Characterization and formation of polygonal fractures on Venus
Bibliographic record
Abstract
Fracture theory predicts that polygonal cracks will form in the presence of an isotropic, extensional stress field. On Venus, polygonal fractures are observed on scales several orders of magnitude larger than on Earth, with an average diameter of 1.8 ± 0.9 km. Proposed formation mechanisms include cooling following lava flow emplacement, lithospheric heating, and climate change. Here we examine the characteristics and geologic setting of 204 regions of polygons. Some regions display two spatially overlapping size ranges, with the larger spacing typically 10–25 km. Most polygonal fractures appear to be extensional, but some have the morphology of compressional ridges. Polygons are confined to plains regions and occur in association with shield fields (49%), coronae and coronae‐like features (21.3%), tessera (17.5%), and wrinkle ridges (20%). In locations where polygons occur with shield fields, coronae, or both, they appear to have formed contemporaneously. Formation in conjunction with local heating events is consistent with the lithospheric cooling hypothesis. However, there is almost never the predicted decrease in size away from the center of coronae or shield fields. Only a small percentage of coronae and shield fields contain polygons, indicating that they are not typical of the formation process. The climate change‐induced scenario is consistent with many characteristics of the polygons, including the small and large size ranges, the compressional ridges, and their occurrence with and without evidence of local heating. Although polygons may have diverse origins, including formation by multiple deformation events, overall polygon characteristics support the climate change hypothesis.
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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 | 0.002 | 0.001 |
| 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 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".