In and Out – Venusian atmospheric chlorine abundance provides evidence of extensive in-gassing.
Bibliographic record
Abstract
Venus is now inhospitable, and its geological history remains shrouded by its hot, dense atmosphere. However, this may not have always been the case and Venus may have once been more Earth-like and perhaps even habitable 1 . Although there is little data on the planet's surface and atmospheric compositions, what is available from the pioneering landers of the Venera (1970-81) and Vega (1985-85) missions and subsequent observations of the atmosphere pose many questions. One long-standing enigma is the fate of Venusian chlorine. On Earth, chlorine is concentrated in the Earth's oceans, which contain around 1.9% chlorine by weight. The concentration of terrestrial chlorine in seawater is a consequence of efficient planetary outgassing, a mechanism supported by our atmosphere's nitrogen and noble gas composition. This planetary scale outgassing of the mantle resulted in >90% of Earth's entire chlorine budget being present on the terrestrial surface. The nitrogen composition of the Venusian atmosphere supports the hypothesis that Venus has also witnessed a similar degree of mantle outgassing to the Earth. However, unlike Earth, chlorine now appears to be almost entirely absent from the Venusian atmosphere. If, as the composition of the Venusian atmosphere suggests, chlorine did out-gas from the Venusian mantle, why is it absent from the present-day surface? Recent work has shown that, contrary to long-held beliefs, chlorine is highly soluble in silicate melts, which suggests its loss from the Venusian surface may be a consequence of the extensive volcanism seen on Venus and the production of low-degree, alkali-rich melts. Given the physical conditions of the Venusian atmosphere/surface interface, we show that the sequestration of chlorine into erupted silicate melts would be efficient. On cooling, such melts will crystalise halidebearing minerals (e.g. sodalite, apatite) with melt compositions consistent with in-situ Venera measurements, and suggestions of active rifting and a putative Venusian geotherm.
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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 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 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".