The Adiabatic Heat Flux through the Top of the Core of Ancient Vesta from High-P,T Resistivity Experiments
Bibliographic record
Abstract
Heat flow mechanisms in terrestrial planetary cores contribute to geophysical processes with broader significance such as the generation of a magnetic field. Thermal convective flow in a planetary core may be found with the combination of adiabatic heat flow estimates—which this study seeks to estimate—and thermal evolution models of total heat flow across the core-mantle boundary. Experimental data constraining the effects of light elements on these processes is still needed. In the case of asteroid Vesta, the core is expected to be composed of Fe alloyed with 13-16wt% S (Steenstra et al., 2019) and 1-2wt% Si (Pringle et al., 2013).To simulate the conditions of the early Vestan core, the resistivity of Fe alloyed with 16wt% S and 2wt% Si (Fe-16S-2Si) was measured at high pressures and into the liquid state. A 1000-ton cubic anvil press applied a static pressure of 2, 3, 4, or 5 GPa on the sample. The resistivity of Fe-16S-2Si was then calculated from the voltage drop and constant current across the sample at 300-2000 K along with post-experimental geometry measurements.With the electrical resistivity data, the thermal conductivity of Fe-16S-2Si is estimated using the Wiedemann-Franz Law. For 2-4 GPa, a thermal conductivity of 11+1.5 W/m/K is found. For the top of the core of ancient Vesta, an adiabatic heat flux of 0.3-0.4 mW/m2 is derived. These results indicate that the light elements expected in the Vestan core have a large effect on the thermodynamic properties, including more than halving the expected adiabatic heat flow. Since the total heat flux across the early Vestan core-mantle boundary has been previously estimated as >10 mW/m2 (Weiss et al., 2010), thermal convection alone may account for the magnetic dynamo in early Vesta with the presence of light alloying elements.References:Pringle, E.A., Savage, P.S., Badro, J., Barrat, J.-A., Moynier, F., 2013. Redox state during core formation on asteroid 4-Vesta, Earth and Planetary Science Letters, v. 373, p. 75-82.Steenstra, E.S., Dankers, D., Berndt, J., Klemme, S., Matveev, S., van Westrenen, W., 2019. Significant depletion of volatile elements in the mantle of asteroid Vesta due to core formation, Icarus, v. 317, p. 669-681.Weiss, B.P., Gattacceca, J., Stanley, S., Rochette, P., Christensen, U.R., 2010. Paleomagnetic Records of Meteorites and Early Planetesimal Differentiation, Space Science Reviews, v. 152, p. 341-390.
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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 | 0.000 | 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) | 0.002 | 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".