Terrestrial constraints on H2 generation during Martian serpentinization
Notice bibliographique
Résumé
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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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,001 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,001 |
| Études des sciences et des technologies | 0,001 | 0,001 |
| Communication savante | 0,001 | 0,001 |
| Science ouverte | 0,000 | 0,001 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,003 | 0,001 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».