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NASA NTRS1985

Early evolution of the crust-mantle system

Nd isotopic data indicate that most Archean igneous rocks including compositions ranging from komatiite to tonalite are derived from undepleted or depleted upper mantle sources. If sampling is representative, only a few require enriched sources. A major unresolved question is the fate of the material removed from the upper mantle leaving early depleted sources as residue. One possibility is that widespread depletion of the early mantle resulted from a period of early degassing and magmatism. Rare gas isotopic data, in particular 129Xe/130Xe ratios, seem to demand that the upper mantle was extensively degassed at or before 4.4 b.y. and this led to rapid growth of the atmosphere and oceans. The lower mantle, however, was not significantly degassed during this event. It is likely that such widespread degassing and magmatism of the upper mantle transferred significant quantities of incompatible elements into the uppermost mantle or crust. Once formed, such an enriched fraction should resist recycling into the mantle and collect at or near the Earth's surface. One possibility is that it collects chiefly in a zone of partial melting, analogous to the present low-velocity zone at the base of the lithosphere.

Condie, K. C.↗

NASA NTRS2016

Spatial and Temporal Trends in Precambrian Nitrogen Cycling: A Mesoproterozoic Offshore Nitrate Minimum

Fixed nitrogen is an essential nutrient for eukaryotes. As N2 fixation and assimilation of nitrate are catalyzed by metalloenzymes, it has been hypothesized that in Mesoproterozoic oceans nitrate was limited in offshore environments by low trace metal concentrations and high rates of denitrification in anoxic and episodically euxinic deep water masses, restricting eukaryotes to near-shore environments and limiting their evolutionary innovation. To date this hypothesis has only been tested in the Belt Supergroup (∼1.4 Ga), with results that support an onshore-offshore nitrate gradient as a potential control on eukaryote ecology. Here we present bulk nitrogen and organic carbon isotopic data from non-isochronous cross-basinal facies across the Bangemall (∼1.5 Ga) and the Roper (∼1.4–1.5 Ga) basins to better understand the extent and variability of onshore-offshore nitrogen isotope gradients in the Mesoproterozoic. Both basins show an average ∼1-2‰ enrichment in δ-15N(sub bulk) from deep to shallow facies, with a maximum range from ~1‰ offshore to +7.5‰ onshore. Unlike the Belt basin, the Bangemall and Roper basins show some offshore δ-15N(sub bulk) values that are enriched beyond the isotopic range associated with biological N2 fixation alone. This suggests a mixture of aerobic and anaerobic metabolisms offshore. In shallow waters, where δ-15N(sub bulk) enrichment peaks, an aerobic nitrogen cycle was evidently operating. Even though isotopic signatures of aerobic nitrogen cycling are seen in all parts of the Bangemall and Roper basins, our data are consistent with a lateral gradient in nitrate availability within the photic zone, with higher concentrations in near-shore environments than offshore. The variability in δ-15N(sub bulk) values in each depositional environment and the consistently low δ-15N(sub bulk) values from Mesoproterozoic units compared to the Paleoproterozoic and Neoproterozoic suggest that nitrate concentrations in the global ocean were likely low. This trend is now seen in all three Mesoproterozoic basins so far examined, and contrasts with the Paleoproterozoic and Neoproterozoic where nearly all δ-15N(sub bulk) data plot above the N2 fixation window. Thus, we propose that the Mesoproterozoic ocean was characterized by a nitrate minimum, with the lowest concentrations in offshore environments. This inference is consistent with a Mesoproterozoic O2 decline following a temporary Paleoproterozoic O2 peak, and it further supports the idea that nitrate limitation offshore may have contributed to the restriction of photosynthetic eukaryotes to near-shore environments, delaying their rise to ecological dominance until the Neoproterozoic Era.

Mesoproterozoic↗

NASA NTRS1972

Radioactive heat sources in the lunar interior.

