Search NASA⌕ Search

SEARCH · Search NASA

Results for “Rare Isotopes”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Rare gases and Ca, Sr, and Ba in Apollo 17 drill-core fines

Trapped gas isotopic compositions and spallation gas concentrations as functions of depth in the Apollo 17 drill core were determined from mass spectrometer studies by means of correlation techniques. The distribution of He, Ne, Ar, Kr, and Xe as well as Ca, Sr, and Ba was investigated, and rare-gas spallation and neutron capture profiles are compared with attention to proposed depositional models for the Taurus-Littrow regolith. The data exclude a sedimentation pattern similar to that found at the Apollo 15 site but are possibly compatible with long-term continuous accretion models or models of very recent rapid accumulation of regolith.

Pepin, R. O.↗
NASA NTRS1976

Volatile element depletion and K-39/K-41 fractionation in lunar soils

Evidence for selective loss and isotopic fractionation (in the case of K) of volatile elements during formation of agglutinates by micrometeoritic bombardment of lunar soils is presented. Concentrations and isotopic compositions of volatile elements (K, Rb, Pb) and nonvolatile elements (U, Th, Ba, Sr, rare earths) in separates taken from soils 14163, 14259, 15041, 68501, and 71500 are examined. Rayleigh fractionation calculations applied to K-39/K-41 isotopic data indicate ten-fold recycling of bulk soil, to account for observed isotopic anomalies. The lunar soil fines fraction seems to be a site of deposition for volatile or labile Pb produced during agglutination. Local fines (below 75 microns) are viewed as representative of the parent material for agglutinates formed in situ by micrometeoritic impact. Magnetic separation of agglutinates from soil 68501 revealed a bimodal population, with one class comprising welded blocky magnetic glasses.

Church, S. E.↗
NASA NTRS1991

Evidence for extreme mantle fractionation in early Archaean ultramafic rocks from northern Labrador

Samarium-neodymium isotope data for tectonically interleaved fragments of lithospheric mantle and meta-komatiite from the North Atlantic craton provide the first direct record of mantle differentiation before 3,800 Myr ago. The results confirm the magnitude of light-rare-earth-element depletion in the early mantle, and also its depleted neodymium isotope composition. The mantle fragments were able to retain these ancient geochemical signatures by virtue of having been tectonically incorporated in buoyant felsic crust, thus escaping recycling and homogenization by mantle convection.

Collerson, Kenneth D.↗
NASA NTRS2002

Enantiomeric and Isotopic Analysis of Sugar Derivatives in Carbonaceous Meteorites

Several classes of organic compounds are found in carbonaceous meteorites including amino acids, carboxylic acids, hydroxy acids, purines, and pyrimidines. Such compounds are thought to have been delivered to the early Earth in asteroids and comets and may have played a role in the origin of life. Likewise, sugar derivatives are critical to all known lifeforms. Recent analyses of the Murchison and Murray carbonaceous meteorites revealed a diverse suite of such derivatives, i.e., sugar alcohols, and sugar acids. This presentation will focus primarily on the analysis of individual sugar acids - their enantiomeric and isotopic composition. Analysis of these compounds may reveal the nature of past (or present) meteoritic sugars themselves. For example, if parent sugars decomposed (by well-known mechanisms) to give the present acids, were their enantiomeric ratios preserved? Combined with other evidence, the enantiomeric composition of such compounds as glyceric acid and (especially) rare acids may help to answer such questions. C-13 and D isotope analysis of meteoritic sugar alcohols (glycerol, threitol, ribitol, etc.) as a group revealed that they were indigenous to the meteorite. Preliminary C-13 analysis of glyceric acid shows that it is also extraterrestrial.

