not detected. However, their absence in our data does not rule out\ntheir presence at trace levels below the current analytical sensitivity.\n6. The authors underlined the novelty and advantage of this extraction repeatedly. However, the\nultrasonic-assisted room temperature extraction has been conducted in previous studies with water\nand 2% HCl (Cooper et al. 2001 and Furukawa et al., 2019). The clear difference in this study is\nextraction by methanol. However, extraction of sugars with methanol is not effective, owing to their\nlow solubility compared to water and HCl. For example, Alessandro et al., (Alessandro C. Galvão,\nMaicon R. Zangalli, Pedro Felipe Arce, Weber S. Robazza, Solubility of fructose and sucrose in mixtures\nof methanol and water: Experiment and application of equations of state and activity coefficient\nmodel, Journal of Food Engineering, 369, 2024,) shows that the solubility of fructose in methanol is less\nthan 10% in water. The loss of the extraction is evaluated in this method using the addition of sugars\nto Orgueil. Thus, this is not an essential problem, but clearly this extraction is not the\nadvantage but disadvantage from previous studies.\nResponse: We thank the reviewer for this insightful comment. While the reviewer cites studies on the\nsolubility limit of C6 fructose and sucrose disaccharide in methanol, these sugars were not the target\nof our analysis. We focused on small C3-C5 sugars which are highly soluble in methanol. In addition,\nour target analytes are trace-level meteoritic sugars, with expected concentrations many orders of\nmagnitude below solubility limits of these sugars in methanol. Even with its lower solubility, methanol\ncan dissolve micromolar or nanomolar quantities of sugars with ease. Importantly, we selected\nmethanol as the extraction solvent for sugars because it has several analytical advantages over water.\nMethanol has been shown to limit the extraction of inorganic ions from the meteorite matrix\n(Timoumi et al. Ultrasonics Sonochemistry 103, 106775 (2025)—reducing interference during\ndownstream analyses—while effectively solubilizing a broad range of polar organic compounds,\nincluding sugar-related molecules\nIn an FT-ICR mass spectrometry study of the Murchison meteorite, methanol extracts yielded\nsignificantly more CHO-containing molecular formulas than water extractions—demonstrating its\nsuperior efficiency for extracting soluble polar organics (including polyols) while minimizing matrix-\nderived salts (Schmitt-Kopplin et al. PNAS 107, 2763 (2010)). Furthermore, Schmitt-Kopplin et al.\n(2023) demonstrated that methanol extracts from Ryugu contained abundant CHO-rich and polyol-\nlike compounds, reinforcing its suitability for targeting sugars in extraterrestrial materials\n(https://www.nature.com/articles/s41467-023-42075-y)\nWe consider, therefore, that the use of methanol is an \"advantage\" and not a disadvantage of our\nmethod as it is more compatible with salt-sensitive analytical workflows. Nevertheless, in view of the\nlow overall sugar recoveries, we intend to test alternative extraction protocols in future work and will\nincorporate the reviewer’s advice into our experimental design.\n7. The table 2 shows the abundance of amino acids and their blank-subtracted values. The values of\n“UNH(a)” represent sample + contaminants and the value with “UNH(b)” are real extraterrestrial\namino acids. Many of the values in “b” is n.v., meaning that they are smaller than the blank. This means\nthat the procedural blank does not work as procedural blank.\nResponse: Thank you for raising these points. We fully agree that our procedural blank does not fully\nsimulate the impact (degradation, recovery, etc.) of the real Ryugu and/or Orgueil mineral matrix.\nTherefore, we do not consider the blank-corrected data to be true ‘extraterrestrial abundances’.\nSubtracting the procedural blank levels when omitting or not resembling closely the matrix skews the\nabundance values in a yet-unknown way. Hence, we consider it more appropriate to present the\nraw data’ of amino acids detected in both samples (Ryugu and Orgueil). However, for better\ncomparison with the existing literature on amino acids in Ryugu and Orgueil, we followed common\npractice and have also added the procedural blank–corrected quantities to Table 1. Nevertheless, we\nstrongly recommend that these absolute values should be interpreted carefully, given the current\nlimitations of the procedural blanks typically employed in the research community.\nIn the future, thorough studies of the impact of spiked reference matrices, closely resembling the ones\nof extraterrestrial matter, on sugar and amino acid recoveries, are necessary to be able to correctly\naccount for procedural blank contamination. This is, however, beyond the scope of the present study\nand a separate manuscript that aims to address this is currently underway. Standardized protocols\nshould be then used across all studies in the community to enable meaningful comparisons of\nsugar/amino acid content between distinct parent bodies.\n8. The manuscript should show reproducibility of amino acid analysis. If they consider the\nreproducibility, several values in the “b” column may be not reliable. For example, D-Ala was detected\nin the sample and blank at 0.326 and 0.378, respectively. If the reproducibility is 10%, the difference is\nnot clear. This may happen also for 2-ABA.\nResponse: Thank you for highlighting this point. We agree that in order to assess the reliability of the\npresented data it is important to include the error bars. In response, we have now added an extended\nversion of Table 2 in the Supplementary Information file (Supplementary Table 1) which includes the\nerror bars reflecting the repeatability of the replicate injections of our samples. However, we prefer\nto keep the ‘compact’ Table 2 as it is in the main text to facilitate the comparison of amino acid\nabundances among different studies.\n9. The amounts of amino acids in the procedural blank for Orgueil should be shown in the table.\nResponse: Following the reviewer’s comment and in line with current literature practice, we have\nincluded in Table 2 both the raw amino acid data and the procedural blank-corrected values for\nOrgueil.\n10. Any meteorite has the potential for contamination from sampling to curation. To prevent this effect\nin previous studies of sugars, meteorites were trimmed to remove potentially contaminated surfaces\n(Cooper et al. 2001 and Furukawa et al., 2019). Did the authors trim Orgueil to remove contamination,\nor did the authors use an inner part of the original fragment of Orgueil? The data of Orgueil analysis\nin this manuscript shows contamination of biological sugars and amino acids. If they analyzed with\nexposed surface, this could be the primary reason of biological contamination.\nResponse: We thank the reviewer for this critical point. Our allocation request to the Muséum\nNational d’Histoire Naturelle (MNHN) specifically asked for an interior fragment to avoid surface\ncontamination. The museum provided the sample accordingly and we did not perform any further\ncleaning or physical trimming commonly used for other meteorites as it is impossible for the fragile\nOrgueil matrix without causing disintegration. While we acknowledge the persistent challenge of\ncontamination, this careful curation represents the most robust mitigation strategy for this meteorite\ntype. The homogeneously black, fine-grained matrix showed no visual signs of surface alteration,\nconfirming its interior origin. Notwithstanding, given the long curation of Orgueil, it is well known that\nOrgueil contains some biological contamination. However, we chose Orgueil for the optimization of\nour extraction protocol and data comparison of organic compounds extracted as to date it is one of\nthe CI chondrites best resembling the mineralogy of Ryugu. We included the following modification to\nthe SI material.