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 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 | 0.000 |
| 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".