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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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At least 1,315 records · Page 73
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NASA NTRS2020

Discovery of Abundant Tremolite in a Carbonaceous Chondrite Fragment from the Almahata Sitta Meteorite

Almahata Sitta (AhS) is classified as an anomalous, polymict ureilite and was observed prior to Earth impact as the F-type asteroid 2008 TC3 [e.g., 1-2]. As part of our characterization of this unusual meteorite [e.g., 3], we have been using microscopic infrared spectroscopy (µ-FTIR) to measure the mineralogy of fragments identified as carbonaceous chondrites (CC). In fragment 202 we have discovered unambiguous spectral evidence for a minimum of several vol% amphibole (specifically, tremolite), a mineral that is not known to occur in volumetrically significant abundances (defined here as >1%) in carbonaceous chondrites

Hamilton, V. E.↗
NASA NTRS2021

Hydrogen Abundance and Distribution on (101955) Bennu

Asteroids were likely a major source of volatiles and water to early Earth. Quantifying the hydration of asteroids is necessary to constrain models of the formation and evolution of the Solar System and the origin of Life on Earth. The OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer) mission showed that near-Earth asteroid (101955) Bennu contains widespread, abundant hydrated phyllosilicates, indicated by a ubiquitous absorption at ~ 2.7 μm. The objective of this work is to quantify the hydration—that is, the hydrogen content—of phyllosilicates on Bennu's surface and investigate how this hydration varies spatially. We analyse spectral parameters (normalized optical path length, NOPL; effective single-scattering albedo, ESPAT; and Gaussian modeling) computed from the hydrated phyllosilicate absorption band of spatially resolved visible–near-infrared spectra acquired by OVIRS (the OSIRIS-REx Visible and InfraRed Spectrometer). We also computed the same spectral parameters using laboratory-measured spectra of meteorites including CMs, CIs, and the ungrouped C2 Tagish Lake. We estimate the mean hydrogen content of water and hydroxyl groups in hydrated phyllosilicates on Bennu's surface to be 0.71 ± 0.16 wt%. This value is consistent with the hydration range of some aqueously altered meteorites (CMs, C2 Tagish Lake), but not the most aqueously altered group (CIs). The sample collection site of the OSIRIS-REx mission has slightly higher hydrogen content than average. Spatial variations in hydrogen content on Bennu's surface are linked to geomorphology, and may have been partially inherited from its parent body.

A. Praet↗
NASA NTRS2021

Improved Representation of the Global Dust Cycle Using Observational Constraints on Dust Properties and Abundance

Even though desert dust is the most abundant aerosol by mass in Earth’s atmosphere, atmospheric models 25 struggle to accurately represent its spatial and temporal distribution. These model errors are partially caused byfundamental difficulties in simulating dust emission in coarse-resolution models and in accurately representing dust microphysical properties. Here we mitigate these problems by developing a new methodology that yields an improved representation of the global dust cycle. We present an analytical framework that uses inverse modeling to integrate an ensemble of global model simulations with observational constraints on the dust size distribution, 30 extinction efficiency, and regional dust aerosol optical depth. We then compare the inverse model results against independent measurements of dust surface concentration and deposition flux and find that errors are reduced by approximately a factor of two relative to current model simulations of the Northern Hemisphere dust cycle. The inverse model results show smaller improvements in the less dusty Southern Hemisphere, most likely because both the model simulations and the observational constraints used in the inverse model are less accurate. On a global 35 basis, we find that the emission flux of dust with geometric diameter up to 20 μm (PM20) is approximately 5,000 Tg/year, which is greater than most models account for. This larger PM20 dust flux is needed to match observational constraints showing a large atmospheric loading of coarse dust. We obtain gridded data sets of dust emission, vertically integrated loading, dust aerosol optical depth, (surface) concentration, and wet and dry deposition fluxes that are resolved by season and particle size. As our results indicate that this data set is more accurate than current 40 model simulations and the MERRA-2 dust reanalysis product, it can be used to improve quantifications of dust impacts on the Earth system.

aerosols, dust↗
NASA NTRS2021

Improved representation of the global dust cycle using observational constraints on dust properties and abundance