\nRevised Supplementary Information: “A 178.3 mg fragment of the Orgueil meteorite, allocated by\nthe Muséum National d’Histoire Naturelle (MNHN) in Paris and stored in a plastic container\n(Supplementary Figure 2), was analyzed in this study. This fragment was specifically selected from the\ninterior of a larger stone to minimize potential terrestrial contamination.\nSpecific comments:\nAbstract: The present data set shown in the manuscript does not sufficiently represent the presence of\nextraterrestrial sugars.\nResponse: This has been corrected as suggested.\nThe color code for the sample and procedural blank should be within the same range, from 0 to the\nmaximum, to allow readers to compare them. For example, Fig 1 A and B should be from 0 (blue) to\n300000 (red).\nResponse: We have fixed the z-axis scales for the samples and procedural blanks.\nThe total 2D chromatograms covering all investigated sugars for samples, blanks, and the standard\nshould be shown. The present manuscript contains only Orgueil and its procedural blank (Fig. 4).\nResponse: We now present the full two-dimensional gas chromatograms for sugars detected in\nOrgueil in Fig. 4 and Supplementary Figure 10, along with their respective procedural blanks. In\naddition, we have provided the mass spectral data for the detected sugars in Orgueil as methylboronic\nacid esters, alongside their respective mass spectra in the reference standards and procedural blanks\n(Supplementary Figures 11–14).\nGiven the low quantities of sugars detected in Ryugu, we specifically opted for presenting just the\ndetailed views to best highlight the enantioseparation and contamination, which would be lost in the\noverall 2D chromatograms. Furthermore, a separate manuscript on the development of the protocol\nfor simultaneous analysis of amino acids and sugars, and the impact of the mineral matrix on their\nrecoveries is currently underway.\nL57: Even though there is some potential for the microbial colonization of Ryugu sample, the evidence\nis poor in this cited paper limited in shape, which can be formed by withering. Also, this potential\ncontamination happened in the allocated sample by the researchers which means that the allocated\nsample was not contaminated. The present explanation is confusing.\nResponse: We thank the reviewer for this valuable clarification and fully understand the concern\nregarding the interpretation of the cited study and the phrasing of our original paragraph. Our\nintention was not to suggest widespread contamination or to question the integrity of the Hayabusa2\nor OSIRIS-REx curation procedures, but rather to highlight the broader analytical challenge of\ndistinguishing indigenous organics from possible terrestrial contributions, which remains a key\nconcern for all types of extraterrestrial materials. To avoid confusion and ensure the statement is\naccurate and appropriately cautious, we have revised the paragraph as follows:\nRevised in the manuscript: “A major challenge in analyzing prebiotically relevant organics such as\namino acids and sugars from astrophysical samples lies in confirming their extraterrestrial origin, due\nto the ever-present risk of terrestrial contamination. While meteorites are often subject to terrestrial\nweathering and potential microbial colonization prior to analysis30,31, even returned samples—such as\nthose from (162173) Ryugu and (101955) Bennu—despite being collected under meticulously\ncontrolled conditions by JAXA’s Hayabusa2 and NASA’s OSIRIS-REx missions31–34, require meticulous\nhandling and verification protocols to confidently assess indigenous organics.”\nL102-103: The author explained here that “Key to this methodology is a mild extraction protocol that\nreplaces conventional high-temperature acid hydrolysis with milder ultrasonic-assisted extraction to\nprevent thermal degradation of sugars.” However, this is not correct. The previous sugar extraction\nwas conducted at room temperature with water (Cooper et al., 2001) or 2% HCl, which is lower\nconcentration than amino acid hydrolysis (Furukawa et al., 2019) with sonication. Thus,\nultrasonic-assisted mild extraction is not new.\nResponse: We have rephrased this sentence as follows:\nRevised in the manuscript: “Key to this methodology is a mild extraction protocol employing\nultrasonic-assisted extraction (temperature <20°C, neutral pH, and 10-minute sonication intervals) to\nprevent thermal degradation of sugars.”\nL123: The manuscript describes that “we unambiguously detected both enantiomers of arabinose and\nxylose in Ryugu extracts at concentrations significantly above the procedural blank level.” However,\nthe amounts of arabinose and xylose in the procedural blank are not shown in the manuscript. Figures\n2 and 3 clearly show that there are larger amounts of L-arabinose and D-xylose in the procedural blank\nthan in the Ryugu sample. So, the description in the manuscript is not correct. The 3D peaks of D-\narabinose and L-xylose look larger in Ryugu than the procedural blank, but these peaks in Ryugu are\nmagnified in these figures. So, the figure does not provide information on their amounts.\nIn the revised manuscript, the amounts of both D and L arabinose and xylose in the procedural blank\nshould be shown in Table 1 and explained based on these amounts.\nResponse: As explained in response to your point “1”, we have carried out a thorough study of the\nsources of contamination and we have correspondingly revised the following sections of the\nmanuscript:\nRevised in the manuscript: “Despite the limited sample quantity of 17.5 mg of pristine asteroid\nmaterial and the challenges associated with the extraction and analysis of sugars from extraterrestrial\nmaterial, we unambiguously detected both enantiomers of arabinose and xylose in Ryugu combined\nextracts (A0478 and A0483) in an enantiomeric composition distinct from that of the procedural blank\n(Supplementary Figure 7). If all sugar content in the Ryugu extracts was introduced throughout the\nanalytical procedure, one would expect the enantiomeric composition to closely resemble the one of\nthe procedural blank.”\nRevised in the manuscript: “Xylose enantiomers were also successfully resolved in the Ryugu sample,\nshowing a pronounced predominance of the biological D-enantiomer (Fig. 3A). Unlike for arabinose,\nthe extremely low quantities of xylose in the Ryugu extract do not enable us to unambiguously\ndistinguish its origin when compared to the procedural blanks (Supplementary Figures 7 and 8), which\nmakes its assignment much more elusive. Notwithstanding, the present detection of xylose in the\nRyugu extracts sets a precedent for future studies, where improved extraction efficiency is very likely\nto lead to more conclusive results.”\nRevised in the manuscript: “To better constrain the origin of the detected sugars, we conducted a\ndetailed assessment of potential contamination sources in our procedural blanks. We compared sugar\nlevels in the reagent blank with those in procedural blanks prepared without and with the SiO₂ matrix,\nwhich indicated that the major contribution to contamination arose during the derivatization step,\nspecifically from the derivatization reagents. (Supplementary Note 2, Supplementary Figures 6–8).”