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79 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Mineralogy, Provenance, and Diagenesis of a Potassic Basaltic Sandstone on Mars: CheMin X-Ray Diffraction of the Windjana Sample (Kimberley Area, Gale Crater)

The Windjana drill sample, a sandstone of the Dillinger member (Kimberley formation, Gale Crater, Mars), was analyzed by CheMin X-ray diffraction (XRD) in the MSL Curiosity rover. From Rietveld refinements of its XRD pattern, Windjana contains the following: sanidine (21% weight, approximately Or(sub 95)); augite (20%); magnetite (12%); pigeonite; olivine; plagioclase; amorphous and smectitic material (approximately 25%); and percent levels of others including ilmenite, fluorapatite, and bassanite. From mass balance on the Alpha Proton X-ray Spectrometer (APXS) chemical analysis, the amorphous material is Fe rich with nearly no other cations-like ferrihydrite. The Windjana sample shows little alteration and was likely cemented by its magnetite and ferrihydrite. From ChemCam Laser-Induced Breakdown Spectrometer (LIBS) chemical analyses, Windjana is representative of the Dillinger and Mount Remarkable members of the Kimberley formation. LIBS data suggest that the Kimberley sediments include at least three chemical components. The most K-rich targets have 5.6% K2O, approximately 1.8 times that of Windjana, implying a sediment component with greater than 40% sanidine, e.g., a trachyte. A second component is rich in mafic minerals, with little feldspar (like a shergottite). A third component is richer in plagioclase and in Na2O, and is likely to be basaltic. The K-rich sediment component is consistent with APXS and ChemCam observations of K-rich rocks elsewhere in Gale Crater. The source of this sediment component was likely volcanic. The presence of sediment from many igneous sources, in concert with Curiosity's identifications of other igneous materials (e.g.,mugearite), implies that the northern rim of Gale Crater exposes a diverse igneous complex, at least as diverse as that found in similar-age terranes on Earth.

Treiman, Allan H.↗
NASA NTRS2018

Design and Characteristics of Hydroxyapatites: Effect of Radiation

Hydroxyapatites single crystals have been investigated their applications as the laser host material. Czochralksi and flux growth methods have been utilized to achieve single crystals. Because of their bioactivities with tissues these have attracted interest for bone applications. For low temperature processing we have used several techniques. We utilized some organic melt and oriented the grains by the directional solidification method. This organic treated material has different characteristics than coarsened oxide materials. Our approach involved low temperature processing using nano-engineered powders of the material system MgO-Na2O-K2O-CaO-SrO-SiO2 and also borates were processed by sintering and grain growth. Our results indicate that substitution of calcium and strontium with some other elements such as gallium and magnesium have great potential to improve the mechanical properties of bones.

Bhavsar, Jayati↗
NASA NTRS2018

Design and Characteristics of Hydroxyapatites: Effect of Radiation

We have prepared silicate based hard materials and have processed it with organic flux. Because of the bioactivities of hydroxyapatites with tissues, this class of materials have attracted interest for bone applications. We have utilized low temperature processing techniques. Organic melt was used and the directional solidification method to cast the shaped sample. This organic treated material has different characteristics than coarsened oxide materials. Our approach involved low temperature processing using nano and micron sized powders of the material system Na2O-K2O-CaO- MgO-Ga2O3-SiO2, and titanates were processed by sintering and grain growth. Our results indicate that substitution of gallium and magnesium or titanium with some variation in processing methods have great potential to improve the glassy characteristics without decreasing the mechanical properties of bones. Effect of radiation on bone was studied by exposing with commercially available Cs137 gamma ray source. It was observed that electrical resistivity increased due to radiation exposure for this system.

Bhavsar, Jayati↗
NASA NTRS2018

Effect of Radiation on Biologically Active Glasses

Multifunctional hydroxyapatites single crystals have been studied for their applications as the laser host material since past several decades. It is only recently their potential has been evaluated for bioactive materials. In the past researches, Czochralski and flux growth methods have been utilized to achieve single crystals. We have used low temperature processing techniques for synthesis. Organic melt was used to achieve oriented fibers by the directional solidification method. This organic treated material has different characteristics than coarsened oxide materials. Our approach involved low temperature processing using nano engineered powders of the material system Na2O-K2O-CaO- MgO-SrO-SiO2. Also, borates were processed by sintering and grain growth. Effect of -ray was studied by measuring the electrical characteristics of radiated samples. Our experiments to further improve mechanical characteristics indicate that substitution of calcium with some other elements such as gallium have great potential to improve the radiation hardening and mechanical properties of bones.

