Engineering topics

Treiman, A. H.

Publications and source records attributed to Treiman, A. H..

At least 37 records · Page 2

NASA NTRS2017

Mineral Trends in Early Hesperian Lacustrine Mudstone at Gale Crater, Mars

The Mars Science Laboratory Curiosity rover landed in Gale crater in August 2012 to study the layered sediments of lower Aeolis Mons (i.e., Mount Sharp), which have signatures of phyllosilicates, hydrated sulfates, and iron oxides in orbital visible/near-infrared observations. The observed mineralogy within the stratigraphy, from phyllosilicates in lower units to sulfates in higher units, suggests an evolution in the environments in which these secondary phases formed. Curiosity is currently investigating the sedimentary structures, geochemistry, and mineralogy of the Murray formation, the lowest exposed unit of Mount Sharp. The Murray formation is dominated by laminated lacustrine mudstone and is approx.200 m thick. Curiosity previously investigated lacustrine mudstone early in the mission at Yellowknife Bay, which represents the lowest studied stratigraphic unit. Here, we present the minerals identified in lacus-trine mudstone from Yellowknife Bay and the Murray formation. We discuss trends in mineralogy within the stratigraphy and the implications for ancient lacustrine environments, diagenesis, and sediment sources.

Rampe, E. B.↗

NASA NTRS2017

A New Type of Foreign Clast in A Polymict Ureilite: A CAI or AL-Rich Chondrule

Introduction: Polymict ureilites are breccias interpreted to represent regolith formed on a ureilitic asteroid [1-3]. They consist of approximately 90-95% clasts of various ureilite types (olivine-pyroxene rocks with Fo 75-95), a few % indigenous feldspathic clasts, and a few % foreign clasts [4-20]. The foreign clasts are diverse, including fragments of H, L, LL and R chondrites, angrites, other achondrites, and dark clasts similar to CC [6,7,9-19]. We report a new type of foreign clast in polymict ureilite DaG 999. Methods: Clast 8 in Dar al Gani (DaG) 999/1 (Museum fur Naturkunde) was discovered during a survey of feldspathic clasts in polymict ureilites [19,20]. It was studied by BEI, EMPA, and X-ray mapping on the JEOL 8530F electron microprobe at ARES, JSC. Petrography and Mineral Compositions: Clast 8 is sub-rounded to irregular in shape, approximately 85 micrometers in diameter, and consists of approximately 68% pyroxene and 32% mesostasis (by area). Part of the pyroxene (top half of clast in Fig. 1a and 2) shows a coarse dendritic morphology; the rest appears massive. Mesostasis may be glassy and contains fine needles/grains of pyroxene. The pyroxene has very high CaO (23.5 wt.%) and Al2O3 (19.7 wt.%), with the formula: (Ca(0.91)Mg(0.63)Fe(0.01)Al(sup VI) (0.38)Cr(0.01)Ti(0.05)1.99 Si2O6. The bulk mesostasis also has very high Al2O3 (approximately 26 wt.%). A bulk composition for the clast was obtained by combining modal abundances with phase compositions (Table 1, Fig. 3). Discussion: The pyroxene in clast 8 has a Ca-Al-(Ti)- rich (fassaitic) composition that is clearly distinct from compositions of pyroxenes in main group ureilites [22] or indigenous feldspathic clasts in polymict ureilites [4-8]. It also has significantly higher Al than fassaite in angrites (up to approximately 12 wt.% [23]), which occur as xenoliths in polymict ureilites. Ca-Al-Ti rich pyroxenes are most commonly found in CAIs, Al-rich chondrules and other types of refractory inclusions in chondrites [21,24-31]. However, the clast 8 pyroxene matches only the most Al-Ca-rich of these, e.g., pyroxenes in type B CAIs in CV3 chondrites [25,30,31], a pyroxene-hibonite spherule and a pyroxene-anorthitespinel fragment from unique CC Acfer 094 [29], and one Al-rich chondrule from Chainpur (LL3.4) [21]. The mineralogy of clast 8 is not consistent with the mineral assemblages of any of these objects (since it lacks hibonite, spinel and/or anorthite), which suggests that it is unrepresentatively sectioned or is a fragment of a more mineralogically diverse object. Its bulk composition (Table 1; Fig. 3) is similar to bulk compositions of some Al-rich chondrules, as well as those of Type C CAIs (which plot in the sp+An+L field in Fig. 3), although it is enriched in silica relative to type C CAIs [e.g., 31]. This suggests a more likely affinity to Al-rich chondrules, although most Al-rich chondrules have less Al-Ca-rich pyroxene [21,26,27]. These bulk compositional comparisons may not be definitive, however, if the clast is unrepresentatively sampled. One of eleven Al-rich chondrules from UOCs described by [21] has textural and compositional characteristics that make it a possible progenitor type for clast 8. This chondrule (Chainpur 1251-14-2) is anorthiteporphyritic, with an interstitial dendritic intergrowth of pyroxene (similar in composition to that in clast 8) and plagioclase [21]. Clast 8 is conceivably a fragment from the interstitial area of such an object. The occurrence of glassy mesostasis (in clast 8) rather than plagioclase may not be a significant difference; it could result from a difference only in cooling rate. Al-rich chondrules with glassy mesostasis are rare, and known occurrences are Ca-poor [26], unlike clast 8. Polymict ureilites are known to contain xenoliths of various chondrites (including OC, R and CC) as well as individual ferromagnesian and silica-pyroxene chondrules probably derived from OC or RC [6,9,15,16,18]. This is the first report of an individual chondritic refractory inclusion as a xenolith in a polymict ureilite. An RC-like sample from anomalous polymict ureilite Almahata Sitta contains CAIs, but they are spinel-rich and not similar to clast 8 [13,14]. Further studies of this clast (which, unfortunately, may not be possible), or the discovery of additional (more representative?) materials of this type would be needed to determine the exact nature of this xenolith and the type of chondrite from which it is derived.

