Geologic Context of the OSIRIS-REx Sample Site from High-resolution Topography and Imaging
Bibliographic record
Abstract
Abstract The OSIRIS-REx spacecraft collected a surface sample from Hokioi crater (55.8° N, 42.3° E; diameter ∼20 m) on the asteroid Bennu in 2020 October. We explore the geology of the sample collection site, known as Nightingale, by using digital terrain models, relative albedo maps, and images collected by the OSIRIS-REx spacecraft. Hokioi crater sits at the northwest edge of an older, larger (120 m diameter) crater between two north–south ridges respectively located at roughly 0° and 90° longitude, between which unconsolidated material generally migrates from the geopotential high at the north (+Z) pole to the geopotential low at the equator. The impact that formed Hokioi crater exposed relatively unweathered, fine-grained dark material that we observe within and ejected beyond the crater. The regional slope and steep crater walls to the north of the Nightingale site have enabled a mix of the dark debris and brighter material (which may include carbonates and/or exogenic basalts) surrounding Hokioi crater to migrate onto the crater floor, where the sample was collected; some of this material may be old ejecta excavated from up to 10 m depth when the 120 m diameter crater formed. We therefore expect the OSIRIS-REx sample to include materials of varying brightnesses, compositions, and exposure ages, derived primarily from the 0°–90° longitude quadrant and from as deep as 10 m. The sample may also include material derived from the impactor that formed Hokioi crater. We expect it to have low cohesion (≪0.6 Pa) and a friction angle between 32° and 39°.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".