\nRevised in the manuscript: \"Importantly, these recovery tests provide the first evidence of sugar-\nspecific interactions with the carbonaceous chondrite matrix, highlighting the need for developing\nstandardized protocols employing closely resembling meteorite matrix in procedural blanks so that a\nblank-correction can be made to accurately quantify absolute extraterrestrial abundances and\nenantiomeric excesses. This is particularly important for drawing comparisons between the organic\ncontent in distinct parent bodies.”\nRevised in the manuscript: “Both were detected in Ryugu aggregates, even though xylose with yet\nelusive origin. Arabinose exhibited significantly distinct enantiomeric composition as opposed to the\nprocedural blank.”\nFurthermore, we now highlight both enantiomers of arabinose and xylose in the procedural blanks in\nFigures 2 and 3, as well as show their respective mass spectra. We also newly added “Supplementary\nNote 2: Assessing the indigenous nature of sugars” to the Supplementary Information file.\nL128: The manuscript explains that arabinose in Ryugu has a D/L approximately 1.0. However, Table 1\nshows that the D/L of arabinose in Ryugu is 0.727. They are not racemic, but D-rich.\nResponse: This sentence has been rephrased as follows:\nRevised in the manuscript: “Resolved D- and L-enantiomers of arabinose in the Ryugu sample show a\nslight excess of the L-form (D/L ≈ 0.67 (Fig. 2A), in contrast to the procedural blank (PB) which showed\na strong predominance of non-biologically less abundant D-arabinose (Fig. 2B, D/L ≈ 2.36).”\nTable 1: The manuscript explains in L 142 that “D-arabinose and L-xylose as ~0.01 nmol/g and ~0.001\nnmol/g, respectively”. These values would not be consistent with the data in Table.\nResponse: The values in Table 1 (1.12 ppb for D-arabinose and 0.18 ppb for L-xylose) are indeed\nconsistent with the stated concentrations of ~0.01 nmol/g and ~0.001 nmol/g in line 142. The\nconversion from mass to molar concentration was performed as follows, using the equivalence 1ppb\n= 1ng/g and a molecular weight of 150.13 g/mol for both pentoses:\nD-arabinose: (1.12 ng/g) / (150.13 g/mol) = 0.0075 nmol/g ≈ 0.01 nmol/g\nL-xylose: (0.18 ng/g) / (150.13 g/mol) = 0.0012 nmol/g ≈ 0.001 nmol/g\nL145-146: The manuscript discusses that the lower abundance of contaminants in Ryugu than PB was\ncaused by the adsorption by minerals. In this case, what was the source of the contamination? Did the\nauthors analyze solvents every time before the analysis of the sample and PB? If so, please describe\nthis to eliminate the possibility of cross-contamination in GC-MS. Otherwise, the cross-contamination\nmay explain the chromatogram of Ryugu (real Ryugu+PB) or (PB+standard). The PB of Orgueil shown\nin Fig. 4 shows that D- and L-lyxose and D- and L-ribose are contaminated. D- and L-lyxose are\nrare sugars and L-ribose is non-biological sugar. Thus, they could not be biological contaminations. So, they\ncould be contaminated from the standard chemical mixture in the GC-MS. If this happened in the Ryugu\nsample. The presence of L-xylose and D-arabinose could be explained by this effect. The authors should\nshow the analytical blank before the Ryugu analysis.\nResponse: As detailed above, we have performed a detailed study of the sources of sugar\ncontamination and revised the corresponding parts of the manuscript.\nL167: The chromatograms of ribulose should be shown in the manuscript.\nL167: The author should show chromatograms of Orgueil, procedural blank, and the standard of\nribulose.\nResponse: We appreciate the reviewer’s careful attention to this important point, and we have now\nincluded the missing ribulose data to strengthen the evidence supporting its detection. We have now\nincluded the chromatograms for ribulose in the Orgueil meteorite sample and the corresponding\nreference standard in Figure 4 (revised manuscript). Additionally, the comparison of the ribulose\nenantiomers across the procedural blanks ±SiO has been added to the Supplementary Information\n2\n(Supplementary Figure S10) to confirm its identification. These updates ensure full transparency and\nsupport the validity of our detection.\nL172-175: The author discussed that acid extraction of sugars from Murchison reported in Furukawa\net al. (2019) may introduce sugar contamination and promote sugar formation reaction. However, in\nthe previous study, the paper described no detectable pentose contamination in the procedural blank.\nThus, the contamination from 2% HCl in the extraction is unfounded. Further, sugar formation by the\nformose reaction is highly sensitive to high pH, indicating that low pH is more suitable for\nextraction. The higher stabilities of sugars at lower pH are also evident in other previous study, in which the\ndegradation of ribose is 100 times lower at pH4.5 compared to 6.5 (Larralde et al., 1995).\nThus, this discussion should be removed.\nResponse: Thank you very much for this valuable explanation and clarification. We acknowledge the\nreviewer’s point regarding the absence of detectable pentose contamination in the procedural blank,\nthe low likelihood of formose-type sugar formation under acidic conditions, and the improved stability\nof sugars at lower pH. In light of this, we have removed the discussion previously included in lines\n172–175 as suggested.\nL244-245: Arabinose in Ryugu is enriched in L-form.\nResponse: This information is not included in lines L244–245, but we have rephrased the sentence in\nlines L127–129 as follows:\nRevised in the manuscript: “Resolved D- and L-enantiomers of arabinose in the Ryugu sample show a\nslight excess of the L-form (D/L ≈ 0.67 (Fig. 2A), in contrast to the procedural blank (PB) which showed\na strong predominance of non-biologically less abundant D-arabinose (Fig. 2B, D/L ≈ 2.36).”\nL293: The author discussed that abundant ammonia stabilized sugars, by maintaining pH for optimal\naldol condensation. However, this is not correct. Ammonia react with sugars to form may by-products\n(e.g., Kebukawa et al., Science Advances 2017). Further, aldol condensation promoted by high pH\nconsume sugars as shown in many previous studies including the author’s work (Vinogradoff et al.,\n2024).\nResponse: We thank the reviewer for raising this important point. Our intention was not to suggest\nthat high global ammonia concentrations were conducive to sugar stability, but rather to propose a\nmore nuanced role where ammonia is not necessarily limited to a single pathway. Although it is true\nthat excess NH₃ can promote nitrogen incorporation into organic compounds, potentially competing\nwith sugar formation or participate in sugar degradation through hydrolysis (retro-aldol reactions), it\ncan also act as a crucial catalyst for aldol condensations, favoring formaldehyde polymerization into\nsugars, or even as a radical scavenger that protects sugars from degradation by reactive oxygen species\nor other radicals. To clarify these competing mechanisms, the updated paragraph now reads:\nRevised in the manuscript: “Indeed, both Ryugu and Orgueil show mineralogical evidence of extensive\nlow-temperature aqueous alteration, including phyllosilicates, carbonates, and ammonium\nreservoirs17,60,61, consistent with mildly alkaline aqueous alteration (pH ~8–9)13,51 at temperatures\nbelow 150 °C. The formation and preservation of sugars on these parent bodies were likely shaped by\nthe same mineralogical and alteration context. Although alkaline conditions can channel sugar\nprecursors into degradation pathways, such as Maillard-type reactions that consume both amino acids\nand sugars (Garcia et al. ACS Earth and Space Chemistry 8, 2024), they are also essential for sugar\nsynthesis. This interplay encompasses: (1) formose-type reactions catalyzed on phyllosilicate surfaces\nin fluids enriched in Mg2+, Ca2+, and Fe2+ ions63,64; (2) base-catalyzed polymerization of interstellar\naldehydes such as formaldehyde and glycolaldehyde23,24; and (3) stabilization via adsorption onto\nmineral surfaces or trapping within phyllosilicate interlayers (Viennet et al. Geophysical Perspective\nLetters 25, 2023) which can mitigate degradation).”