Goodrich, C. A.↗

NASA NTRS2017

Priority Science Targets for Future Sample Return Missions within the Solar System Out to the Year 2050

The Astromaterials Acquisition and Curation Office (henceforth referred to herein as NASA Curation Office) at NASA Johnson Space Center (JSC) is responsible for curating all of NASA's extraterrestrial samples. JSC presently curates 9 different astromaterials collections: (1) Apollo samples, (2) LUNA samples, (3) Antarctic meteorites, (4) Cosmic dust particles, (5) Microparticle Impact Collection [formerly called Space Exposed Hardware], (6) Genesis solar wind, (7) Star-dust comet Wild-2 particles, (8) Stardust interstellar particles, and (9) Hayabusa asteroid Itokawa particles. In addition, the next missions bringing carbonaceous asteroid samples to JSC are Hayabusa 2/ asteroid Ryugu and OSIRIS-Rex/ asteroid Bennu, in 2021 and 2023, respectively. The Hayabusa 2 samples are provided as part of an international agreement with JAXA. The NASA Curation Office plans for the requirements of future collections in an "Advanced Curation" program. Advanced Curation is tasked with developing procedures, technology, and data sets necessary for curating new types of collections as envisioned by NASA exploration goals. Here we review the science value and sample curation needs of some potential targets for sample return missions over the next 35 years.

McCubbin, F. M.↗

NASA NTRS2016

Elemental Gains/Losses Associated with Alteration Fractures in an Eolian Sandstone, Gale Crater, Mars

The Mars Science Laboratory rover Curiosity has traversed up section through approximately 100 m of sedimentary rocks deposited in fluvial, deltaic, lacustrine, and eolian environments (Bradbury group and overlying Mount Sharp group). The Stimson formation unconformably overlies a lacustrine mudstone at the base of the Mount Sharp group and has been interpreted to be a cross-bedded sandstone of lithified eolian dunes. Unaltered Stimson sandstone has a basaltic composition similar to the average Mars crustal composition, but is more variable and ranges to lower K and higher Al. Fluids passing through alteration "halos" adjacent to fractures have altered the chemistry and mineralogy of the sandstone. Elemental mass gains and losses in the alteration halos were quantified using immobile element concentrations, i.e., Ti (taus). Alteration halos have elemental gains in Si, Ca, S, and P and large losses in Al, Fe, Mn, Mg, Na, K, Ni, and Zn. Mineralogy of the altered Stimson is dominated by Ca-sulfates, Si-rich X-ray amorphous materials along with plagioclase feldspar, magnetite, and pyroxenes. The igneous phases were less abundant in the altered sandstone with a lower pyroxene/plagioclase feldspar. Large elemental losses suggest acidic fluids initially removed these elements (Al mobile under acid conditions). Enrichments in Si, Ca, and S suggest secondary fluids (possibly alkaline) passed through these fractures leaving behind X-ray amorphous Si and Ca-sulfates. The mechanism for the large elemental gains in P is unclear. The geochemistry and mineralogy of the altered sandstone suggests a complicated diagenetic history with multiple episodes of aqueous alteration under a variety of environmental conditions (e.g., acidic, alkaline).

