Mars Exploration Rovers: chemical composition by the APXS
Bibliographic record
Abstract
The Alpha Particle X-Ray Spectrometers (APXSs) on board the Mars Exploration Rovers (MERs) determine the elemental compositions of Martian samples. Improvements to the version of the instrument flown on the Mars Pathfinder (MPF) mission allow, for the first time, in situ detection and quantification of trace elements such as nickel, zinc, and bromine. The APXS measurements are performed by placing the sensor head against or immediately above the sample surface. A wealth of compositional diversity has been discovered at the two MER landing sites. At Gusev crater, fresh rock surfaces in the plains resemble primitive basalts, while rocks in the Columbia Hills are significantly weathered and enriched in mobile elements such as phosphorus, sulfur, chlorine, and bromine. Sandstones cemented by sulfates as well as evidence for clay formation have also been found in the Columbia Hills. At Meridiani Planum, the layered sedimentary rocks were found to consist primarily of sulfates mixed with siliciclastic debris. Iron-rich spherules and their fragments, confirmed to be hematitic by the Mössbauer spectrometer (MB), are found armoring the soil bedforms as well as embedded in the outcrop rocks. A variety of unusual objects, including an iron-nickel meteorite and a likely ejecta fragment similar to a Martian meteorite, have also been discovered. The elemental compositions of soils analyzed at both sites are remarkably similar, indicative of global-scale homogenization or the similarity of the soil precursors.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.003 | 0.002 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.017 | 0.009 |
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".