\n-6: Do the 2D and 3D chromatograms show total ion chromatograms or selected ion chromatograms?\nThis should be explained in the caption with m/z range or m/z values.\nResponse: We thank the reviewer for highlighting this important clarification. The 2D and 3D\nchromatograms represent selected ion chromatograms corresponding to specific m/z signals of\ninterest, rather than total ion chromatograms. We have updated the figure captions of Figs. 2–4 to\nexplicitly state the m/z values displayed in each of them, ensuring full transparency in data\nrepresentation.\nRevised in the manuscript:\n“Figure 2. Arabinose detection in asteroid Ryugu. Enantioselective GC×GC–TOF-MS selected ion\nchromatograms (m/z = 84) and mass spectra of arabinose enantiomers as methylboronic acid esters\ndetected in (A) the Ryugu asteroid sample compared to (B) a SiO procedural blank processed\n2\nidentically (SiO -PB) and (C) a reference standard (RS).\nchromatograms (m/z = 97) and mass spectra of xylose enantiomers as methylboronic acid esters\ndetected in (A) the Ryugu asteroid sample compared to (B) a SiO procedural blank processed\n2\nidentically (SiO -PB) and (C) a reference standard (RS).\n(m/z = 84 and 97) chromatograms of C5 sugar enantiomers as methylboronic acid esters detected in\n(A) the Orgueil meteorite sample compared to (B) the reference standard (RS).”\nFigure 4 and 5: The assignment of D-arabinose is different between Figure 4 and 5.\nResponse: Thank you for spotting the incorrect assignment of D-arabinose in Fig. 4. We have corrected\nFig. 4 while Fig. 5 has been removed from the manuscript.\nMinor comments:\nL28: Proteins are better described as catalytic biopolymers rather than informational biopolymers,\nsince the term informational biopolymers is widely used to express the biopolymers that have gene\ninformation.\nResponse: The term “informational” originally refers to nucleic acids, while adding “catalytic” would\nspecifically apply to proteins. To avoid both inaccuracy and an overly long sentence that would require\ndetailing the roles of each biopolymer (RNA/DNA and proteins), we chose to remove the adjective\naltogether and simply refer to fundamental biopolymers.\nL80-97: These paragraphs mostly describe results and implications. Thus, they should be merged in the\nfollowing section.\nResponse: We would like to keep these paragraphs at the end of the Introduction section as a brief\nsummary of the key outcomes of the present study.\nL82: ribuloses to ribulose\nResponse: This has been corrected as suggested.\nL98: The title of this section should be “Results and Discussion”\nResponse: We tend to disagree with the reviewer on this point as we would like to keep two separate\nsections, i.e. “Results”, where we present the outcomes of our gas chromatography analyses, and\n“Discussion”, where we discuss the significance and implications of the results in the light of\nextraterrestrial synthesis of sugars and their potential contribution to prebiotic chemistry, while\nhighlighting the limitations of current extraction protocols.\nL118: “as well as the the C5 ketose” to “as well as the C5 ketose”\nResponse: This has been corrected as suggested.\nL155: (PB) to (B)\nResponse: Thank you for pointing this out. We have modified the text to read:\nRevised in the manuscript: “…compared to (B) a SiO procedural blank (SiO -PB) processed under\n2 2\nidentical conditions.”\nReviewer #3 (Remarks to the Author):\nHere are my comments on the revised manuscript NCOMMS-25-43746 entitled “Abiotic sugars in\n(162173) Ryugu and the primitive CI carbonaceous chondrite Orgueil” resubmitted to Nature\nCommunications.\nFirst, I would like to apologize for my late reply due to a quite unique situation that was outside of my\ncontrol. Second, I would like to thank the authors for taking the time to thoroughly address all my\ncomments as well as all the comments from the other two reviewers.\nDespite of all the justified explanations and subsequent significant changes made to the revised\nversion of the manuscript, I still can’t recommend this manuscript for publication in Nature\nCommunications. Below I provide a more detail argumentation that led to my decision. That being\nsaid, this doesn’t mean that I don’t recommend this manuscript for publication at all. The work\npresented here is important and show novel results that deserve to be published (in a different\njournal) and shared with the scientific community.\nI totally understand the arguments presented by the authors to defend the data reported in the\nmanuscript, and I fully appreciate the difficulty to obtain these data given the limited quantities of\nmaterials they had to work with. On the other hand, the long replies from the authors to the\ncomments of all three reviewers all seem to point towards the fact that, given the data collected for\nthe sample of Ryugu that was analyzed in this study, given the low recovery rate for the extraction of\nsugars from the mineral matrix, and given the analytical protocol resulting in the contamination of\nthe samples, and consequently the results presented in the manuscript, there is currently no way to\nknow for sure that the sugars identified in the chromatograms of this Ryugu sample are indigenous to\nRyugu.\nI understand that the data collected for amino acids as well as the distribution of sugars in the\nsamples compared with the procedural blank (PB) data suggest an indigenous origin from Ryugu,\nbecause their enantiomeric distributions are different from that of the PBs, but they don’t provide a\ndefinitive proof. In particular, the fact that quantitative amounts and enantiomeric excess\nmeasurements can’t be corrected using the PBs makes the detection of both amino acids and sugars\ninconclusive. Believe me, I really want these compounds to be indigenous to Ryugu, and I think their\nunambiguous presence would be a great result, but the data shown in the manuscript are currently\ninsufficient to unambiguously confirm these detections. I understand that the detection of amino\nacids in Ryugu in the present study supports an extraterrestrial origin for these compounds. However,\nas the authors explicitly admit in their replies at multiple occasions as well as in the revisions to the\nmanuscript, these values are only estimates because they can’t be blank-corrected. This comment\nincludes the values for the abundances and enantiomeric excesses for both amino acids and sugars. In\naddition, since the extraction protocols are different for amino acids and sugars, even if amino acids\nare indigenous to Ryugu, this doesn’t mean that sugars are, because different extraction solvents can\ncontain different levels of amino acid and sugar contaminants.\nTherefore, I don’t think the data and results presented in this manuscript are strong enough to\nconvince everybody that sugars were detected in Ryugu without any possible doubt, and I believe that\npublications in Nature Communications should show results that are proof-tight and totally\nunambiguous, which is not the case here.