Ming, D. W.↗

NASA NTRS2016

Diagenesis Along Fractures in an Eolian Sandstone, Gale Crater, Mars

The Mars Science Laboratory rover Curiosity has been exploring sedimentary deposits in Gale crater since August 2012. The rover has traversed up section through approx.100 m of sedimentary rocks deposited in fluvial, deltaic, lacustrine, and eolian environments (Bradbury group and overlying Mount Sharp group). The Stimson formation lies unconformable over a lacustrine mudstone at the base of the Mount Sharp group and has been interpreted to be a cross-bedded sandstone of lithified eolian dunes. Mineralogy of the unaltered Stimson sandstone consists of plagioclase feldspar, pyroxenes, and magnetite with minor abundances of hematite, and Ca-sulfates (anhydrite, bassanite). Unaltered sandstone has a composition similar to the average Mars crustal composition. Alteration "halos" occur adjacent to fractures in the Stimson. Fluids passing through these fractures have altered the chemistry and mineralogy of the sandstone. Silicon and S enrichments and depletions in Al, Fe, Mg, Na, K, Ni and Mn suggest aqueous alteration in an open hydrologic system. Mineralogy of the altered Stimson is dominated by Ca-sulfates, Si-rich X-ray amorphous materials along with plagioclase feldspar, magnetite, and pyroxenes, but less abundant in the altered compared to the unaltered Stimson sandstone and lower pyroxene/plagioclase feldspar. The mineralogy and geochemistry of the altered sandstone suggest a complicated history with several (many?) episodes of aqueous alteration under a variety of environmental conditions (e.g., acidic, alkaline).

Ming, D. W.↗

NASA NTRS2016

Mineralogy of Mudstone at Gale Crater, Mars: Evidence for Dynamic Lacustrine Environments

The Mars Science Laboratory Curiosity rover landed in Gale crater in August 2012 to assess the habitability of sedimentary deposits that show orbital evidence for diverse ancient aqueous environments. Gale crater contains a 5 km high mound of layered sedimentary rocks in its center, informally named Mount Sharp. The lowermost rocks of Mount Sharp contain minerals that are consistent with a dramatic climate change during Mars' early history. During the rover's traverse across the Gale crater plains to the base of Mount Sharp, Curiosity discovered sedimentary rocks consistent with a fluviolacustrine sequence. Curiosity studied ancient lacustrine deposits at Yellowknife Bay on the plains of Gale crater and continues to study ancient lacustrine deposits in the Murray formation, the lowermost unit of Mount Sharp. These investigations include drilling into the mudstone and delivering the sieved less than 150 micrometers fraction to the CheMin XRD/XRF instrument inside the rover. Rietveld refinement of XRD patterns measured by CheMin generates mineral abundances with a detection limit of 1-2 wt.% and refined unit-cell parameters of minerals present in abundances greater than approximately 5 wt.%. FULLPAT analyses of CheMin XRD patterns provide the abundance of X-ray amorphous materials and constrain the identity of these phases (e.g., opal-A vs. opal-CT). At the time of writing, CheMin has analyzed 14 samples, seven of which were drilled from lacustrine deposits. The mineralogy from CheMin, combined with in-situ geochemical measurements and sedimentological observations, suggest an evolution in the lake waters through time, including changes in pH and salinity and transitions between oxic and anoxic conditions. In addition to a geochemically dynamic lake environment, the igneous minerals discovered in the lake sediments indicate changes in source region through time, with input from mafic and silicic igneous sources. The Murray formation is predominantly comprised of lacustrine mudstone and is 150-200 m thick, suggesting long history of lake environments in Gale crater. Curiosity has traversed through the lowermost approximately 30 m of the Murray formation, and each additional sample provides clues about the climate on early Mars.

