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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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188 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Grossite-Rich Refractory Inclusions in Carbonaceous Chondrites: Evidence for Early Generation of Different O-Isotope Reservoirs in the Protoplanetary Disk and O-Isotope Exchange During Fluid-Rock Interaction

The oxygen isotopic composition of the Sun inferred from the measurements of the solar wind returned by the Genesis spacecraft is O-16-enriched (△O-17 = -28.4±3.6‰) relative to the whole-rock O-isotope compositions of chondrites and achondrites, and chondrule phenocrysts, which all plot close to the terrestrial fractionation line (△O-17 ∼ ±5‰). Vast majority of refractory inclusions (CAIs and AOAs) in carbonaceous chondrites of petrologic types 2-3.0 are iso-topically uniform and have solar-like △O-17. In contrast, CAIs and AOAs in metamorphosed CV and CO chondrites are isotopically heterogeneous with melilite, anorthite, perovskite, Zr- and Sc-rich oxides and silicates, and occasionally Al, Ti-diopside being O-16-depleted relative to hibonite, spinel, Al-diopside, and forsterite. The timing of generation of different O-isotope reservoirs and the nature of O-isotope heterogeneity in refractory inclusions in CO3 and CV3 chondrites are poorly known. Grossite (CaAl4O7) is one of the first minerals predicted to condense from a gas of solar composition and therefore it could have recorded isotopic compositions of reservoirs during the earliest stages of the Solar System evolution. Here we report on O-isotope compositions of grossite-rich CAIs in CH3 and CO3 chondrites measured in situ with the UH Cameca ims-1280. For analytical procedures see [9].

A N Krot↗
NASA NTRS2023

New Insights Into Aristarchus Crater With LRO LAMP Far-Ultraviolet Observations

Aristarchus crater is a Copernican-age impact crater well known for its high-albedo ejecta blanket and nearby flow features rich in pyroclastic materials. The Lyman Alpha Mapping Project (LAMP) is a far-ultraviolet (FUV) spectrograph (57–197 nm) on board the Lunar Reconnaissance Orbiter (LRO). LAMP data identified Aristarchus crater as having a high Off-band (155–184 nm) to On-band (130–155 nm) albedo (Off/On) ratio, providing new insight into the mineral composition of the area. Previous LAMP observations of bright crater rays and lunar swirls show that regions of high Off/On-band ratios may indicate highly feldspathic compositions. In this study we use LAMP data to understand FUV compositional signatures at Aristarchus. We investigate four well-characterized regions of interest around Aristarchus crater, and we compare Off/On-band ratios at Aristarchus crater to laboratory-derived ratios of several endmembers such as anorthite and olivine. We further analyze LAMP FUV spectra alongside near-infrared spectra from the Moon Mineral Mapper (M3) on board Chandrayaan-1 to characterize the mineralogy in several regions of interest. We find that LAMP Off/On-band ratios are able to distinguish between plagioclase feldspars and minerals such as quartz and mafic-dominated compositions. The LAMP Off/On-band ratios at Aristarchus are higher than previously reported ratios for plagioclase-rich regions, suggesting that the composition is unique to Aristarchus. Spectra from LAMP and M 3 both show that the central peak and high-albedo ejecta around Aristarchus contain shocked, possibly alkalic, plagioclase feldspar.

Elizabeth Czajka↗
NASA NTRS2024

Understanding Mercury’s Magmatic History: Geochemical Affinity, Compatibility, & Volatility Changes Due to Reduction

Mercury’s depletion in O and abundance of S substituting in as S2- has fundamental effects on the physicochemical properties of minerals and melts because O2- is the dominant rock-forming anion. These changes exert a first order effect on planetary body evolution, including the initial distribution of elements, crystallization paths, stability of phases, and mineral chemistry. Experimental and empirical data have revealed that most nominally lithophile elements become more chalcophile and/or siderophile at reducing conditions, which can be visualized through a re-interpreted Goldschmidt classification table prepared for McCubbin & Anzures’s Treatises of Geochemistry 3rd edition chapter under review. Additionally, the S bonding environment influences Mercurian phase equilibria by decreasing the stability of forsterite and anorthite while increasing the stability of enstatite, silica, and albite through re-projection of silicate ternaries.

Brendan Anthony Anzures↗
NASA NTRS2024

Ternary Feldspar Within Felste Clasts From Apollo Impact Melt Breccia 72255

Granitic clasts with unique ternary feldspar compositions have been identified within samples of the layered impact melt breccia from Apollo 17 Station 2 Boulder 1 (72215, 72235, 72255 and 72275), and in a felsite clast from station 3 (73215). These “ternary” compositions seemingly plot within the miscibility gap of the albite-anorthite-orthoclase (Ab-An-Or) system. Feldspars with these compositions have not been identified in terrestrial samples, and equilibrium feldspar compositions from laboratory experiments indicate they would not be thermodynamically stable. Thus, the physiochemical processes involved in forming these unique ternary feldspars remain poorly understood. To better constrain the formation of ternary feldspar within lunar breccias, we have undertaken a coordinated scanning electron microscope (SEM)-based coupled electron backscatter diffraction (EBSD) and energy dispersive spectrometry (EDS), electron microprobe analyzer (EPMA) wavelength dispersive spectrometry, and transmission electron microscopy (TEM) study. The goals of this study are twofold: 1) confirm whether ternary feldspar is present as coherent, single-crystals or sub-microscopic intergrowths of normal compositions, and 2) better constrain the formation conditions of clasts containing ternary feldspar.

