A global Mars dust composition refined by the Alpha‐Particle X‐ray Spectrometer in Gale Crater

Berger, J. A.; Schmidt, M. E.; Gellert, R.; Campbell, John L.; King, P. L.; Flemming, R. L.; Ming, D. W.; Clark, B. C.; Pradler, Irina; VanBommel, S. J.; Minitti, M. E.; Fairén, Alberto González; Boyd, Nicholas; Thompson, L. M.; Perrett, G. M.; Elliott, Beverley; Desouza, E.

doi:10.1002/2015gl066675

Cited by 103 publications

(114 citation statements)

References 44 publications

(103 reference statements)

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“…The P 2 O 5 value from Gale crater agrees with those found by MER. Importantly, our modeled S/Cl ratio agrees with previous S/Cl ratios found for the dust by MER (Gellert et al, ; Morris et al, ) and is within error of the previously published Gale dust composition by Berger et al ().…”

Section: Model Resultssupporting

confidence: 91%

“…Dust has been known to be an important feature of the surface of Mars since the Viking mission (e.g., Pollack et al, ), yet some aspects remain enigmatic, including its origin, which is thought to involve eolian erosion of altered Mars crust (e.g., Bell et al, ; Morris et al, ) or of the Medusa Fossae Formation (Ojha et al, ). The elemental make‐up of Mars dust is generally basaltic but with high concentrations of S and Cl (Berger et al, ). Nanophase ferric oxide (npOx) abundances determined by the Mössbauer spectrometer on board the Mars Exploration Rover Spirit correlate well with SO 3 abundances in soils in Gusev crater (Yen et al, ) and are thought to be an important constituent of the global dust.…”

Section: Introductionmentioning

confidence: 99%

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Dusty Rocks in Gale Crater: Assessing Areal Coverage and Separating Dust and Rock Contributions in APXS Analyses

et al. 2018

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A thin, patchy layer of airfall dust covers rock surfaces examined by the Mars Science Lab rover Curiosity and complicates interpretation of textures in Mars Hand Lens Imager images and compositions determined by Alpha Particle X-ray Spectrometer (APXS). Using three image processing methods, we estimate dust coverages for Mars Hand Lens Imager images of APXS targets to Sol 1512. Dust coverages of as is rock targets range from 6% to 77% (±5% to 10% estimated error). Targets brushed by the Dust Removal Tool range to lower coverages than as is targets, but quality depends on surface type; brushed mudstones have the narrowest range and lowest coverages (11-25%), while sandstones vary, ranging to higher coverages (12-58%). Groups of rocks with similar compositions (APXS classes) can have strong correlations between dust coverage and SO 3 /Cl (up to r = 0.985). Dust can also strongly affect the lightest elements measured (Na to Ca). By comparing paired as is and Dust Removal Tool analyses, using the determined dust coverages, and finding a best fit dust thickness (generally~10 μm), we model relative contributions of the dust and bedrock to extrapolate dust-free compositions for homogeneous APXS classes. The dust is basaltic with high S and Cl. Dust-free rocks have higher SiO 2 and Na 2 O (up to 6.5 wt% and 0.5 wt% higher, respectively) and lower SO 3 and CaO (up to 5.5 wt% and 1.3 wt% lower, respectively) than dusty equivalents. Dust most influences compositions that are very different from average Mars, including the alkali-rich, MgO-poor Jake M class.

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Section: Model Resultssupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Dusty Rocks in Gale Crater: Assessing Areal Coverage and Separating Dust and Rock Contributions in APXS Analyses

et al. 2018

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“…Black line is a 9 point moving average with elevation. Vertical gray band denotes the range in K 2 O/Na 2 O values for average Martian soil [ Taylor and McLennan , ], average Gale crater soil [ O ' Connell‐Cooper et al ., ] and dust [ Berger et al ., ], and the average for shergottites (based on average Na 2 O and K 2 O contents from Treiman and Filiberto [] and the Martian Meteorite Compendium [ Meyer , ]).…”