Rampe, E. B.↗

NASA NTRS2016

Fluids During Diagenesis and Sulfate Vein Formation in Sediments at Gale Crater, Mars

We model the fluids involved in the alteration processes recorded in the Sheep bed Member mudstones of Yellowknife Bay (YKB), Gale crater, Mars, as revealed by the Mars Science Laboratory Curiosity rover investigations. We compare the Gale crater waters with fluids modeled for shergottites, nakhlites, and the ancient meteorite ALH 84001, as well as rocks analyzed by the Mars Exploration rovers, and with terrestrial ground and surface waters. The aqueous solution present during sediment alteration associated with phyllosilicate formation at Gale was high in Na, K, and Si; had low Mg, Fe, and Al concentrations relative to terrestrial ground waters such as the Deccan Traps and other modeled Mars fluids; and had near neutral to alkaline pH. Ca and S species were present in the 10(exp -3) to 10(exp -2) concentration range. A fluid local to Gale crater strata produced the alteration products observed by Curiosity and subsequent evaporation of this ground water- type fluid formed impure sulfate- and silica-rich deposits veins or horizons. In a second, separate stage of alteration, partial dissolution of this sulfate-rich layer in Yellowknife Bay,or beyond, led to the pure sulfate veins observed in YKB. This scenario is analogous to similar processes identified at a terrestrial site in Triassic sediments with gypsum veins of the Mercia Mudstone Group in Watchet Bay, UK.

Gale Crater↗

NASA NTRS2016

The Foreign Clast Populations of Anomalous Polymict Urelite Almahata Sitta (Asteroid 2008 TC(sub3) and Typical Polymict Ureilites: Implications for Asteroid-Meteorite Connections

Almahata Sitta (AhS) is the first meteorite to originate from an asteroid (2008 TC3) that had been studied in space before it hit Earth [1,2]. It is also unique because the fallen fragments comprise a variety of types: approximately 69% ureilites (achondrites) and 31% chondrites [3]. Two models have been proposed for the origin 2008 TC3: 1) an accretionary model [3,4]; or 2) a regolith model [5,6]. Typical polymict ureilites are interpreted to represent regolith, and contain a few % foreign clasts [7,8]. The most common are dark (CC matrix-like) clasts similar to those in many meteoritic breccias [9]. A variety of other chondrites, as well as achondrites (angrites), have also been reported [7,9,10]. We have been working to determine the full diversity of these clasts [10-13] for comparison with AhS. We discuss implications for mixing of materials in the early solar system and the origin of 2008 TC3.

Goodrich, C. A.↗

NASA NTRS2016

Mineralogy of Eolian Sands at Gale Crater

The Mars Science Laboratory rover Curiosity has been exploring outcrop and regolith in Gale crater since August 6, 2012. During this exploration, the mission has collected 10 samples for mineralogical analysis by X-ray diffraction (XRD), using the CheMin instrument. The CheMin (Chemistry and Mineralogy) instrument on the Mars Science Laboratory rover Curiosity uses a CCD detector and a Co-anode tube source to acquire both mineralogy (from the pat-tern of Co diffraction) and chemical information (from energies of fluoresced X-rays). A detailed description of CheMin is provided in [1]. As part of the rover checkout after landing, the first sample selected for analysis was an eolian sand deposit (the Rocknest "sand shadow"). This sample was selected in part to characterize unconsolidated eolian regolith, but primarily to prove performance of the scoop collection system on the rover. The focus of the mission after Rocknest was on the consolidated sediments of Gale crater, so all of the nine subsequent samples were collected by drilling into bedrock com-posed of lithified sedimentary materials, including mudstone and sandstone. No scoop samples have been collected since Rocknest, but at the time this abstract was written the mission stands poised to use the scoop again, to collect active dune sands from the Bagnold dune field. Several abstracts at this conference outline the Bagnold dune campaign and summarize preliminary results from analyses on approach to the Namib dune sampling site. In this abstract we review the mineralogy of Rocknest, contrast that with the mineralogy of local sediments, and anticipate what will be learned by XRD analysis of Bagnold dune sands.