Tufail, Areeba↗
NASA NTRS2018

Reworking and Diagenesis of Martian Soil: Pathway to Murray Formation Sediments?

In Gale crater, the Curiosity Mars rover has climbed over 300 meters of the Murray formation from the base of the Pahrump Hills to the crest of Vera Rubin Ridge. We discuss the possibility that fine-grained mudstone of the Murray formation is a diagenetic product of sediments with a chemical and mineralogical composition similar to present-day martian soil. Typical (low Ca-sulfate) Murray samples have Na2O, Al2O3, SiO2, SO3, TiO2 and FeOT concentrations within 10% (relative) of average martian soil. These oxides constitute ~85% of each sample. The Al/Si and Ti/Si ratios of Murray samples are comparable to average martian soil but distinct from other martian geologic units. Percentage difference in P2O5, Cl, K2O, Cr2O3, MnO, Ni, Zn, Br, and Ge between soil and Murray samples generally exceed 10%, but these elements and oxides amount to less than 4% of the samples. These constituents are highly variable in Murray mudstone and may reflect mobility in fluid interactions. Large discrepancies in MgO and CaO with ~50% lower concentrations in the Murray samples (~2% absolute differences) are indicative of open-system alteration if the Murray mudstone originated from soil-like material. Mineralogically, martian soil is dominated by plagioclase feldspar, pyroxenes, and olivine with minor hematite, magnetite, and Ca-sulfate. In comparison, Murray samples generally have less feldspar and pyroxene, little to no olivine, more iron oxides and Ca-sulfates, and Fe-containing phyllosilicates. If Murray mudstone originated from a Mars soil composition, aqueous alteration could have converted olivine and pyroxenes to iron oxides and phyllosilicates. Intermixed or zoned plagioclase feldspars could have lost a larger portion of calcic constituents, consistent with susceptibility to weathering, resulting in a change from ~An55 (soil) to ~An40 (Murray). This alteration could be consistent with the major element chemistry, including the small decrease in MgO and CaO. A subsequent influx of minor/trace elements and Ca-sulfate, e.g. from groundwater, would be required. In this diagenetic scenario, the bulk of the alteration would have been nearly isochemical, suggesting limited mineral segregation and aqueous alteration during transport from the drainage basin or a significant direct aeolian contribution to the Murray sediments.

Yen, Albert S.↗
NASA NTRS2021

Post-Landing Major Element Quantification Using SuperCam Laser Induced Breakdown Spectroscopy

The SuperCam instrument on the PerseveranceMars 2020 rover uses a pulsed 1064 nm laser to ablate targets at a distance and conduct laser induced breakdown spectroscopy (LIBS) by analyzing the light from the resulting plasma. SuperCam LIBS spectra are preprocessed to remove ambient light, noise, and the continuum signal present in LIBS observations. Prior to quantification, spectra are masked to remove noisier spectrometer regions andspectra are normalized to minimize signal fluctuations and effectsof target distance.In some cases, the spectra are also standardized or binned prior to quantification. To determine quantitative elemental compositionsof diverse geologic materials at Jezero crater, Mars, we use a suite of 1198 laboratory spectra of 334 well-characterized reference samples. The samples were selected to span a wide range of compositions and include typical silicate rocks, pure minerals (e.g.,silicates, sulfates, carbonates, oxides),more unusual compositions (e.g.,Mn oreand sodalite), andreplicates of the sintered SuperCam calibration targets (SCCTs) onboardthe rover. For each major element (SiO2, TiO2, Al2O3, FeOT, MgO, CaO, Na2O, K2O), the database was subdivided into five“folds” with similar distributions of the element of interest. One fold was held out as an independent test set, and the remaining fourfolds were used to optimize multivariate regression models relating the spectrum to the composition. We considered a variety of models, and selected several for further investigation for each element, based primarily on the root mean squared error of prediction (RMSEP) on the test set, when analyzed at 3m. In cases with several models of comparable performance at 3 m, we incorporated the SCCT performance at different distances to choose the preferred model. Shortly after landing on Mars and collecting initial spectra of geologic targets, we selected one model per element. Subsequently, with additional data from geologic targets, some models were revised to ensure results that are more consistent with geochemical constraints. The calibration discussed here is a snapshot of an ongoing effort to deliver the most accurate chemical compositions with SuperCam LIBS.

Mars 2020↗
NASA NTRSDate not supplied

Tin-Essako 001: A Metal-Rich Ureilite?