Cooper, George↗
NASA NTRS2011

Sm-Nd Isotopic Studies of Ureilite Novo Urei

Ureilites are ultramafic (harzburgitic) achondrites composed predominantly of olivine and pyroxenes, abundant carbon (graphites and shock-produced diamonds), some metal and sulfides. These rocks probably represent ultramafic mantles of differentiated parent asteroidal bodies. Age determinations of these rocks by Rb-Sr and Sm-Nd methods have been difficult because of their extremely low abundances of these parent-daughter elements. Nevertheless, Sm-Nd isochron ages were reported for Kenna, Goalpara, MET 78008 and PCA 82506 yielding ages of 3.74+/-0.02 Ga, approx.3.7 Ga, 4.09+/-0.08 Ga, 4.23+/-0.06 Ga, respectively [1-4]. These "young" Sm-Nd ages may represent secondary metasomatism events [1] related to impacts [5], as indicated by the similarly young Ar-39-Ar-40 degassing ages of 3.3-4.1 Ga for ureilites Kenna, Novo Urei and Havero [6]. Alternatively, it has been suggested that these rocks may have been contaminated with terrestrial crustal materials and the isochrons do not have any age significance [2,7]. Indications of old approx.4.56 Ga ages for ureilites were reported from the U-Pb and Sm-Nd model ages for MET 78008 [8]. More reliable evidences for old formation ages of ureilites were reported recently using the short-lived chronometers Hf-182-W-182, Al-26-Mg-26 and Mn-53-Cr-53. The deficits of 182W in ureilites suggest the metal-silicate segregation occurred very early, approx.1-2 Ma after CAI [9]. The Al-26-Mg-26 and Mn-53-Cr-53 studies for a feldspathic lithology [10] and the Mn-53-Cr-53 for olivine- and pyroxene-dominant lithologies [11] in ureilites revealed that they crystallized approx.5.4 Ma after CAI, i.e., at 4563.8+/-0.5 Ma relative to D.Orbigny. In this report, we present Sm-Nd isotopic data for a relatively fresh ureilite, Novo Urei, a rare ureilite fall (1886). We compare these data to Sm-Nd data for other ureilites, and discuss Novo Urei's petrogenesis

Shih, C.-Y.↗
NASA NTRS2015

On Infrared Excesses Associated with Li-Rich K Giants

Infrared (IR) excesses around K-type red giants (RGs) have previously been discovered using Infrared Astronomy Satellite (IRAS) data, and past studies have suggested a link between RGs with overabundant lithium and IR excesses, implying the ejection of circumstellar shells or disks. We revisit the question of IR excesses around RGs using higher spatial resolution IR data, primarily from the Wide-field Infrared Survey Explorer. Our goal was to elucidate the link between three unusual RG properties: fast rotation, enriched lithium, and IR excess. Our sample of RGs includes those with previous IR detections, a sample with well-defined rotation and lithium abundance measurements with no previous IR measurements, and a large sample of RGs asserted to be lithium-rich in the literature; we have 316 targets thought to be K giants, about 40% of which we take to be Li-rich. In 24 cases with previous detections of IR excess at low spatial resolution, we believe that source confusion is playing a role, in that either (a) the source that is bright in the optical is not responsible for the IR flux, or (b) there is more than one source responsible for the IR flux as measured in IRAS. We looked for IR excesses in the remaining sources, identifying 28 that have significant IR excesses by approximately 20 micrometers (with possible excesses for 2 additional sources). There appears to be an intriguing correlation in that the largest IR excesses are all in Li-rich K giants, though very few lithium-rich K giants have IR excesses (large or small). These largest IR excesses also tend to be found in the fastest rotators. There is no correlation of IR excess with the carbon isotopic ratio, 12C/13C. IR excesses by 20 micrometers, though relatively rare, are at least twice as common among our sample of lithium-rich K giants. If dust shell production is a common by-product of Li enrichment mechanisms, these observations suggest that the IR excess stage is very short-lived, which is supported by theoretical calculations. Conversely, the lithium-enrichment mechanism may only occasionally produce dust, and an additional parameter (e.g., rotation) may control whether or not a shell is ejected.

Li-rich↗
NASA NTRS1993

Magnesian anorthosites from the western highlands of the Moon: Isotope geochemistry and petrogenesis

Breccias from the Apollo 14 landing site have provided a wealth of information on the genesis of the lunar highlands. Various pristine rock-types have been discovered in relative abundance including rare ferroan anorthosites and alkali-suite and magnesian-suite rocks. Mineral-chemical and radiogenic isotopic data are reported here for a newly discovered Mg-suite anorthosite from Apollo 14, sample 14303,347. Meyer et al. reported U-Pb zircon analyses of Mg-suite highlands rocks from the western limb of the Moon. We have compiled these ages and generated a weighted average age of 4211 = 6 Ma; some 200 Ma younger than ferroan anorthosites. Utilizing this age for Mg-anorthosite 14303,347, our data results in an initial epsilon(sub Nd) value of -1.0 and initial Sr-87/Sr-86 of 0.69915. Based on trace-element, isotopic, and mineral-chemical data, the western highlands Mg-suite is interpreted to be crustal precipitates of a picritic magma, which assimilated KREEPy trapped liquid from upper-mantle cumulates during its transport to the crust.