Achilles, C. N.↗

NASA NTRS2016

High-Temperature, Perhaps Silicic, Volcanism on Mars Evidenced by Tridymite Detection in High-SiO2 Sedimentary Rock at Gale Crater, Mars

The Mars Science Laboratory (MSL) rover, Curiosity, has been exploring sedimentary rocks within Gale crater since landing in August, 2012. On the lower slopes of Aeolis Mons (a.k.a. Mount Sharp), drill powder was collected from a high-silica (74 wt% SiO2) outcrop named Buckskin (BK). It was a surprise to find that the Buckskin sample contained significant amounts of the relatively rare silica polymorph tridymite. We describe the setting of the Buckskin sample, the detection of tridymite by the MSL Chemistry and Mineralogy (CheMin) X-ray diffraction instrument, and detection implications. Geologic setting: The Buckskin outcrop is part of the Murray formation exposed in the Marias Pass area. The formation was previously studied by CheMin in the Pahrump Hills member [1] where three samples of drill fines were analyzed (Confidence Hills (CH), Mojave2 (MJ) and Telegraph Peak (TP) [2]). Assuming approximately horizontal bedding, the Buckskin outcrop is approx.15 m stratigraphically above the bottom of the Pahrump Hills member. Mudstone, generally characterized by fine lamination, is the dominant depositional facies [1]. Buckskin Mineralogical and Chemical Composition: The CheMin instrument and XRD pattern analysis procedures have been previously discussed [3-6]. The diffraction pattern used for quantitative XRD analysis (Fig. 1) is the sum of the first 4 of 45 diffraction images. The remaining images are all characterized by both on-ring and off-ring diffraction spots that we attributed to poor grain motion and particle clumping. Coincident with particle clumping was a significant decrease in the intensity of the tridymite diffraction peaks (Fig. 2a). The derived mineralogical composition of the crystalline component (derived from the first 4 diffraction images) is given in Table 1. The tridymite is well-crystalline and its pattern is refined as monoclinic tridymite (Fig 1). Mineral chemical compositions were derived from XRD unit cell parameters or obtained from stoichiometry. The XRD-calculated amorphous component was 50 +/- 15 wt%. We constrained the value to 60 wt% because it is the minimum value necessary to give a positive Al2O3 concentration for the amorphous component using APXS data for the post-sieve dump pile (Table 2). The amorphous component has high SiO2 (approx.77 wt%) and high anion (SO3+P2O5+Cl ~10 wt%) concentrations. Calculation shows that a cation-anion balance is achieved if the cations in the amorphous component except SiO2 and TiO2, which do not readily form salts, are assumed to be present as amorphous mixed-cation sulfates, phosphates, and chlorides (or perchlorates/ chlorates).

Morris, R. V.↗

NASA NTRS2015

Evidence for Acid-Sulfate Alteration in the Pahrump Hills Region, Gale Crater, Mars

The Pahrump Hills region of Gale crater is a approximately 12 millimeter thick section of sedimentary rock in the Murray formation, interpreted as the basal geological unit of Mount Sharp. The Mars Science Laboratory, Curiosity, arrived at the Pahrump Hills in September 2014 and performed a detailed six-month investigation of the sedimentary structures, geochemistry, and mineralogy of the area. During the campaign, Curiosity drilled and delivered three mudstone samples (targets Confidence Hills, Mojave 2, and Telegraph Peak) to its internal instruments, including the CheMin XRD/XRF.

