Venus surface compositions suggest upper mantle temperatures like Earth, so why is there no magnetic field?
Bibliographic record
Abstract
The interior of Venus remains a mystery and, it is challenging to reconcile the available meager observations. The leading theory for the absence of a Venusian magnetic field is that heat within Venus remains trapped beneath the stagnant lid, raising the mantle temperature and limiting flow through the core-mantle boundary. While there are only three surface compositions from the Venera and Vega landers, they are consistent with Mid-Ocean Ridge Basalts (MORB) or Ocean Island Basalts (OIB) implying that in the melting region the mantle of Venus is nothotter than the mantle of Earth. This is a surprising result because stagnant (or squishy) lid planets have hotter interiors than mobile lid planets implying that Venus has not been in the stagnant (or squishy) lid mode of convection for much of its evolution or, another heat transport mechanism—such as heat piping—has played a critical role in the flux of heat through the lithosphere of Venus. We see little change in the geoid or topography power spectra between the calculations suggesting that the presence or absence of lithospheric mobility has only a modest impact on the large-scale geoid or topography. While the patterns of the geoid or topography are not likely to be matched by any convection calculation, the power spectrum is independent of coordinate system and thus, a more robust comparison between calculation and planet. The cases we have found predict a significant heat flux from the core to the mantle—as long as 1000 Myr after an overturn event—inconsistent with the absence of a present-day magnetic field and the estimated age of the surface from cratering, the next step will be to consider a Basal Magma Ocean (BMO) to sequester heat within the core.
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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 | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.005 | 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".