Basement controls on the scale of giant polygons in Utopia Planitia, Mars
Bibliographic record
Abstract
We investigate the role of buried basement topography in controlling the scale of the giant polygons of Utopia Planitia (49°N, 233°W), Mars. Thermal Emission Imaging System (THEMIS) Infrared Daytime image mosaics reveal ∼6 km average spacing of polygon troughs along selected basin‐radial transects. If graben spacing correlates to thickness of the Utopia basin sediments, this measured trough spacing suggests ∼3 km of sediment, in contrast to inferences of 1–2 km thick sediments within this portion of the basin. Irregular basement topography can influence trough development within the contracting sediments by localizing stresses at the top of basement slopes so that the trough spacing correlates to topographic variations rather than layer thickness. Along the slopes, locally large strains responsible for graben development may develop with only modest levels of sediment contraction. Mars Orbiter Laser Altimeter (MOLA) data from the highlands region, which may represent the buried topography in Utopia basin, are used to create a stochastic suite of numerical simulations of the Utopia basin, where fracture seeds along the base of the model represent potential basement topography beneath the basin. At low strain, our models that simulate wet, fine sediment produce surface fractures with ∼4–7 km spacing, which matches the spacing of troughs in the polygonal terrain of the Utopia basin. This match supports the idea that buried topography below contracting wet sediments may exert primary control on the scale of polygonal troughs. Furthermore, volumetric contraction can produce locally high extensional strains with or without a contribution from tectonic uplift.
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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 | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".