Published models for the moon's thermal history typically imply present day central temperatures far too high to be consistent with the recently proposed lunar temperature profile of Sonett et al. (1971). Furthermore, chemical data on Apollo samples show that the moon is depleted relative to chondrites in volatile elements, and possibly enriched relative to chondrites in refractory elements. Additional thermal models have therefore been investigated in order to set upper limits on lunar radioactivity consistent with the proposed temperature distribution. For an initially cold, uniform moon, devoid of potassium, a maximum uranium content of 23 parts per billion is inferred.

Hays, J. F.↗

NASA NTRS1981

Isotopic variations in primitive meteorites

Oxygen isotopic variations in carbonaceous chondrites and ordinary chondrites can each be interpreted as mixtures of two isotopically different reservoirs, one consisting of solids, enriched in O-16, the other of a gas, depleted in O-16 relative to terrestrial abundances. The data indicate a common source of the solids for each of the two classes of meteorites, but a different gas reservoir for each. These conditions might obtain in gaseous protoplanets. It is noted that radiogenic Mg-26 is variable in abundance among some classes of Allende inclusions, implying either nebular heterogeneity with respect to Al-26/Al-27 ratios or time differences of crystal formation. The presence of excess Ag-107 from decay of extinct Pd-107 corroborates the evidence from Mg-26 for a time interval of at most a few million years between the last nucleosynthetic event and the accretion of substantial bodies in the solar system.

Clayton, R. N.↗

NASA NTRS1988

Geochemistry of amphibolites from the Kolar Schist Belt

How the Nd isotope data suggest that the amphibolites from the schist belt were derived from long-term depleted mantle sources at about 2.7 Ga is described. Trace element and Pb isotope data from the amphibolites also suggest that the sources for the amphibolites on the western and eastern sides of the narrow schist belt were derived from different sources. The Pb data from one outcrop of the central tholeiitic amphibolites lies on a 2.7 Ga isochron with a low model. The other amphibolites (W komatiitic, E komatiitic, and E tholeiitic) do not define isochrons, but suggest that they were derived from sources with distinct histories of U/Pb. There is some suggestion that the E komatiitic amphibolites may have been contaminated by fluids carrying Pb from a long-term, high U/Pb source, such as the old granitic crust on the west side of the schist belt. This is consistent with published galena Pb isotope data from the ore lodes within the belt, which also show a history of long-term U/Pb enrichment.

Balakrishnan, S.↗

NASA NTRS1989

Morphology and compositional differentiation of the surface of comets

The spacecraft missions to Comet Halley gave us the first detailed view of a comet nucleus. What was suspected before, that the nucleus surface was heterogeneous, was confirmed. The Halley Multicolor Camera aboard Giotto recorded jet-like dust features emanating from active regions covering approximately 15 percent of the surface that were responsible for emitting most of the dust and gas. An intensity gradient across the nucleus originating at the active areas and falling off to the darker, inactive region on the night side is caused by small particles that are more easily entrained by surface winds than larger particles that tend to remain in the jets. Data from the PIA (Giotto) and PUMA (Vega 1,2) instruments indicate that the smallest dust particles are enriched with organics (CHON particles). Some of this fine dust gravitationally settles creating a thin surface layer rich in organics. Particularly strong dust jets may cause wind-blown surface structures over inactive areas, such as, leeward dust accumulation behind hills. At close heliocentric distances the fine dust may be sintered on the surface.

Huebner, W. F.↗

NASA NTRS2010

Thermal Infrared Emission Spectroscopy of Synthetic Allophane and its Potential Formation on Mars

