Compound‐specific carbon isotope compositions of aldehydes and ketones in the Murchison meteorite
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Bibliographic record
Abstract
Abstract Compound‐specific carbon isotope analysis (δ 13 C) of meteoritic organic compounds can be used to elucidate the abiotic chemical reactions involved in their synthesis. The soluble organic content of the Murchison carbonaceous chondrite has been extensively investigated over the years, with a focus on the origins of amino acids and the potential role of Strecker‐cyanohydrin synthesis in the early solar system. Previous δ 13 C investigations have targeted α‐amino acid and α‐hydroxy acid Strecker products and reactant HCN ; however, δ 13 C values for meteoritic aldehydes and ketones (Strecker precursors) have not yet been reported. As such, the distribution of aldehydes and ketones in the cosmos and their role in prebiotic reactions have not been fully investigated. Here, we have applied an optimized O ‐(2,3,4,5,6‐pentafluorobenzyl)hydroxylamine ( PFBHA ) derivatization procedure to the extraction, identification, and δ 13 C analysis of carbonyl compounds in the Murchison meteorite. A suite of aldehydes and ketones, dominated by acetaldehyde, propionaldehyde, and acetone, were detected in the sample. δ 13 C values, ranging from −10.0‰ to +66.4‰, were more 13 C‐depleted than would be expected for aldehydes and ketones derived from the interstellar medium, based on interstellar 12 C/ 13 C ratios. These relatively 13 C‐depleted values suggest that chemical processes taking place in asteroid parent bodies (e.g., oxidation of the IOM ) may provide a secondary source of aldehydes and ketones in the solar system. Comparisons between δ 13 C compositions of meteoritic aldehydes and ketones and other organic compound classes were used to evaluate potential structural relationships and associated reactions, including Strecker synthesis and alteration‐driven chemical pathways.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.002 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it