Rampe, E. B.↗

NASA NTRS2015

Mineralogy of the Pahrump Hills Region, Gale Crater, Mars

The Pahrump Hills region of Gale crater is a approximately 12 millimeter thick section of sedimentary rocks in the Murray formation, interpreted as the basal geological unit of Mount Sharp. The Mars Science Laboratory, Curiosity, arrived at the Pahrump Hills in September, 2014, and performed a detailed six-month investigation of the sedimentary structures, geochemistry, and mineralogy of the area. During the campaign, Curiosity drilled and delivered three rock samples to its internal instruments, including the CheMin XRD/XRF. The three targets, Confidence Hills, Mojave 2, and Telegraph Peak, contain variable amounts of plagioclase, pyroxene, iron oxides, jarosite, phyllosilicates, and X-ray amorphous material. Hematite was predicted at the base of Mount Sharp from orbital visible/near-IR spectroscopy, and CheMin confirmed this detection. The presence of jarosite throughout Pahrump Hills suggests the sediments experienced acid-sulfate alteration, either in-situ or within the source region of the sediments. This acidic leaching environment is in stark contrast to the environment preserved within the Sheepbed mudstone on the plains of Gale crater. The minerals within Sheepbed, including Fe-saponite, indicate these sediments were deposited in a shallow lake with circumneutral pH that may have been habitable.

Rampe, E. B.↗

NASA NTRS2015

Update on the Chemical Composition Of Crystalline, Smectite, and Amorphous Components for Rocknest Soil and John Klein and Cumberland Mudstone Drill Fines at Gale Crater, Mars

We have previously calculated the chemical compositions of the X-ray-diffraction (XRD) amorphous component of three solid samples (Rocknest (RN) soil, John Klein (JK) drill fines, and Cumberland (CB) drill fines) using major-element chemistry (APXS), volatile-element chemistry (SAM), and crystalline- phase mineralogy (CheMin) obtained by the Curiosity rover as a part of the ongoing Mars Science Laboratory mission in Gale Crater. According to CheMin analysis, the RN and the JK and CB samples are mineralogically distinct in that RN has no detectable clay minerals and both JK and CB have significant concentrations of high-Fe saponite. The chemical composition of the XRD amorphous component is the composition remaining after mathematical removal of the compositions of crystalline components, including phyllosilicates if present. Subsequent to, we have improved the unit cell parameters for Fe-forsterite, augite, and pigeonite, resulting in revised chemical compositions for the XRD-derived crystalline component (excluding clay minerals). We update here the calculated compositions of amorphous components using these revised mineral compositions.

Morris, R. V.↗

NASA NTRS2015

Crystal-Chemical Analysis Martian Minerals in Gale Crater

The CheMin instrument on the Mars Science Laboratory rover Curiosity performed X-ray diffraction analyses on scooped soil at Rocknest and on drilled rock fines at Yellowknife Bay (John Klein and Cumberland samples), The Kimberley (Windjana sample), and Pahrump (Confidence Hills sample) in Gale crater, Mars. Samples were analyzed with the Rietveld method to determine the unit-cell parameters and abundance of each observed crystalline phase. Unit-cell parameters were used to estimate compositions of the major crystalline phases using crystal-chemical techniques. These phases include olivine, plagioclase and clinopyroxene minerals. Comparison of the CheMin sample unit-cell parameters with those in the literature provides an estimate of the chemical compositions of the major crystalline phases. Preliminary unit-cell parameters, abundances and compositions of crystalline phases found in Rocknest and Yellowknife Bay samples were reported in. Further instrument calibration, development of 2D-to- 1D pattern conversion corrections, and refinement of corrected data allows presentation of improved compositions for the above samples.

Morrison, S. M.↗

NASA NTRS2015

Mineralogy and Genesis of the Windjana Sandstone, Kimberley Area, Gale Crater, Mars

MSL Curiosity investigated the Windjana sandstone outcrop, in the Kimberley area of Gale Crater, and obtained mineralogical analyses with the CheMin XRD instrument. Windjana is remarkable in containing an abundance of potassium feldspar (and thus K in its bulk chemistry) combined with a low abundance of plagioclase (and low Na/K in its chemistry). The source of this enrichment in K is not clear, but has significant implications for the geology of Gale Crater and of Mars. The high K could be intrinsic to the sediment and imply that the sediment source area (Gale Crater rim) includes K-rich basalts and possibly more evolved rocks derived from alkaline magmas. Alternatively, the high K could be diagenetic and imply that the Gale Crater sediments were altered by K-rich aqueous fluids after deposition.