Allophane is a poorly-crystalline, hydrous aluminosilicate with variable Si/Al ratios approx.0.5-1 and a metastable precursor of clay minerals. On Earth, it forms rapidly by aqueous alteration of volcanic glass under neutral to slightly acidic conditions [1]. Based on in situ chemical measurements and the identification of alteration phases [2-4], the Martian surface is interpreted to have been chemically weathered on local to regional scales. Chemical models of altered surfaces detected by the Mars Exploration Rover Spirit in Gusev crater suggest the presence of an allophane-like alteration product [3]. Thermal infrared (TIR) spectroscopy and spectral deconvolution models are primary tools for determining the mineralogy of the Martian surface [5]. Spectral models of data from the Thermal Emission Spectrometer (TES) indicate a global compositional dichotomy, where high latitudes tend to be enriched in a high-silica material [6,7], interpreted as high-silica, K-rich volcanic glass [6,8]. However, later interpretations proposed that the high-silica material may be an alteration product (such as amorphous silica, clay minerals, or allophane) and that high latitude surfaces are chemically weathered [9-11]. A TIR spectral library of pure minerals is available for the public [12], but it does not contain allophane spectra. The identification of allophane on the Martian surface would indicate high water activity at the time of its formation and would help constrain the aqueous alteration environment [13,14]. The addition of allophane to the spectral library is necessary to address the global compositional dichotomy. In this study, we characterize a synthetic allophane by IR spectroscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM) to create an IR emission spectrum of pure allophane for the Mars science community to use in Martian spectral models.

Rampe, E. B.↗

NASA NTRS2012

Derivation of Apollo 14 High-Al Basalts at Discrete Times: Rb-Sr Isotopic Constraints

Pristine Apollo 14 (A-14) high-Al basalts represent the oldest volcanic deposits returned from the Moon [1,2] and are relatively enriched in Al2O3 (>11 wt%) compared to other mare basalts (7-11 wt%). Literature Rb-Sr isotopic data suggest there are at least three different eruption episodes for the A-14 high-Al basalts spanning the age range approx.4.3 Ga to approx.3.95 Ga [1,3]. Therefore, the high-Al basalts may record lunar mantle evolution between the formation of lunar crust (approx.4.4 Ga) and the main basin-filling mare volcanism (<3.85 Ga) [4]. The high-Al basalts were originally classified into five compositional groups [5,6], and then regrouped into three with a possible fourth comprising 14072 based on the whole-rock incompatible trace element (ITE) ratios and Rb-Sr radiometric ages [7]. However, Rb-Sr ages of these basalts from different laboratories may not be consistent with each other because of the use of different 87Rb decay constants [8] and different isochron derivation methods over the last four decades. This study involved a literature search for Rb-Sr isotopic data previously reported for the high-Al basalts. With the re-calculated Rb-Sr radiometric ages, eruption episodes of A-14 high-Al basalts were determined, and their petrogenesis was investigated in light of the "new" Rb-Sr isotopic data and published trace element abundances of these basalts.

Hui. Hejiu↗

NASA NTRS2015

Water Distribution in the Continental and Oceanic Upper Mantle

Nominally anhydrous minerals such as olivine, pyroxene and garnet can accommodate tens to hundreds of ppm H2O in the form of hydrogen bonded to structural oxygen in lattice defects. Although in seemingly small amounts, this water can significantly alter chemical and physical properties of the minerals and rocks. Water in particular can modify their rheological properties and its distribution in the mantle derives from melting and metasomatic processes and lithology repartition (pyroxenite vs peridotite). These effects will be examined here using Fourier transform infrared spectrometry (FTIR) water analyses on minerals from mantle xenoliths from cratons, plume-influenced cratons and oceanic settings. In particular, our results on xenoliths from three different cratons will be compared. Each craton has a different water distribution and only the mantle root of Kaapvaal has evidence for dry olivine at its base. This challenges the link between olivine water content and survival of Archean cratonic mantle, and questions whether xenoliths are representative of the whole cratonic mantle. We will also present our latest data on Hawaii and Tanzanian craton xenoliths which both suggest the intriguing result that mantle lithosphere is not enriched in water when it interacts with melts from deep mantle upwellings (plumes).