Snyder, Gregory A.↗
NASA NTRS1979

The Sr and Nd isotopic record of Apollo 12 basalts - Implications for lunar geochemical evolution

Alkali, alkaline earth, and rare earth element data are reported for several Apollo 12 basalts which are representative of the four Apollo 12 magma types. Results confirm the heterogeneity of the lunar mantle and show that the Sm/Nd ratio of at least the Apollo 12 ilmenite basalts was decreased by 13-24% during magma genesis. In addition, whole mare basalt Sm-Nd data are not collinear on an isochron diagram; thus it is no longer possible to explain these data via mixing of 'primitive material' and 'early differentiates' as in the hybridization and assimilation models.

Nyquist, L. E.↗
NASA NTRS1972

On the origins of trapped helium, neon and argon isotopic variations in meteorites. I - Gas-rich meteorites, lunar soil and breccia. II - Carbonaceous meteorites.

Data are presented from stepwise heating experiments and total extractions on five meteorites: Kapoeta, Fayetteville, Holman Island, Cee Vee, and Pultusk. These data reveal the presence of four isotopically distinct trapped neon components. A comparison of trapped neon with trapped helium and argon in bulk analyses indicates the existence of correlated helium, neon and argon isotopic structures. Component B is attributed primarily to direct implantation of rare gas ions by the present day solar wind. Component C is identified with directly implanted low energy (1-10 Mev/n) solar flare rare gases. Component D is associated with rare gas ions implanted in meteoritic material by the primitive, pre-main sequence, solar wind. A fourth component, observed only in Kapoeta and the lunar fines and breccia, is tentatively attributed to parent body 'atmospheric' ions implanted in surface material by a solar wind induced electric field.

Black, D. C.↗
NASA NTRS1971

Partitioning of Eu and Sr between coexisting plagioclase and K-feldspar.

Minerals were separated by an EM approach and with the aid of liquids of great density. An analysis of K, Rb, Ca, Sr, Ha, and rare earth elements was conducted by means of a mass spectrometer isotope dilution technique. The behavior of the divalent europium ions during the partition process was found to be very similar to that of divalent strontium ions, taking into consideration data of the partition coefficients between coexisting feldspars in acidic rocks.

Nagasawa, H.↗
NASA NTRSDate not supplied

Outer Solar System Carbon in the Laboratory

Samples of outer solar system carbon in various forms are available for analysis in the laboratory. The Stardust Mission returned organics and a few carbonate grains from Jupiter Class comet Wild-2 [1]. These complement similar phases available in chondritic interplanetary dust particles, some of which derive from comets, although it is not definitively known which have that origin. Carbonaceous chondrites probably derive from C-complex asteroids which may have outer solar system origins, though this origin is model dependent. There are rare carbonaceous xenoliths in, principally, ordinary chondrites and ureilites whose bulk isotopic and bulk chemical compositions suggest an origin farther from the Sun that the remainder of carbonaceous chondrites [2,3]. These contain abundant carbonaceous materials, including organic-bearing aqueous fluid inclusions [4]. The Hayabusa2 spacecraft recently returned samples of C-class asteroid Ryugu to Earth, now being analyzed in labs worldwide. These materials are expected to be dominated by materials similar to C1 and C2 carbonaceous chondrites [5].

Michael Zolensky↗
NASA NTRS2024

The Potassium Isotope Composition of Aggregate Material From Asteroid Bennu

NASA’s OSIRIS-REx mission re-turned material from asteroid Bennu on September 24, 2023, marking the first time a U.S. mission has delivered asteroid samples to Earth, and the largest asteroid sample return to date. Due to the pristine nature of these primitive carbonaceous-rich samples, they allow us a rare opportunity to study our solar system’s formation to a degree not previously possible. Isotopes of moderately volatile elements (MVEs) have been recently developed as robust tracers for tracking different volatilization events within our Solar System. Of the MVEs, K has gained significant interest in recent years due to its ideal chemical and physical properties combined with technique improvements. Due to this, several recent studies have investigated the K isotope systematics within bulk chondrites and found an isotopic dichotomy be-tween the carbonaceous and non-carbonaceous chondrites (Figure 1), likely reflecting their different reservoirs which formed in the inner and outer protoplanetary disk respectively. Furthermore, systematic K isotope variations across the different carbonaceous chondrite groups and correlations with mass independent isotope systems such as Cr, Ti, and Ni, have also been observed. As a result, establishing the K isotope composition of bulk Bennu can be used to test the mission hypothesis that “Bennu’s parent asteroid accreted in the outer protoplanetary disk, beyond Jupiter, as recorded by distinct isotopic anomalies in a variety of elements” . In addition to early solar system processes, K isotopes can also be fractionated by space weathering as shown by comparisons between mature and immature lunar regolith. The degree of K isotope fractionation caused by space weathering correlates with the regolith maturity index and is an order of magnitude larger than what is observed in bulk meteorite samples which have not undergone strong space weathering processes. As such, the K isotope systematics of Bennu samples could provide an independent assessment of regolith maturity of the asteroid surface, helping to directly test the mission hypothesis that “Space weathering changed the chemistry and mineralogy of optically active surfaces” . In order to test both this hypothesis, and the hypothesis relating to Bennu’s accretion location, we aim to conduct high-precision K isotope analysis on bulk Bennu aggregates.