Treiman, A. H.↗

NASA NTRS2015

Potential Cement Phases in Sedimentary Rocks Drilled by Curiosity at Gale Crater, Mars

The Mars Science Laboratory rover Curiosity has encountered a variety of sedimentary rocks in Gale crater with different grain sizes, diagenetic features, sedimentary structures, and varying degrees of resistance to erosion. Curiosity has drilled three rocks to date and has analyzed the mineralogy, chemical composition, and textures of the samples with the science payload. The drilled rocks are the Sheepbed mudstone at Yellowknife Bay on the plains of Gale crater (John Klein and Cumberland targets), the Dillinger sandstone at the Kimberley on the plains of Gale crater (Windjana target), and a sedimentary unit in the Pahrump Hills in the lowermost rocks at the base of Mt. Sharp (Confidence Hills target). CheMin is the Xray diffractometer on Curiosity, and its data are used to identify and determine the abundance of mineral phases. Secondary phases can tell us about aqueous alteration processes and, thus, can help to elucidate past aqueous environments. Here, we present the secondary mineralogy of the rocks drilled to date as seen by CheMin and discuss past aqueous environments in Gale crater, the potential cementing agents in each rock, and how amorphous materials may play a role in cementing the sediments.

Rampe, E. B.↗

NASA NTRS2015

Confidence Hills Mineralogy and Chemin Results from Base of Mt. Sharp, Pahrump Hills, Gale Crater, Mars

The Mars Science Laboratory (MSL) rover Curiosity recently completed its fourth drill sampling of sediments on Mars. The Confidence Hills (CH) sample was drilled from a rock located in the Pahrump Hills region at the base of Mt. Sharp in Gale Crater. The CheMin X-ray diffractometer completed five nights of analysis on the sample, more than previously executed for a drill sample, and the data have been analyzed using Rietveld refinement and full-pattern fitting to determine quantitative mineralogy. Confidence Hills mineralogy has several important characteristics: 1) abundant hematite and lesser magnetite; 2) a 10 angstrom phyllosilicate; 3) multiple feldspars including plagioclase and alkali feldspar; 4) mafic silicates including forsterite, orthopyroxene, and two types of clinopyroxene (Ca-rich and Ca-poor), consistent with a basaltic source; and 5) minor contributions from sulfur-bearing species including jarosite.

Cavanagh, P. D.↗

NASA NTRS2014

Mineralogy of Fluvio-Lacustrine Sediments Investigated by Curiosity During the Prime Mission: Implications for Diagenesis

The Mars Science Laboratory rover Curiosity investigated sedimentary rocks that were deposited in a diversity of fluvio-lacustrine settings. The entire science payload was employed to characterize the mineralogy and chemistry of the Sheepbed mudstone at Yellowknife Bay and the Windjana sandstone at the Kimberley. Data from the CheMin instrument, a transmission Xray diffractometer, were used to determine the quantitative mineralogy of both samples. The Sheepbed mudstone contains detrital basaltic minerals, calcium sulfates, iron oxides or hydroxides, iron sulfides, trioctahedral smectite, and amorphous material. The mineral assemblage and chemical data from APXS suggest that the trioctahedral smectite and magnetite formed authigenically as a result of alteration of olivine. The apparent lack of higher-grade phyllosilicates (e.g., illite and chlorite) and the presence of anhydrite indicate diagenesis at ~50- 80 ºC. The mineralogy of the Windjana sandstone is different than the Sheepbed mudstone. Windjana contains significant abundances of K-feldspar, low- and high-Ca pyroxenes, magnetite, phyllosilicates, and amorphous material. At least two distinct phyllosilicate phases exist: a 10 Å phase and a component that is expanded with a peak at ~11.8 Å. The identity of the expanded phase is currently unknown, but could be a smectite with interlayer H2O, and the 10 Å phase could be illite or collapsed smectite. Further work is necessary to characterize the phyllosilicates, but the presence of illite could suggest that Windjana experienced burial diagenesis. Candidates for the cementing agents include fine-grained phyllosilicates, Fe-oxides, and/or amorphous material. Interpretations of CheMin data from the Windjana sandstone are ongoing at the time of writing, but we will present an estimate of the composition of the amorphous material from mass balance calculations using the APXS bulk chemistry and quantitative mineralogy from CheMin.

Rampe, Elizabeth B.↗