Peslier, Anne H.↗

NASA NTRS1988

Noble metals in mid-ocean ridge volcanism: A significant fractionation of gold with respect to platinum group metals

Hydrothermal precipitates, black smoker particulate, and massive sulphide dredge samples from the Explorer Ridge on the Juan de Fuca Plate and the TAG hydrothermal area on the Mid-Atlantic Ridge were analyzed for selected noble metals including Au, Ir and Pd by radiochemical neutron activation analysis. The preliminary results indicate that gold contents may reach the ppm range although values in the neighborhood of 100 to 200 ppb are more typical. The platinum group elements (PGE) represented by Ir and Pd are typically less than 0.02 ppb and less than 2 ppb respectively. These abundances represent a significant enrichment of gold relative to the PGE in comparison with average noble metal abundances in mid-ocean ridge basalts (MORB). A partial explanation of this distinctive fractionation can be found in the concepts of sulfur-saturation of basic magma in mid-ocean ridge (MOR) settings, and the origin of MOR hydrothermal fluids. Experimental and petrological data suggest that MORBs are sulfur-saturated at the time of magma generation and that an immiscible sulfide component remains in the mantle residue. Hence, MORBs are noble metal-poor, particularly with respect to PGE. Consequently, black smoker fluids can be expected to reflect the low Ir and Pd contents of the rock column. The average Au content of MORB is 1.3 ppb, and so the rock column is not significantly enriched in Au. The generation of fluids which precipitate solids with 200 ppb Au is apparently dependent on highly efficient fluid chemistry to mobilize Au from the rock column, high Au solubility in seawater hydrothermal fluids and efficient precipitation mechanisms to coprecipitate Au on Fe, Zn and Cu sulfides. Significant differences in these parameters appear to be the ultimate cause of the strong Au-PGE fractionation in the MOR setting. It does not appear from the current data base that MOR hydrothermal fluids are significant contributors to the Ir enrichment seen in Cretaceous-Tertiary boundary sediments.

Crocket, James H.↗

NASA NTRSDate not supplied

MULTI-OMICS STUDY OF THE EFFECT OF REDOX-ACTIVE METALLOPORPHYRIN ON MURINE RETINA DURING SPACEFLIGHT

Astronauts returning from spaceflight have experienced eye problems, which may decrease retinal performance and lead to long-term effects on visual acuity. This study leverages the collected data from spaceflown murine retinas that were treated with redox-active metalloporphyrin (BuOE) to mitigate spaceflight-induced changes and respective ground controls. 10-week-old adult C57BL/6 male mice (n=5 in each of BuOE treated and saline control groups for spaceflown and ground control samples) were flown on Space-X 24 to the ISS national lab, kept in low earth orbit for 35 days and returned to Earth alive. Our multi-omics analysis of RNA-sequencing and reduced representation bisulfite sequencing (RRBS) data generated from subsequent murine retina tissues uncovered genes, pathways, and epigenetic modifications consistent with therapeutic potential of BuOE. From RNA-Seq analysis of spaceflown murine samples, the treatment group show differentially expressed genes relative to saline controls that reached significance (adjusted p-value < 0.05) and included genes Gpx3 and Crhbp, which are related to protection against cell oxidative damage and cellular response to organonitrogen compounds. Ranked fold-changes from the same contrast were used for gene set enrichment analysis, which showed biological processes reaching significance (adjusted p-value < 0.05) including glutathione metabolic processes and cellular response to xenobiotic stimulus. RRBS data of the spaceflown murine samples found 139 hyper or hypo differentially methylated sites spread across chromosomes 1-19 (20% promoters, 21% exons, 43% introns | 20 CpG islands, 7 CpG shores) with a 10% methylation difference (q-value < 0.05).The findings from this investigation have the potential to provide valuable insights into the molecular mechanisms underlying conditions like spaceflight associated neuro-ocular syndrome and assess the effectiveness of BuOE as a countermeasure for astronauts experiencing neuro-ophthalmic abnormalities, which can lead to long-term effects on visual acuity.

