Molecular biosignatures in planetary analogue salts: implications for transport of organics in sulfate-rich brines beyond Earth
Bibliographic record
Abstract
Salt minerals precipitated during evaporation or freezing of brines can capture organic and geochemical biosignatures, preserving crucial information about the aqueous environment at the time of their formation [1]. Such salts are prevalent throughout the Solar System, including Mars, icy moons, and asteroids. Their association with liquid water environments make salts high priority astrobiology targets [2].We analysed the lipid fraction preserved within the contemporary Lost Hammer salt deposit (Canadian High Arctic) - an analogue to extraterrestrial salt systems - and paired this with space mission-relevant evolved gas analysis. Our findings show microbial organic matter (fatty acids and n-alkanes) is incorporated into Lost Hammer salts, which comprise polyhydrated sulfates and chlorides. We find a difference in the relative abundance of fatty acids vs. n-alkanes indicating how these biosignatures evolve across active and non-active parts of the spring. We also find differences between pristine salt-organic mixtures and deposits that may have been remobilised by subsequent dissolution and recrystallisation. In this system, n-alkanes have the highest preservation potential, surviving the likely dissolution and recrystallisation of hydrated salt phases. This is important for considering the fate of organic matter on icy moons such as Europa, where salts emplaced on the surface by briny extrusions may have undergone fractional crystallisation, or where subsurface salts are remobilised by localised melting. It is also relevant for once active brine systems on Mars, where cycles of groundwater recharge and/or deliquescence led to dissolution and re-precipitation of evaporitic salts. Schopf, J. W., Farmer, J. D., Foster, I. S., Kudryavtsev, A. B., Gallardo, V. A., & Espinoza, C. (2012). Gypsum-permineralized microfossils and their relevance to the search for life on Mars. Astrobiology, 12(7), 619-633. Phillips, M. S., McInenly, M., Hofmann, M. H., Hinman, N. W., Warren-Rhodes, K., Rivera-Valentín, E. G., & Cabrol, N. A. (2023). Salt constructs in paleo-lake basins as high-priority astrobiology targets. Remote Sensing, 15(2), 314.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".