Nucleation Constraints Lead To Molten Chondrule Precursors in the Early Solar System
Bibliographic record
Abstract
This paper is on an application of nucleation theory and an empirical extension of the quasichemical solution theory of Guggenheim to an ancient bit of nature and to a long standing problem on the origins of meteorites. Chondritic meteorites, which were formed 4.6 billion years ago, contain solid chondrules, which appear to have been liquid silicate droplets formed in a rainlike process in the solar nebula with a gas of solar composition. Such droplets have been experimentally subcooled up to 500 °C below their liquidus temperatures. Just as in terrestrial clouds of subcooled water, silicate droplets should readily form metastably below their liquidus temperatures. Calculations of the condensation of these metastable droplets from a solar gas with an expected nucleation constraint on the formation of metallic iron lead to calculated compositions of chondrules at two different temperatures for each particular pressure that emulate the compositions of two types of porphyritic chondrules in the well-studied meteorite Semarkona, a minimally metamorphosed (or automorphosed), i.e., “most primordial”, chondrite. The two types of chondrules, types IA and II, have very different concentrations of FeO, which are well above the equilibrium concentration because of the nucleation constraint on the formation of metallic iron. The high supersaturation of iron in the gas leads to much higher levels of iron oxide in the chondrules than would be present at equilibrium by driving the reaction H 2 O + Fe ↔ H 2 + FeO to the right. These concepts, if correct, can explain a major part of the chemistries of primordial meteorites and the different relative sizes of the metallic cores of planets. The physics of nucleation of metallic iron and of the crystallization of silicates governs the chemistry of iron compounds such as FeO and leads to metastable liquid chondrule droplets. These significant physicochemical processes explain the origins of two chondrule classes.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 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".