\nNow, as I mentioned above, I am convinced that the results presented in this manuscript are\nimportant and they should be published. Given that in their responses to the reviewers, the authors\nmentioned at multiple occasions that they are currently working on a separate manuscript in which\nthey will address the development of the protocol for the simultaneous analysis of amino acids and\nsugars, as well as the impact of the mineral matrix on their recoveries, I suggest that the authors\ncombine the discussion they are planning to address in that other paper with the results presented in\nthe manuscript submitted to Nature Communications to write a full paper that includes the results for\namino acids and sugars, their extraction protocol, the impact of the mineral matrix, and a more\ncomprehensive discussion of the interpretation of these results after addressing the contamination\nissue from the PBs and the effect of the mineral matrix for the extraction of amino acids and sugars.\nThat new paper would obviously be much longer and more detailed, and therefore probably wouldn’t\nfit in the format for publication in Nature Communications. However, I believe it would present better,\nstronger arguments for the origin of the amino acids and sugars detected in the Ryugu sample\nstudied here, even if quantitative results can’t be taken with certainty, and it would still be a\nsignificant contribution to the scientific community.\nResponse: Given the significant concern regarding potential contamination of the Ryugu samples, we\nhave removed all associated data from the manuscript.\nOther comments:\nTitle: In their response to my comment regarding the use of “primitive” in the title, the authors said\nthat had deleted the word from the title. However, in the revised version that was sent to me, the\nword “primitive” is still in the title of the manuscript.\nResponse: The final suggestion for the title of our revised manuscript is: “Abiotic sugar enantiomers\nin the CI carbonaceous chondrite Orgueil”\nLines 9-10 & 263: The first sentence doesn’t make much sense. I understand that the authors want to\npoint out that it’s more difficult to detect sugars than amino acids and nucleobases in extraterrestrial\nmaterials, but there must be a better way to do so, for example, by just saying that organic\ncompounds, including compounds of prebiotic interest, have been detected in extraterrestrial\nmaterials, however, the detection of sugars appears to be more analytically challenging that the\ndetection of other prebiotic compounds such as amino acids and nucleobases. Also, labeling\nmeteoritic amino acids, nucleobases, and sugars as prebiotic compounds is, to my opinion, not\nentirely justified. Indeed, we know is that several amino acids, nucleobases, and sugars are used in\nmodern biology, we know that some of them are also detected in meteorites. But we don’t know\nwhich compounds were used in the prebiotic processes that led to the first biological reactions. Maybe those\nmeteoritic organics were significantly involved in the emergence of life, maybe not. Maybe life emerged from reactions\nbetween other organic compounds which, at a later stage in life’s evolution, were then replaced with the amino acids,\nnucleobases, and sugars that biology uses today.\nResponse: Thank you very much for your thoughtful reflection on the opening sentence of our\nabstract; we understand and appreciate your reasoning. However, the abstract is too short to address\nall these considerations at once and is meant primarily to introduce our study, which indeed focuses\non the current discrepancy between the detection of sugars and that of other biological molecules\nsuch as amino acids and nucleobases.\nWhether these extraterrestrial molecules were required for the origins of life remains uncertain.\nNevertheless, their distribution in Solar System bodies and on planetary surfaces provides valuable\ninformation about chemical pathways and evolution. For this reason, we deliberately avoid referring\nto them as prebiotic molecules in the abstract. Instead, we highlight their interstellar and Solar System\nchemistry as a whole to inform our understanding of these pathways. Only at the end do we mention\ntheir potential link to prebiotic chemistry. We believe that our abstract does not overstate the role of\namino acids, nucleobases, and sugars; rather, elucidating their formation pathways under\nastrophysical conditions is, in itself, a significant scientific contribution.\nLine 12 & 44-45: Although many people seem to believe so, glycolaldehyde (misspelled on line 44) is\nnot the simplest sugar. The simplest sugars contain 3 carbon atoms and are glyceraldehyde (aldose)\nand dihydroxyacetone (ketose), the same way many people believe that carbamic acid is the simplest\namino acid (it’s incorrect), and urea and formamide are the smallest compounds with peptide bonds\n(also incorrect).\nResponse: We fully agree that glycolaldehyde is not the smallest sugar molecule, and we have revised\nthe manuscript accordingly. All references to glycolaldehyde as a sugar molecule have been removed\nor rephrased where necessary.\nLine 20: As mentioned correctly here in this sentence, the fact that the sugars detected in the Ryugu\nsample exhibit distinct enantiomeric distributions compared to PBs only suggests an extraterrestrial\norigin for these compounds, but it doesn’t confirm that these compounds are indigenous to Ryugu,\ngiven the high levels of contamination in the PBs and the impossibility to blank-correct the\nabundances and enantiomeric excesses with the data presented here.\nResponse: Given the significant concern regarding potential contamination of the Ryugu samples, we\nhave removed all associated data from the manuscript.\nLine 20-21 & later again in the main body of the manuscript: Is there a way to extrapolate the actual\nabundances of sugars in extraterrestrial materials knowing that their recovery rates are “often below\n5%”? If the other manuscript the authors are working on can explain why and explicitly estimate by\nhow much the detection of sugars in extraterrestrial materials is typically underestimated, that would\nbe great information for future studies.\nResponse: Thank you very much for your comment. Our goal is to obtain statistically proven recovery\nrates for our methodology, so that we can approach the true abundances of both amino acids and\nsugar molecules. In the absence of such recovery rates, the abundances of extraterrestrial molecules\nreported so far should be considered lower estimates—an issue we believe represents a fundamental\nproblem within the meteoritic community and one that is not resolved simply by providing blank-\ncorrected values. However, as noted, this part of the discussion will need to be addressed in detail in\nour forthcoming methodology manuscript.\nLines 39-41, 53-55, & 331-339: Following one of the points I made in my first review and the response\nfrom the authors, the detection of sugar derivatives in meteorites and other extraterrestrial materials\nshouldn’t be restricted to the detection of sugars only. If we consider sugar acids and sugar alcohols\nas compounds that are present in extraterrestrial materials and have the potential to be converted\ninto sugars through processes at the Earth’s surface or in Earth’s oceans, then Furukawa et al. (2019)\nis not the only paper reporting the detection of sugar derivatives in meteorites, as Cooper et al. (2001)\n[Ref. 32 in the manuscript], Cooper & Rios (2016) [Ref. 61 in the manuscript], and Nuevo et al. (2018)\n[Ref. 20 in the manuscript] collectively reported the detection of several sugar alcohols, sugars acids,\nsugar diacids, deoxysugar acids, and deoxysugar alcohols in meteorites with up to 6 carbon atoms.\nGiven the detection of all these sugar derivatives in meteorites, would it be possible that the reason\nwhy sugars themselves are more difficult to detect is because in meteorites (and maybe other\nextraterrestrial materials) sugar derivatives are predominantly present in their acid and/or alcohol\nforms rather than their pure sugar forms? That’s somehow what the authors say on lines 53-55,\nalthough the sentence in the manuscript seems to imply that sugars are unstable and are converted\ninto sugar acids and alcohols, instead of saying that maybe sugar acids and alcohols are easier to\nform than their sugar counterparts, hence resulting in the detection of smaller amounts of sugars\ncompared with sugar acids and alcohols.