Cosmic Ray Irradiation of Interstellar Ices on Sulfur-Rich Grains: A Possible Source of Sulfur-Bearing Molecules
Bibliographic record
Abstract
High Resolution Image Download MS PowerPoint Slide The major reservoir of sulfur in dense interstellar clouds is still largely unknown, although a growing body of evidence suggests that it may exist in a refractory form (i.e., as minerals or allotropes of the element). Therefore, it is possible that the irradiation of sulfur-free interstellar ices on top of sulfur-rich refractory grain components by cosmic rays or stellar winds may result in the formation of simple inorganic sulfur molecules that could be readily detected by ground- or space-borne telescopes. In this study, we have irradiated neat ices of O 2, CO, CO 2, and H 2 O on top of layers of allotropic sulfur at 20 K using 1 MeV He + ions as a mimic of space radiation. Experiments with CO 2 and H 2 O ices were also repeated at 70 K to provide data obtained under conditions more relevant to icy bodies in the outer solar system for comparative purposes. We have found qualitative mid-infrared spectroscopic evidence for the synthesis of SO 2, CS 2, OCS, and H 2 SO 4 hydrates, but not H 2 S, in our experiments and have quantified the efficiency of their formation by calculating the G -value (i.e., the number of molecules formed per 100 eV of energy deposited) for each ice-refractory system. Overall, SO 2 and CS 2 are the most commonly observed products in our experiments, although the highest G -value was that for H 2 SO 4 hydrates formed as a result of the irradiation of H 2 O ice on top of sulfur at 70 K. An important outcome of our study is that our experimental results are consistent with recent observational surveys that suggest SO 2 formation in interstellar ices proceeds primarily via an “energetic” route involving radiolytic processes, while OCS forms as a result of “nonenergetic” processes such as atom or radical addition reactions.
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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 | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".