Introduction: Metal-rich achondrites include a variety of types, and likely have a variety of origins. Models range from gravitational mixing at the core-mantle boundaries of differentatiated asteroids, to complex impact mixing scenarios. We describe a new type of metal-rich achondrite that might be the first metal-rich ureilite. Sample: Tin-Essako (TE) 001 (~4.3 g) was found in Mali in 2020 and purchased by Jay Piatek in 2021. It was classified as a metal-rich ungrouped achondrite, with olivine and oxygen isotope (d18O=8.2810‰, d17O=3.718‰, avg. 3) compositions suggesting affinity to ureilites [1]. We studied one polished section (~187.7 mm2) of TE 001. Petrography: TE 001 consists of ~60% metal and 40% silicates, heterogeneously distributed. The metal is largely fresh, but iron oxides (presumably terrestrial) occur along one edge and in some patches and veins in the interior. The silicates are dominantly olivine (≥90%), with melt-textured areas of plagioclase + Si-rich glass. Minor phases include chromite and carbon. Olivine occurs as rounded grains (up to ~2.5 mm) in metal, commonly with rims of melt-textured plagioclase + glass. Olivine also occurs in more massive areas having a “honeycomb” texture, with rounded olivine “cells” surrounded by an interstitial network of reduced olivine riddled with tiny metal grains, plus melt-textured plagioclase + Si-rich glass. Chromite occurs as subhedral to rounded grains; smaller grains (30-250 mm) are included in olivine and a few larger grains (400-500 mm) are isolated within metal. A carbon phase occurs as lacy-textured rims around olivine grains in metal, or small patches within metal. Mineral Compositions: The olivine (excluding interstitial areas) is Fo 73.9±0.5, with 0.25±0.02 wt.% CaO, 0.31±0.01 wt% Cr2O3, 0.01 wt.% NiO, and molar Fe/Mn=49.8±2.2 (53 analyses). Olivine in interstitial areas has Fo up to at least 91. Smaller chromite grains have Fe# (molar Fe/[Fe+Mg]) = 0.54±0.01, Cr# (molar Cr/[Cr+Al]) = 0.52±0.01, 0.52±0.02 wt.% V2O3 and 0.21±0.04 wt% ZnO (28 analyses). One larger grain is zoned from Fe# = 0.45, Cr# =0.52 to Fe# = 0.40, Cr# =0.57, and contains thin Al-rich lamellae not resolved by EMPA. One irregularly shaped patch of chromite included in olivine has Fe# =0.26 and contains no ZnO. Plagioclase laths are An ~53-60, with ≤0.01 wt.% K2O. Glass contains 75-76 wt% SiO2 and ~16 wt% Al2O3. The metal contains 5.2±0.2 wt% Ni, 0.46±0.02 wt.% Co, and 0.01±0.01 wt.% Cr, with Si and P below detection (168 analyses). Discussion: The olivine + chromite assemblage in TE 001 is similar to the most ferroan ureilites (Fo ~75-79 [2]), as are the oxygen isotopes [1]. The presence of a carbon phase supports this, although the identity of this phase (graphite as in ureilites?) remains to be determined. The “honeycomb” textured areas, in particular, the presence of olivine “reduction rims,” resemble shock-smelted olivine areas in ureilites [3], but interstitial melt-textured plagioclase laths + glass like those in TE 001 have not been reported in such (or any) ureilites. Olivine in TE 001 is marginally more ferroan than in the most FeO-rich ureilite, with Fe-Mg-Mn composition offset from the trend of olivine + low-Ca pyroxene ureilites similar to augite-bearing ureilites [4]. CaO and Cr2O3 contents are in the range of those in ureilite olivine [ ] , though Cr2O3 is at the extreme low end of the range [5]. Chromites (except the unusual one) have similar Fe# to the most ferroan primary chromites in ureilites [2], but distinctly lower Cr# (0.52 vs. 0.71). Metal compositions are with the range for metal in ureilites [7]. The absence of pyroxene and sulfide, and the high abundance of metal in TE 001, are unlike ureilites. One possibility is that a ferroan, chromite-bearing, pyroxene-poor ureilite was invaded (possibly due to impact) by a metallic liquid (low S content suggests very high temperature), resulting in complete melting of pyroxene and smelting of olivine, with rapid recrystallization of melted silicate as plagioclase + glass. Alternatively, a pre-existing metal-rich ureilite assemblage may have been impact melted. Additional types of data will be obtained to evaluate these hypotheses (i.e., is the metal indigenous?) and assess affinity to ureilites.

olivine↗