\nResponse: In the absence of reliable abundance data for sugar molecules (aldoses/ketoses) in\nmeteorite samples—as well as for sugar acids and sugar alcohols—due to the lack of recovery rates,\nthe limited amount of data available, and the previous use of reduction/oxidation steps that only target\nthe sum of sugar alcohols/acids, it is currently impossible to draw firm conclusions about their true\ndistribution.\nCiting the study by Furukawa et al. (2019) as the only work reporting individual sugar molecules reflects\nthe current state of the scientific literature. This in no way minimizes the important detection of sugar\nderivatives by Cooper and colleagues; rather, it simply acknowledges the information available to date.\nAt present, it would be speculative to discuss why only a few studies report on sugars. From our own\nexperience, there are indeed several challenges associated with extracting and detecting sugars in\nextraterrestrial material. Nevertheless, these difficulties may not be universal, and it would be\ninappropriate to extrapolate our experience to the motivations of other researchers or to the broader\nlimitations of current data. However, once optimized and validated recovery rates are established,\nour goal is to address the current lack of data on the distribution of sugar molecules across different\ncarbonaceous chondrites.\nLines 90-91: Here I would suggest to use the same phrasing as on Line 20, i.e., by saying that the distinct\nenantiomeric distributions of the detected sugars compared with the PBs suggest an extraterrestrial\norigin, rather than “support a potentially extraterrestrial origin”.\nResponse: Given the significant concern regarding potential contamination of the Ryugu samples, we\nhave removed all associated data from the manuscript.\nLines 123-124: Cooper & Rios is not Ref. 32. Cooper & Rios (2016) is Ref. 61, while Ref. 32 is Cooper et\nal. (2001). Also, contrary to what is said in this sentence, Cooper et al. (2001) and Cooper & Rios (2016)\ndidn’t report the detection of C3-C5 sugar aldoses. Rather, Cooper et al. (2001) reported the detection\nof only one sugar (C3 dihydroxyacetone) as well as several C3-C6 sugar alcohols, acids, diacids, and\ndeoxysugar acids in meteorites, while Cooper & Rios (2016) focused on the study of meteoritic sugar\nacids and their enantiomeric excesses.\nResponse: Thank you for your careful review. We have updated the main text to reference Cooper et\nal. (2001) (ref 33) instead of Cooper & Rios (2016). We would like to clarify for the reviewer that our\nstudy does not claim that Cooper et al. detected C3 to C5 sugar aldoses. Rather, we noted the reported\ndecline in their sugar-related molecules distribution (see extract from Cooper et al. below), which\ninformed our decision to focus on C3–C5 sugar aldoses in our own study. We anticipated these would\nbe present in the highest—and thus detectable—quantities.\nCooper et al (2001): “….Our analyses of several Murchison extracts, and a Murray extract, show a\nvariety of water-soluble polyols (Fig. 1). The compounds that we identified include a sugar,\ndihydroxyacetone (sugars by definition are polyhydroxy aldehydes or ketones); sugar alcohols; sugar\nmono-acids; sugar di-acids; and deoxysugar acids (or ‘saccharinic’ acids). In general, the compounds\nfollow the abiotic synthesis pattern of other meteorite classes of organic compounds1: a general\ndecrease in abundance with increasing carbon number within a class of compounds, and many, if not\nall, possible isomers present at a given carbon number.”\nLines 129-130, Supplementary Figure 8, and most of the discussion up to line 173: In this revised version\nof the manuscript, as well as in the responses of the authors to the reviewers’ comments,\nSupplementary Figure 8 seems central to the argument that the distinct enantiomeric compositions of\nthe sugars detected in, on the one hand, Orgueil and Ryugu, and, on the other hand, the PBs justify the\nsuggestion that the sugars detected in those samples are of extraterrestrial origin. Yet, this important\nfigure can only be found in the Supplementary Information.\nResponse: : Given the significant concern regarding potential contamination of the Ryugu samples, we\nhave removed all associated data from the manuscript including in depth discussion on the distinct ee.\nTables 1-3: As mentioned and argued multiple times in the first round of reviews and the authors’\nresponses to the reviewers’ comments, the absolute values for abundances and the enantiomeric\nexcesses derived from these values don’t make much sense if they can’t be blank-corrected. Injecting\nseveral times a sample that is contaminated will result in narrowing the error bars on the\nmeasurements, but it won’t mask the fact that all those injections contain contaminants that\nsignificantly contribute to the derived abundances. Maybe the discussion and conclusions of the other\nmanuscript that the authors are currently writing (and that I recommend to combine with the present\nmanuscript) will strengthen the conclusion that the sugars and amino acids and sugars detected in Ryugu are of\nextraterrestrial origin, but as presented in the current version of the manuscript, this conclusion is too\nfar-fetched and, to my opinion, the enantiomeric excesses reported in Tables 1-3 don’t support any of\nthe conclusions of the manuscript.\nResponse: Thank you for your comment. We provide both raw data and blank-corrected data in Tables\n1–3 in order to address your concern and the suggestions made by the other reviewers.\nReviewer #1 (Remarks to the Author):\nReview comments on the manuscript #NCOMMS-25-43746B by Meinert et al.\nOverall:\nThis manuscript initially reported the detection of sugars in samples returned from the asteroid Ryugu\nas well as in the Orgueil meteorite. After several rounds of review, however, the authors chose to focus\non the findings from Orgueil. Because the concentration of sugars detected in Orgueil is substantially\nhigher than that in the blank samples, there is little doubt that these sugars are largely indigenous to\nthe meteorite. The authors further argue that the lower number of sugar detections in meteoritic\nsamples in previous studies is due to the reduced recovery from the samples. This explanation may be\npartly valid. Nevertheless, the central contribution of this work lies in demonstrating the presence of\nindigenous sugars in Orgueil; the technical aspects are secondary. The scarcity of previous publications\non meteoritic sugars is of limited relevance to readers. Therefore, I recommend that the authors\nemphasize the significance of their findings more prominently and consider removing, at least in part,\nclaims related to technical issues from the main text. Also, as long as the indigeneity of sugars in Orgueil\nis guaranteed to some extent, the results and discussion on the detection of chiral amino acids may not\nbe necessary so much; these may be moved to the Supplementary Information. Instead, the detection\nof the indigenous sugars, as well as their potential importance, their formation mechanisms, and\ncomparison with other meteorites/asteroids, should be discussed much more.\nI believe the content of the current version itself could merit publication in Nature Communications,\ntaking into account the above and the following concerns. Please accept my apologies that some of the\nquestions and opinions below may not have been communicated to the authors in earlier rounds of\nreview, which primarily focused on the justification of the Ryugu results.