T. M. Erickson↗
NASA NTRSDate not supplied

Anhydrous Primary Minerals in Ryugu, Ivuna, and Bennu

Samples returned from asteroid Ryugu are chemically and mineralogically similar to CI chondrites [e.g., 1–3]. Both are predominantly composed of low-temperature aqueously formed secondary minerals, whereas high-temperature anhydrous primary minerals, such as olivine, low-Ca pyroxene, spinel, and hibonite, are rarely present. Using secondary ion mass spectrometry (SIMS; Cameca ims-1280HR at Hokkaido University), we performed O [4] and Al–Mg [5] isotope measurements of anhydrous primary minerals in samples of Ryugu and the Ivuna CI chondrite to constrain their origin.Anhydrous primary minerals in our samples of Ryugu and Ivuna occur mostly as monomineralic isolated grains embedded in hydrated matrix. Their O-isotope compositions are distributed along the slope-1 line on the O three-isotope diagram and range from Δ17O ~ –23 to 0‰. Mg-Al spinel grains are 16O-rich (Δ17O ~ –23‰). Low-Ca pyroxene grains are 16O-poor (Δ17O ~ –5‰). Olivine grains show a bimodal distribution of O-isotope composition:10 of 34 grains measured are 16O-rich (Δ17O ~ –23‰) and 24 grains are 16O-poor (Δ17O ~ –7 to 0‰). We found refractory inclusions composed of Mg-Al spinel and hibonite, one from Ryugu and one from Ivuna. Also, in Ivuna, we found an amoeboid olivine aggregate ( AOA) composed of olivine, diopside, anorthite, and Mg-Al spinel and an inclusion composed of olivine and Mg-Al spinel. The minerals in all of these inclusions are 16O-rich (Δ17O ~ –24‰).The 16O-rich grains and inclusions are mineralogically and O-isotopically similar to calcium-aluminum–rich inclusions (CAIs) and AOAs reported in other carbonaceous chondrites [6, 7]. In addition, the initial 26Al/27Al ratios of the two spinel-hibonite inclusions are inferred as ~4.4 × 10–5, also similar to most CAIs in carbonaceous chondrites [6, 8]. The range of Δ17O values for the 16O-poor olivine and low-Ca pyroxene grains is consistent withthat of these minerals in chondrules in most carbonaceous chondrites [9]. Moreover, the most frequent Δ17O value (–6‰) for Mg-rich (Mg# > 97) olivine grains is identical to those for chondrules. Although CI chondrites and Ryugu samples are devoid of chondrules, the 16O-poor grains most likely represent fragments of chondrule-like objects. The presence of both 16O-poor chondrule-like and 16O-rich refractory inclusion–like minerals in Ryugu and Ivuna suggests that some of their building blocks are similar to those of other carbonaceous chondrite groups. They both probably formed in the inner solar protoplanetary disk and were subsequently transported outward.Preliminary data for petrography of asteroid Bennu samples and chemical and isotopic compositions of theiranhydrous primary minerals will also be presented in the meeting.

N Kawasaki↗
DOE OSTI2022

Corrosion-Resistant Plug Materials for Geothermal Well Fluid Control

Conventional cements and plugs are challenged by corrosion in CO 2 -rich and extreme geothermal environments, due to the hostile chemistry and high temperatures. Thermite-based sealing and well intervention technologies are being applied in the oil and gas industry, combining the energy delivery capability of thermite materials with the sealing characteristics of low melt temperature alloys. The thermite reaction products (ceramics) and the sealing alloys used in these plugs both have very attractive corrosion properties, and their operating envelopes extend into geothermal conditions. Thermite plugs and platforms, without supplemental sealing materials, have been considered for nuclear waste isolation, carbon sequestration, and geothermal applications due to the geochemical stability of the ceramic product and its very high service temperature. This study addresses corrosion resistance of the thermite reaction products. A range of engineered thermite systems which yield thermite reaction products including pure aluminum oxide, feldspar, or aluminosilicate solid solutions (in addition to the iron produced in thermite reactions) was developed. These materials were evaluated for their strong acid resistance (pH 1), carbonate resistance (sodium carbonate) and thermal shock resistance (600 °C heating → cold water quenching repeated three times). Performance of different materials was evaluated based on the changes in mechanical properties, water-fillable porosity, phase changes under stress conditions. The aluminosilicate product exhibited very good corrosion resistance, both from material loss and strength perspectives, while the other products performed with varying degrees of stability. This paper presents the results of the thermite corrosion studies and describes the novel tools being deployed, and under development, to satisfy challenging barrier and intervention applications.

02 PETROLEUM↗