Terrestrial constraints on H2 generation during Martian serpentinization
Bibliographic record
Abstract
Serpentinization, the water-driven alteration of olivine-rich rocks, plays an integral role in solar system evolution. While much attention has been directed towards the role of serpentinization in the evolution of our own planet, it has also been proposed as a mechanism for warming and stabilizing liquid water on early Mars, controlling the fate of the Martian hydrosphere, and originating life early in the planet’s history. Because olivine is widespread on the Martian surface and highly reactive in the presence of water, many researchers have hypothesized that serpentinization would have been common during periods of Martian history when liquid water was present. Observations of serpentine, the most abundant by-product of serpentinization, in intimate association with olivine on the Martian surface lends fundamental support to this hypothesis. H2 and organic carbon production during typical serpentinization on Earth is fundamentally limited by the modest quantities of Fe in terrestrial mantle olivine, which is typically composed of just 10% of the Fe-endmember, fayalite. To explore how this limitation would differ during Martian serpentinization, we compiled analyses of olivines in Martian meteorites and those analyzed by Curiosity in Gale Crater, Mars. The results show that even the most magnesian Martian olivines contain around twice the Fe content of terrestrial mantle olivine, and most contain much more. Thus, to gain a better understanding of H2 and organic carbon production during Martian serpentinization, we must study serpentinization of atypical, Fe-rich olivines on Earth. To this end, we have performed and compiled analyses of serpentinites of the Duluth Complex (USA), which solidified from tholeiitic magmas broadly similar to those that produced the Martian crust and contains ferroan olivines representative of those on Mars. The data show increases in Fe(III)/Fe(tot) with increasing extents of serpentinization (as measured by H2O content) that mimic the trends observed during serpentinization of terrestrial mantle rocks. However, because of the much higher primary fayalite content, the Duluth Complex serpentinites produced around 5 times the H2 at any given extent of serpentinization than those in an equivalent compilation of terrestrial serpentinites. This observation implies that even weakly serpentinized (20%) rocks on Mars would have produced as much H2 as fully serpentinized terrestrial mantle peridotite, and a formation as large and stratigraphically continuous as the Olivine Bearing Unit in Jezero Crater could have produced a very substantial amount of H2, even if it were only partially serpentinized. Thus, although orbiter observations suggest serpentine may be uncommon on the Martian surface, this does not necessarily indicate that serpentinization, and the reduced gases that it produced, did not play a significant role in the planet’s biogeochemical evolution.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
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".