Cometary evolution and cryovolcanism <sup>1</sup>This article is part of a Special issue that honours the work of Dr. Donald M. Hunten FRSC who passed away in December 2010 after a very illustrious career.
Bibliographic record
Abstract
Recent space observations of cometary nuclei show evidence of internal (cryovolcanic) activity while retaining aspects of their primitive origins. Using discoveries made during the two most recent cometary encounters: EPOXI at 103P/Hartley 2 and Stardust-NExT at 9P/Tempel 1, we test a hypothesis for their physical evolution, which, if true, could provide a unified basis for understanding the relative ages of their surfaces and the causes of a wide range of cometary activity. We show: (i) that the categorization of 103P/Hartley 2 as hyperactive is not a reflection of the extent of activity over the surface of the nucleus for which we find a normal H2O production rate; (ii) that the heterogeneous spatial distribution of CO2 and H2O in the inner comae of 9P/Tempel 1 and 103P/Hartley 2 is best explained by processes associated with cometary activity rather than the presence of primitive compositional heterogeneities in the nucleus; and (iii) that most of the quasi-circular depressions seen on the surface of 9P/Tempel are the result of outburst activity. The apparent absence of circular depressions and large scale layering on 103P/Hartley 2 present a challenge to the evolutionary hypothesis although the small size of its nucleus may ultimately provide an explanation.
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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 | 0.001 | 0.002 |
| 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 | 0.001 |
| Scholarly communication | 0.003 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.022 | 0.003 |
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".