Biostatistics↗

NASA NTRS2024

Multi-Omics Study of the Effect of Redox-Active Metalloporphyrin on Murine Retina During Spaceflight

Biostatistics↗

NASA NTRS1994

Effect of Carbon Dioxide Enrichment on Radish Production Using Nutrient Film Technique (NFT)

Radish plants (Raphanus sativus L. cvs. Cherry Belle, Giant White Globe, and Early Scarlet Globe) were grown in four different CO2 enriched environments, 0.04, 0.10, 0.50, and 1.00 kPa (400, 1000, 5000, 10000 ppm). Cultivar responses to CO2 treatments varied, where cv. Cherry Belle showed no significant response to CO2 enrichment, cv. Giant White Globe was moderately affected and Early Scarlet Globe was strongly affected. Enrichment at 0.10 kPa led to greater root dry matter (DM) than 1.00 kPa for cv. Giant White Glove, whereas 0.10 kPa produced greater storage root, shoot, and root DM than 1.00 kPa for cv. Early Scarlet Globe. The data suggest that 1.00 kPa CO2 may be detrimental to the growth of certain radish cultivars. Root:shoot ratios tended to increase with increasing CO2 concentration. Water use efficiency (g biomass/kg H2O) increased with increasing CO2 enrichment, up to 0.5 kPa but then declined at the 1.00 kPa treatment. The total nitric acid used to maintain nutrient solution pH was lowest at the 1.00 kPa treatment as well, suggesting a decreased demand of nutrients by the plants at the highest CO2 level.

Mackowiak, C. L.↗

NASA NTRS1975

Air pollution source identification

The techniques available for source identification are reviewed: remote sensing, injected tracers, and pollutants themselves as tracers. The use of the large number of trace elements in the ambient airborne particulate matter as a practical means of identifying sources is discussed. Trace constituents are determined by sensitive, inexpensive, nondestructive, multielement analytical methods such as instrumental neutron activation and charged particle X-ray fluorescence. The application to a large data set of pairwise correlation, the more advanced pattern recognition-cluster analysis approach with and without training sets, enrichment factors, and pollutant concentration rose displays for each element is described. It is shown that elemental constituents are related to specific source types: earth crustal, automotive, metallurgical, and more specific industries. A field-ready source identification system based on time and wind direction resolved sampling is described.

Fordyce, J. S.↗

NASA NTRS1980

Fission xenon in troctolite 76535

Xenon released in stepwise heating of troctolite 76535 shows remarkable similarity to that from the gas-rich breccias. The low temperature fractions are highly enriched in fissiogenic xenon from Pu-244. Although the quantity of fission xenon is not inconsistent with reported age data, release patterns demonstrate that this component is not due to in situ decay. However, in contrast with the gas-rich breccias, the parentless radionuclear component in 76535 is not accompanied by solar wind xenon. Mechanisms for the emplacement of this component in 76535 cannot, therefore, involve exposure on the lunar surface but most likely involve adsorption along intergranular boundaries or thermally driven redistribution. The fact that xenon released from a gas-poor igneous cumulate can mimic that from gas-rich breccias, except for the presence of solar wind xenon in the latter, suggests that direct exposure to space is not required for the incorporation of these weakly bound, surface-correlated, parentless radionuclear components in lunar samples.

Hohenberg, C. M.↗

NASA NTRS1987

The effect of pressure and excitation energy on the isotopic fractionation in the formation of ozone by discharge of O2

Isotopic fractionation processes in the formation of O3 by discharge (at 20 kV and 3 MHz) of O2 in a fused silica container at 77 K are investigated experimentally, with a focus on the effects of changes in the isotopic abundances in the predischarge O2, the O2 pressure, and the excitation energy on the isotope abundances in the postdischarge O2 and O3. The results are presented in extensive tables and graphs and characterized in detail, and good general agreement is found with data obtained using 60-kHz excitation (Yang and Epstein, 1987). It is shown that O-17 and O-18 enrichment of the residual O2 (when the predischarge gas is enriched) or of the O3 (when atmospheric isotope abundances are used) can occur independently of one another. It is inferred that the rate of anharmonic predissociation of vibrationally hot O3 depends on the symmetry and mass of the O3 molecules. The significance of the present findings for studies of anomalous oxygen isotope abundances in meteorites is indicated.

