Convection in a catastrophic flood deposit as the mechanism for the giant polygons on Mars
Bibliographic record
Abstract
A formational mechanism for the large‐scale polygons that are defined by intersecting fractures in the northern plains of Mars is proposed in this work. The presented model is based on Rayleigh convection of interstitial water driven by an unstable density/temperature gradient within a saturated, porous medium. Catastrophic emplacement of water‐rich sediments into the Martian northern plain basins could have provided a thick sedimentary layer in which Rayleigh convection could have occurred. Convection within this active layer is proposed to have differentially thawed an underlying ice‐rich permafrost layer that had been at the planet's surface before being rapidly buried. The resulting morphology of the permafrost subsurface is thought to have resembled the scalloped solid‐liquid interface morphology produced in terrestrial convective flow visualization studies. The exact size and shape of the scallops on the frozen subsurface would have been controlled by the dimensions of the convection cells, which are estimated to have had width‐to‐depth ratios of between 3.4 and 4.5. Subsequent stresses (e.g., gravity and bending stresses) would have produced maximum tensile stresses in the overlying sediments preferentially above the subsurface topographic highs as described previously by McGill and Hills [1992]. Additional desiccation of the sediments would have required contraction of the sediment cover and would have produced large‐scale polygonal fractures along the preexisting weaknesses located above the raised subsurface topography. Thus the underlying subsurface geometric morphology would have been translated to the surface and would be represented by the large‐scale polygonal fractures visible in the Viking Orbiter and Mars Global Surveyor images of the Martian northern plains.
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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 | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".