Section: Resultsmentioning

confidence: 99%

Sorting out compositional trends in sedimentary rocks of the Bradbury group (Aeolis Palus), Gale crater, Mars

et al. 2017

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Sedimentary rocks are composed of detrital grains derived from source rocks, which are altered by chemical weathering, sorted during transport, and cemented during diagenesis. Fluvio‐lacustrine sedimentary rocks of the Bradbury group, observed on the floor of Gale crater by the Curiosity rover during its first 860 Martian solar days, show trends in bulk chemistry that are consistent with sorting of mineral grains during transport. The Bradbury group rocks are uniquely suited for sedimentary provenance analysis because they appear to have experienced negligible cation loss (i.e., open‐system chemical weathering) at the scale of the Alpha Particle X‐ray Spectrometer bulk chemistry analyses based on low Chemical Index of Alteration values and successful modeling of >90% of the (volatile‐free) targets as mixtures of primary igneous minerals. Significant compositional variability between targets is instead correlated to grain‐size and textural characteristics of the rocks; the coarsest‐grained targets are enriched in Al2O3, SiO2, and Na2O, whereas the finer‐grained targets are enriched in mafic components. This is consistent with geochemical and mineralogical modeling of the segregation of coarse‐grained plagioclase from finer‐grained mafic minerals (e.g., olivine and pyroxenes), which would be expected from hydrodynamic sorting of the detritus from mechanical breakdown of subalkaline plagioclase‐phyric basalts. While the presence of a distinctive K2O‐rich stratigraphic interval shows that input from at least one distinctive alkali‐feldspar‐rich protolith contributed to basin fill, the dominant compositional trends in the Bradbury group are consistent with sorting of detrital minerals during transport from relatively homogeneous plagioclase‐phyric basalts.

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“…Molar S/Cl for the MER “bright” dust samples, [ Yen et al ., ] (S/Cl 3.60, 1 σ 0.19), is similar to that identified in the MER basaltic soils (Figure a and Table S3). Molar S/Cl ratios for dust observed on the MSL O‐tray are significantly lower (S/Cl 3.06 ± 0.05) [ Berger et al ., ] (Table S3) but comparable to that identified within soils at Gale (MSL: S/Cl 3.04, 2 σ 0.19). Both the pebbly Gale soils and underlying bedrock are enriched in Cl, relative to the ABS.…”

Section: Discussionmentioning

confidence: 99%

APXS‐derived chemistry of the Bagnold dune sands: Comparisons with Gale Crater soils and the global Martian average

et al. 2017

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We present Alpha‐Particle X‐ray Spectrometer (APXS) data for the active Bagnold dune field within the Gale impact crater (Mars Science Laboratory (MSL) mission). We derive an APXS‐based average basaltic soil (ABS) composition for Mars based on past and recent data from the MSL and Mars Exploration Rover (MER) missions. This represents an update to the Taylor and McLennan (2009) average Martian soil and facilitates comparison across Martian data sets. The active Bagnold dune field is compositionally distinct from the ABS, with elevated Mg, Ni, and Fe, suggesting mafic mineral enrichment and uniformly low levels of S, Cl, and Zn, indicating only a minimal dust component. A relationship between decreasing grain size and increasing felsic content is revealed. The Bagnold sands possess the lowest S/Cl of all Martian unconsolidated materials. Gale soils exhibit relatively uniform major element compositions, similar to Meridiani Planum and Gusev Crater basaltic soils (MER missions). However, they show minor enrichments in K, Cr, Mn, and Fe, which may signify a local contribution. The lithified eolian Stimson Formation within the Gale impact crater is compositionally similar to the ABS and Bagnold sands, which provide a modern analogue for these ancient eolian deposits. Compilation of APXS‐derived soil data reveals a generally homogenous global composition for Martian soils but one that can be locally modified due to past or extant geologic processes that are limited in both space and time.

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A global Mars dust composition refined by the Alpha‐Particle X‐ray Spectrometer in Gale Crater

Cited by 103 publications

References 44 publications

Dusty Rocks in Gale Crater: Assessing Areal Coverage and Separating Dust and Rock Contributions in APXS Analyses

Dusty Rocks in Gale Crater: Assessing Areal Coverage and Separating Dust and Rock Contributions in APXS Analyses

Sorting out compositional trends in sedimentary rocks of the Bradbury group (Aeolis Palus), Gale crater, Mars

APXS‐derived chemistry of the Bagnold dune sands: Comparisons with Gale Crater soils and the global Martian average

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