K Wang↗
NASA NTRS1991

Cosmic dust: Laboratory analyses of extremely small particles

A discussion of cosmic dust, its classification, the usefulness of its analysis, and problems associated with its analysis is presented. All measurements on stratospheric dust particles presented here were made with secondary ion mass spectrometry (SIMS). The SIMS technique turns out to be an extremely useful tool in the study of very small particles and made a number of firsts possible. The isotopic composition of cosmic dust particles were measured for the first time. It was also the first time that it was possible to measure the abundances of the rare earth elements in these particles. However, the most important advance this work represents is that both trace elemental and isotopic abundances were successfully measured in the same particles. Thus, for the first time, it is possible to compare isotopic and trace element abundance data of the same cosmic dust particles.

Stadermann, Frank J.↗
NASA NTRS1977

Rare earth and trace element geochemistry of a fragment of Jurassic seafloor, Point Sal, California

Rocks from an ophiolite suite once on the seafloor were analyzed for rare earth elements (REE), Sc, Co, Na2O, Cr, Zn and FeO. Strontium isotope exchange noted in some of the lavas is attributed to basalt-seawater interaction; the Ce abundance in smectite- and zeolite-bearing lavas may also be due to prolonged exposure to seawater. The higher grades of metamorphic rock, however, show no variation from the usual flat or slightly light REE depleted profiles. Plutonic igneous rock, all light REE depleted, have total REE abundances varying by a factor of 100 between the dunites and diorites. In order of decreasing REE abundance are hornblende, clinopyroxene, plagioclase, orthopyroxene and olivine. Calculations of REE contents of liquids in equilibrium with early cumulative clinopyroxenes suggest that the parent to the stratiform sequence was more depleted in light REE than the parent to the lava pile.

Menzies, M.↗
NASA NTRS2006

Formation of Metal and Silicate Globules in Gujba: A New Bencubbin-like Meteorite Fall

Gujba is a coarse-grained meteorite fall composed of 41 vol% large kamacite globules, 20 vol% large light-colored silicate globules with cryptocrystalline, barred pyroxene and barred olivine textures, 39 vol% dark-colored, silicate-rich matrix, and rare refractory inclusions. Gujba resembles Bencubbin and Weatherford in texture, oxygen-isotopic composition and in having high bulk delta N-15 values (approximately +685%0). The He-3 cosmic-ray exposure age of Gujba (26 +/- 7 Ma) is essentially identical to that of Bencubbin, suggesting that they were both reduced to meter-size fragments in the same parent-body collision. The Gujba metal globules exhibit metal-troilite quench textures and vary in their abundances of troilite and volatile siderophile elements. We suggest that the metal globules formed as liquid droplets either via condensation in an impact-generated vapor plume or by evaporation of preexisting metal particles in a plume. The lower the abundance of volatile elements in the metal globules, the higher the globule quench temperature. We infer that the large silicate globules also formed from completely molten droplets; their low volatile-element abundances indicate that they also formed at high temperatures, probably by processes analogous to those that formed the metal globules. The coarse-grained Bencubbin-Weatherford-Gujba meteorites may represent a depositional component from the vapor cloud enriched in coarse and dense particles. A second class of Bencubbin-like meteorites (represented by Hammadah a1 Hamra 237 and QUE 94411) may be a finer fraction derived from the same vapor cloud

Rubin, Alan E.↗
NASA NTRS1981

Spallogenic rare gases in iron meteorites with anomalous silver

He, Ne, and Ar have been measured in seven iron meteorites for which anomalous Ag isotopic compositions were reported, in order to determine if Ag-107 excesses could be related to galactic cosmic-ray bombardment of these meteorites. The results show that no correlation exists between Ag-107 excess and either the fluence or the energy spectrum of the particles producing spallogenic rare gases. Cosmic-ray-produced Ag-107 estimated from Ar-38 concentrations can account for only about 1 percent of the observed excess. Elimination of cosmic-ray bombardment as a production mechanism for Ag-107 excess strengthens the conclusion that the excess Ag-107 is the decay product of short-lived Pd-107 (half life 6.5 million years). The iron meteorite Pinon is shown to contain trapped rare gases with He-4/Ne-20 approximately 600.

Villa, I. M.↗