Evidence for the Disproportionation of Iron in a Eucrite Meteorite: Implications for Impact Processes on Vesta
Bibliographic record
Abstract
Abstract Pure metallic iron is a common component in extraterrestrial samples (e.g., ordinary chondrite, returned lunar samples), and is thought to be an indicator of extremely reducing conditions. However, tiny pure metallic iron (<1 mm) particles are rarely found in Howardite–Eucrite–Diogenite meteorites, and their formation mechanism on Vesta is poorly understood. Sub‐micron sized pure metallic iron particles were identified by transmission electron microscope studies of a melt pocket in the basaltic eucrite meteorite Northwest Africa 11592. Our results demonstrate that the pure metallic iron likely formed through a dissociation reaction of ferrous iron (i.e., 3Fe 2+ = Fe 0 + 2Fe 3+ ) in pyroxene. Another disproportionation reaction product, ferric iron, was confirmed to be incorporated into Al‐rich clinopyroxene in the melt pocket by electron energy loss spectra analyses. The temperature conditions required for the formation of the melt pocket are estimated to be above 1,310°C, as indicated by the crystallization of nano‐sized hercynite within acicular plagioclase. Such high temperatures on Vesta could only have been reached if an impact occurred during peak thermal metamorphism, early in the asteroid's evolution. This formation mechanism of these pure metallic iron particles could play a role in redox environment of the Vesta.
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How this classification was reachedexpand
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 | 0.001 |
| 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 | 0.000 |
| 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, 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".