\n1. L38, “only a single study by Furukawa et al. has confirmed that...”: Very recently, as the authors may\nhave already known, a paper on the detection of sugars in the sample returned from the asteroid Bennu\nhas been published (Furukawa et al. 2025, Nature Geoscience, doi:10.1038/s41561-025-01838-6).\nAlthough that paper was published after the submission of the current manuscript, I believe this\nsentence should be revised for clarity. Furthermore, given that asteroid Bennu is considered to exhibit\nCI-like characteristics, a comparison of sugar distributions between Orgueil and Bennu in the Discussion\nsection would significantly strengthen the manuscript.\nResponse: We thank the reviewer for highlighting this recent publication. Indeed, we are aware of the\nstudy reporting the detection of sugars in samples returned from asteroid Bennu (Furukawa et al.,\n2025, Nature Geoscience), and we have now cited this work in the revised manuscript. We have\nupdated several paragraphs to reflect these findings and incorporated the quantitative results of the\naldopentoses detected in Bennu into Table 1, allowing a more direct comparison with our data from\nOrgueil. This addition also enables a discussion of similarities and differences in sugar distributions\nbetween Orgueil and Bennu, strengthening indeed the context and implications of our study.\n2. L97: What is the discrepancy with earlier studies?\nResponse: In response to the comment, this sentence has been removed from the manuscript.\n3. Figure 1: On the right side of the figure, it looks like the sugar fraction is eluted with H2O and MeOH.\nIt is also mentioned in the Method section. While in Supplementary Figure 3, it is mentioned that the\nmethanol extract is eluted with 5x1 mL H2O. Please clarify which is correct.\nResponse: We thank the reviewer for this comment. We have corrected Figure 1 and Supplementary\nFigure 3 to clarify the elution conditions. The sugar fraction was eluted using 5 × 0.5 mL of H₂O.\n4. Figure 2: Please show the corresponding blank chromatogram in this figure. Since the names of\ncompounds are shown in the sample chromatogram, no need to show the standards chromatogram in\nthe main text (this may be fine to appear in SI, instead).\nResponse: We thank the reviewer for the suggestion. The comparison with the standard is included to\ndemonstrate the quality of sugar identification based on the selected ions (m/z = 84 and 97). We\ntherefore prefer to keep the standard chromatogram in Figure 2, as it provides clear evidence\nsupporting the identity of the sugars detected in Orgueil, based on two-dimensional retention times\nand corresponding mass spectra shown in Supplementary Figure 6.\n5. L145: How rapidly do the sugar derivatives decompose? This information may be of value to readers.\nResponse: As shown in Supplementary Figure 10, the degradation of sugar derivatives is observable\nbetween individual injections, each with a runtime of approximately 1 hour. To maintain readability\nfor the broad audience of Nature Communications, we have chosen not to include further\nmethodological details in the main text. We note that a more technical investigation of aldopentose\nrecovery and degradation kinetics under our analytical conditions is ongoing and will be reported\nseparately.\n6. L180-: What kind of “sugar-specific” interactions did the authors find? Please clarify.\nWithout any clear data, the words “first evidence” should be too strong.\nResponse: We thank the reviewer for this important comment. By “sugar-specific interactions,” we\nrefer to the distinct and reproducible differences observed among individual aldopentoses in both\nrecovery efficiencies and degradation behavior under identical experimental conditions. As shown in\nTable 1, the measured recovery rates differ significantly between ribose, arabinose, xylose, and lyxose,\nindicating that these structurally similar sugars do not interact uniformly with the sample matrix\nand/or extraction protocol. In addition, Supplementary Fig. 10 demonstrates sugar-dependent\ndegradation patterns, with individual aldopentoses exhibiting markedly different stability profiles\nduring analysis. Taken together, these observations provide direct experimental evidence for\ndifferential, sugar-specific interactions with the mineral matrix and/or during analytical handling,\nrather than uniform behavior across all aldopentoses. To avoid overstatement, we have revised the\nmanuscript to replace the term “first evidence” with “evidence” and have clarified that our findings\nrepresent experimental indications of sugar-dependent behavior under the conditions investigated,\nrather than a comprehensive mechanistic description.\n7. L183: I do not understand why the authors insist on reporting the “absolute concentration” of sugars\nin meteorites. Since the recovery test conducted in this study may not accurately reproduce the spatial\ndistribution of sugars within meteorites (e.g., those trapped in minerals), even if recovery rates were\ndetermined for each sugar, these values cannot be readily applied to derive absolute concentrations.\nTherefore, the authors need not emphasize “absolute” concentrations, which cannot be obtained\nwithout certain assumptions.\nResponse: We thank the reviewer for this comment. In response, we have rephrased the relevant\nparagraphs in the Results and Discussion sections and removed references to “absolute”\nconcentrations to better reflect the limitations of our quantitative estimates.\n8. L194 “...proteinogenic, rare, and non-biological types”: What is the difference between “rare” and\n“non-biological” types? It may be fine to show that “...proteionogenic and non-biological types were...”\nResponse: In this context, we prefer to retain the three categories, as they represent a clear scientific\ndistinction in terms of biological relevance and therefore help to distinguish potential sources of\ncontamination. Proteinogenic amino acids are those directly encoded by the genetic code and\nincorporated into proteins by ribosomal translation in extant biology. Rare (non-proteinogenic but\nbiological) amino acids are compounds that occur naturally in terrestrial biological systems but are\nnot encoded by the standard genetic code. These include amino acids found in specialized metabolic\npathways, secondary metabolites, or post-translational modifications (e.g., β-alanine, γ-aminobutyric\nacid). Non-biological amino acids are those not known to be synthesized or utilized by biological\nsystems and are typically associated with abiotic or synthetic formation pathways (e.g., 2,4-DAB). Thus,\nthe term “rare” implies limited or specialized biological occurrence, distinguishing these amino acids\nfrom both proteinogenic species and those with no known biological role.\n9. L275: As noted above, the authors do not need to emphasize “absolute” concentrations, as these\ncannot be easily determined even with recovery tests. While achieving higher recovery is certainly\npreferable to lower recovery, such discussion remains of limited value as long as a high-recovery\nmethod has not yet been established.\nResponse: Please refer to our response to point #7.\n10. L284: If the recovery of sugars from meteorites is potentially low, the role of sugars in meteorites\nfor prebiotic chemistry on the early Earth may not be significant since they cannot be easily released\nfrom meteorites in that environment. Any comments on this point?