Geologic Mapping of Asteroid (52246) Donaldjohanson as observed by NASA’s Lucy mission
Bibliographic record
Abstract
NASA’s Lucy mission will study the Jupiter Trojan asteroids, which are thought to be a physically and compositionally diverse group of primitive planetesimals that originated in the outer Solar System from ~15-30 AU [1]. The Jupiter Trojans are thus early Solar System relics, which are one of the last accessible, stable, small-body groups yet to be explored by a spacecraft. Prior to the first Trojan encounter, (3548) Eurybates in August 2027, Lucy flew by two main-belt asteroids: asteroid (152830) Dinkinesh in November 2023 [2] and asteroid (52246) Donaldjohanson in April 2025 [3], both of which have never before been visited by a spacecraft.Here we present the first geologic map of the entire observed portion of Donaldjohanson. The asteroid is about 8 km long, with a greater than 2 to 1 axis ratio, and appears to be an elongated contact binary composed of two lobes joined by a narrower neck. The primary datasets on which we base the geologic map are images from the L’LORRI camera [4] and the derived shape model [5]. We will present a geologic map that includes both lobes and the neck. We will discuss geologic units, linear features and point features, and an analysis of their distribution across the surface. We will also use geomorphic and structural analyses of these features to make inferences about the present-day subsurface structure and formation mechanism of Donaldjohanson.The Lucy mission is funded through the NASA Discovery program on contract No. NNM16AA08C, and part of this work was funded by ROSES grant 24-LUCYL4PSP-0031.References: [1] Levison, H., et al. (2021) PSJ, 2(5), 171. [2] Levison, H., et al. (2024) Nature, 629, 1015-1020. [3] Levison, H., et al. (2025) This meeting. [4] Weaver, H.A., et al. (2023) SSR, 219, 82. [5] Mottola, S., et al. (2025) This meeting.
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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 | 0.004 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 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".