Effects of extreme cold and aridity on soils and habitability: McMurdo Dry Valleys as an analogue for the Mars Phoenix landing site
Bibliographic record
Abstract
Abstract The McMurdo Dry Valleys are among the driest, coldest environments on Earth and are excellent analogues for the Martian northern plains. In preparation for the 2008 Phoenix Mars mission, we conducted an interdisciplinary investigation comparing the biological, mineralogical, chemical, and physical properties of wetter lower Taylor Valley (TV) soils to colder, drier University Valley (UV) soils. Our analyses were performed for each horizon from the surface to the ice table. In TV, clay-sized particle distribution and less abundant soluble salts both suggested vertical and possible horizontal transport by water, and microbial biomass was higher. Alteration of mica to short-order phyllosilicates suggested aqueous weathering. In UV, salts, clay-sized materials, and biomass were more abundant near the surface, suggesting minimal downward translocation by water. The presence of microorganisms in each horizon was established for the first time in an ultraxerous zone. Higher biomass numbers were seen near the surface and ice table, perhaps representing locally more clement environments. Currently, water activity is too low to support metabolism at the Phoenix site, but obliquity changes may produce higher temperatures and sufficient water activity to permit microbial growth, if the populations could survive long dormancy periods (∼10 6 years).
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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 | 0.001 |
| 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 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".