\nResponse: In our study, the low recovery of sugars primarily reflects the limitations of the extraction\nprotocol we used—particularly the use of methanol as the extraction solvent. Based on our recovery\nexperiments, we consider it likely that the actual sugar abundances in meteorites are higher and\npotentially comparable to those of other soluble organic compounds reported in carbonaceous\nchondrites. Our current data point strongly in this direction, but we prefer to substantiate this\ninterpretation through ongoing follow-up studies that will include expanded recovery tests and\nimproved extraction strategies.\nImportantly, alternative extraction solvents—especially water, which is highly relevant to early Earth\nenvironments—are expected to yield significantly higher sugar recoveries. Such solvents may mobilize\nsugars more efficiently than methanol under geochemical conditions consistent with aqueous\nalteration or weathering on the early Earth. For these reasons, we do not believe that the low recovery\nobserved under our current laboratory protocol necessarily implies low bioavailability of meteoritic\nsugars on the early Earth.\nChanges made to the discussion section: “Our data, together with the recovery experiments presented\nhere, point strongly toward extraction inefficiencies rather than intrinsic rarity as the primary cause of\nthe apparent scarcity of meteoritic sugars. Methanol, the solvent used in this study, extracts sugars\npoorly, and ongoing tests indicate that alternative solvents such as water, which is relevant to early\nEarth environments, substantially improve recovery. Thus, the low yields reported here should not be\ntaken as evidence that sugars were unavailable for prebiotic chemistry. These findings highlight the\nneed for improved extraction protocols and systematic recovery studies using representative matrices\nto more accurately constrain the true abundance and mobility of meteoritic sugars. We briefly note\nthese limitations in the present work, and detailed experimental validation addressing these gaps is\nunderway.”\n11. Tables: Concentrations of sugars and amino acids before blank corrections are not necessary.\nResponse: Given the uncertainties in current methodologies for accurately quantifying\ncontamination—and its clear presence and variability in our samples—we believe it is important to\npresent both the raw (pre–blank-corrected) and the blank-corrected abundances. Showing both sets\nof values provides full transparency regarding the magnitude of contamination, particularly for amino\nacids and sugars of clear biological origin, and allows readers to assess how the correction affects the\nfinal results.\nBecause sugar and amino-acid analyses in meteorite matrices remain analytically challenging, and\ncontamination is both sample-dependent and protocol-dependent, reporting only the corrected values\ncould inadvertently mask the true extent of background contributions. Presenting both therefore gives\na more complete and honest picture of the data quality and the limitations inherent to the current\nstate of the field and our protocol in particular.\n12. Supplementary Information, Top page: The numbers “2” in L15, “4” in L19, etc., may be the\ncorresponding page numbers for the subsection. But it is ambiguous for readers. How about adding the\nsubsection title and aligning the page number on the right side of the page?\nResponse: There was an issue when converting the .doc file to .pdf, which caused the original page\nnumbers to be lost. In the current version, each subsection in the table of contents is followed by its\ncorrect corresponding page number.\n13. Supplementary Figure 5A: The name “MeOH PB” may be replaced with “PB without SiO2” or\nsomething equivalent.\nResponse: That is an excellent idea. We have changed the legends to “PB – without SiO ” and “PB –\n2\nwith SiO ”\n2\n14. Supplementary Figure 6: The mass spectra of L-lyxose look different from that of D-lyxose in terms\nof the relative peak intensity (e.g. m/z 97 and 113). Are they correct?\nResponse: Yes, the spectra shown are the baseline-corrected mass spectra of L- and D-lyxose in the\nanalyzed Orgueil extract. The variability in relative fragment intensities (e.g., at m/z 97 and 113) is\narising from a combination of factors, including the very low quantities of material injected and matrix-\nrelated effects during derivatization and analysis. These influences can cause minor fluctuations in\nionization and fragmentation efficiency between runs, even for enantiomers of the same compound.\nImportantly, the fragmentation patterns themselves are consistent with those expected for lyxose as\nwell as the retention times, so that the observed differences do not affect the identification of either\nenantiomer.\nReviewer #2 (Remarks to the Author):\nThe quality of the manuscript has been improved significantly by this revision. I have only a few\ncomments to improve.\nThe most questionable result remaining in this study is the high abundance of ribose and lyxose, with\nlower abundances of arabinose and xylose. The author replied in the rebuttal letter that they are\ncurrently unable to offer a scientific explanation for the quantitative results, and that this may be due\nto limitations in the analytical protocol. Since this is significantly opposite to all related previous studies,\nthis discrepancy and the possible reason related to the limitations of the analysis should be mentioned\nin the revised manuscript. Otherwise, follow-up studies would have problems with this discrepancy.\nResponse: We believe we have clearly stated that our current recovery rates for sugars are low and\nthat the absolute quantities reported should therefore be regarded as minimum estimates (L243–246).\nWe would also like to be cautious about the assertion that our results are “opposite” to previous\nstudies. To date, the detection of sugars in meteorites has been reported only once in the literature\nby Furukawa et al. (2019) and, more recently, in a sample from Bennu by Furukawa et al. (2025).\nTo the best of our knowledge, our study provides the first recovery-rate assessment for sugars\nextracted from meteorite material. These experiments show that the recovery rates for sugars are\ncurrently not satisfactory, whereas those for amino acids are reasonable within our protocol. Although\nother extraction protocols used in previous studies may indeed yield higher sugar extraction\nefficiencies, it remains premature to draw quantitative comparisons in the absence of published\nrecovery-rate data for sugars in meteorite matrices.\nAs noted in our previous exchange and in the revised manuscript, we are currently conducting\nsystematic evaluations of sugar recovery using multiple extraction strategies. This includes\ninvestigating how the mineral matrix may differentially retain sugars compared to amino acids. Until\nthese controlled recovery-rate data are available, we prefer not to speculate on the origin of the\nobserved quantitative discrepancies. We have explicitly acknowledged this limitation and its\nimplications in the revised manuscript (L180-185; L267-277).\nL18: “the ketopentose” to “a ketopentose”\nResponse: corrected as suggested.\nFigs: Do the numbers on the horizontal axis, like 17:50, mean 17.5 minutes or 17 minutes and 50\nseconds?\nIf they mean latter, they should be in the unit of minutes. If they mean former, this should be shown as\n17.5 min.\nResponse: We have updated all figures and standardized the retention-time units for the first\ndimension to minutes. For example, values such as 17:50 [min:sec] have been converted to 17.8 min,\netc.\nL180: This sentence is still discussing the Ryugu sample.\nResponse: Thank you. We have removed all discussion related to Ryugu."}]

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