Dependence of secondary crater characteristics on downrange distance: High‐resolution morphometry and simulations
Bibliographic record
Abstract
Abstract On average, secondary impact craters are expected to deepen and become more symmetric as impact velocity ( v i ) increases with downrange distance ( L ). We have used high‐resolution topography (1–2 m/pixel) to characterize the morphometry of secondary craters as a function of L for several well‐preserved primary craters on Mars. The secondaries in this study ( N = 2644) span a range of diameters (25 m ≤ D ≤400 m) and estimated impact velocities (0.4 km/s ≤ v i ≤2 km/s). The range of diameter‐normalized rim‐to‐floor depth ( d / D ) broadens and reaches a ceiling of d / D ≈0.22 at L ≈280 km ( v i = 1–1.2 km/s), whereas average rim height shows little dependence on v i for the largest craters ( h / D ≈0.02, D > 60 m). Populations of secondaries that express the following morphometric asymmetries are confined to regions of differing radial extent: planform elongations ( L < 110–160 km), taller downrange rims ( L < 280 km), and cavities that are deeper uprange ( L < 450–500 km). Populations of secondaries with lopsided ejecta were found to extend to at least L ∼ 700 km. Impact hydrocode simulations with iSALE‐2D for strong, intact projectile and target materials predict a ceiling for d / D versus L whose trend is consistent with our measurements. This study illuminates the morphometric transition from subsonic to hypervelocity cratering and describes the initial state of secondary crater populations. This has applications to understanding the chronology of planetary surfaces and the long‐term evolution of small crater populations.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 | 0.001 |
| 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 teacher head, 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".