Yang, Jongmann↗

NASA NTRS2005

The Martian Soil as a Geochemical Sink for Hydrothermally Altered Crustal Rocks and Mobile Elements: Implications of Early MER Results

Hydrothermal and aqueous alteration can explain some of the exciting results from the MER team s analyses of the martian soil, including the major elements, mobile elements, and the nickel enrichment. Published results from the five lander missions lead to the following conclusions: 1) The soil appears to be globally mixed and basaltic with only small local variations in chemistry. Relative to martian basaltic meteorites and Gusev rocks the soils are depleted in the fluid-mobile element calcium, but only slightly enriched to somewhat depleted in iron oxide. 2) The presence of olivine in the soils based on M ssbauer data argues that the soil is only partly weathered and is more akin to a lunar regolith than a terrestrial soil. 3) The presence of bromine along with sulfur and chlorine in the soils is consistent with addition of a mobile element component to the soil.

Newsom, H. E.↗

NASA NTRS1997

Smoldering News From STS-77 Endeavour

The Microgravity Smoldering Combustion (MSC) experiment lifted off aboard the Space Shuttle Endeavour for its second flight in May 1996, as part of the STS-77 mission. This experiment is part of a series of studies focused on the smolder characteristics of porous combustible materials in a microgravity environment. Smoldering is a nonflaming form of combustion that takes place in the interior of combustible materials. Common examples of smoldering are nonflaming embers, charcoal briquettes, and cigarettes. The objective of this study is to provide a better understanding of the controlling mechanisms of smoldering in microgravity and normal Earth gravity (1g). As with other forms of combustion, gravity affects the availability of air and transport of heat, and therefore, the rate of combustion. The results of the microgravity experiments will be compared with identical ones carried out in 1g. In addition, they will be used to verify present theories of smolder combustion and will provide new insights into the process of smoldering combustion, enhancing our fundamental understanding of this frequently encountered combustion process and guiding improvements in fire safety practices. Two smoldering combustion tests with polyurethane foam were successfully accomplished during the STS-77 mission. The tests investigated smoldering combustion in a quiescent (no-flow) enriched oxygen environment, and in an air environment with a 2-mm/sec airflow through the fuel sample. The primary data from the tests are the ignition characteristics, spread rate, smolder reaction temperature, and products of combustion (solid and gas). On both the first mission on STS-69 and the second mission on STS-77, a smolder front propagated the length of the forced-flow samples, with the spread rate between the corresponding upward and downward 1g smolder rates. Neither of the quiescent cases propagated combustion (the first case was due in part to a problem with the experiment electronics). These results show a dramatic difference from the normal gravity results, where smolder propagation is very rapid and complete for both of these conditions. The experiment was conceived by Prof. A. Carlos Fernandez-Pello at the University of California-Berkeley. The MSC hardware was designed and built at the NASA Lewis Research Center by a team of civil servants and contractors from NYMA, Inc., and Aerospace Design & Fabrication, Inc. (ADF). The hardware consists of two sealed aluminum combustion chambers (each being a half a cylinder). The chambers hold the MSC test section, data acquisition electronics, power distribution electronics, and instrumentation. The hardware is fitted into a 5-ft(sup 3) Get-Away-Special (GAS) canister that is mounted in the shuttle cargo bay. The test section consists of a quartz cylinder that contains the polyurethane foam sample and an igniter. This igniter, which is an electrically heated wire sandwiched between two porous ceramic disks, is mounted in contact with the end of the foam sample. An array of 12 thermocouples placed axially and radially along the foam sample provide temperature histories, which are used to determine the rate of smolder propagation, and the characteristics of the reaction.

Koudelka, John M.↗