Even though desert dust is the most abundant aerosol by mass in Earth's atmosphere, atmospheric models struggle to accurately represent its spatial and temporal distribution. These model errors are partially caused by fundamental difficulties in simulating dust emission in coarse-resolution models and in accurately representing dust microphysical properties. Here we mitigate these problems by developing a new methodology that yields an improved representation of the global dust cycle. We present an analytical framework that uses inverse modeling to integrate an ensemble of global model simulations with observational constraints on the dust size distribution, extinction efficiency, and regional dust aerosol optical depth. We then compare the inverse model results against independent measurements of dust surface concentration and deposition flux and find that errors are reduced by approximately a factor of 2 relative to current model simulations of the Northern Hemisphere dust cycle. The inverse model results show smaller improvements in the less dusty Southern Hemisphere, most likely because both the model simulations and the observational constraints used in the inverse model are less accurate. On a global basis, we find that the emission flux of dust with a geometric diameter up to 20 µm (PM20) is approximately 5000 Tg yr−1, which is greater than most models account for. This larger PM20 dust flux is needed to match observational constraints showing a large atmospheric loading of coarse dust. We obtain gridded datasets of dust emission, vertically integrated loading, dust aerosol optical depth, (surface) concentration, and wet and dry deposition fluxes that are resolved by season and particle size. As our results indicate that this dataset is more accurate than current model simulations and the MERRA-2 dust reanalysis product, it can be used to improve quantifications of dust impacts on the Earth system.

Dust cycle↗
NASA NTRS2023

The Projected Future Degradation in Air Quality is Caused by More Abundant Natural Aerosols in a Warmer World

Previous studies suggest that greenhouse gas-induced warming can lead to increased fine particulate matter concentrations and degraded air quality. However, significant uncertainties remain regarding the sign and magnitude of the response to warming and the underlying mechanisms. Here, we show that thirteen models from the Coupled Model Intercomparison Project Phase 6 all project an increase in global average concentrations of fine particulate matter in response to rising carbon dioxide concentrations, but the range of increase across models is wide. The two main contributors to this increase are increased abundance of dust and secondary organic aerosols via intensified West African monsoon and enhanced emissions of biogenic volatile organic compounds, respectively. Much of the inter-model spread is related to different treatment of biogenic volatile organic compounds. Our results highlight the importance of natural aerosols in degrading air quality under current warming, while also emphasizing that improved understanding of biogenic volatile organic compounds emissions due to climate change is essential for numerically assessing future air quality.

Climate and Earth system modelling↗
NASA NTRSDate not supplied

Timing, Abundance, and Spatial Extent of Initial Magmatism on the Moon Explained By Cumulate Mantle Overturn

We have recently quantified the timing, abundance, and spatial extent of lower mantle melting induced by cumulate overturn on the Moon through a series of 3D geodynamical models. Our dynamical modeling indicates that overturn of thin (~30-50 km) and weak ilmenite-bearing cumulates (IBC) triggers a rapid, short-lived, and widespread period of lower mantle melting which reproduces the key geochronological, volume, and spatial characteristics associated with the onset of secondary magmatism on the Moon (Figs. 1,2), and without energy contributions from KREEP (potassium, rare earth elements, phosphorus, radiogenic U, Th). Within the guiding paradigms of global differentiation via magma ocean crystallization and subsequent cumulate mantle overturn, our model provides explanation for near contemporaneous primary and secondary crust production constrained by geochronology of returned lunar samples and meteorites. In this abstract, we discuss our results in context with several intricacies of lunar chronology including models of a long-lived magma ocean, the hypothesis that mantle overturn was induced by the giant South Pole-Aitken basin forming impact, and ancient lunar zircon.

T. C. Prissel↗
NASA NTRS2024

Carbon and Nitrogen Abundance, Distribution, and Isotopic Composition in Samples of Asteroid (101955) Bennu

Material from the B-type carbonaceous asteroid (101955) Bennu was returned on September 24, 2023, by NASA’s OSIRIS-REx mission. The mission brought back the largest sample of pristine primordial asteroidal material, largely free from the challenges of terrestrial contamination that are common in meteorite studies. The Bennu sample thus provides a unique source of material to investigate the abundance and isotopic signatures of C and N. The specific hypotheses tested by these analyses are whether Bennu contains macromolecular material and/or presolar grains similar to the populations found in CI and CM chondrites and recently returned samples from Ryugu.

M. M. Grady↗
NASA NTRSDate not supplied

Sinus Viscositatis: Implications of Young, KREEPy Mare Eruptions for Lunar Volatile Abundances and Origins

Volatiles such as H 2 O and OH have been conclusively shown to exist across the Moon following over a decade of detailed sample analysis and remote sensing. Several mechanisms deliver volatiles to the lunar surface, including exogenous sources such as asteroid or comet bombardment (i.e., H 2 O, CO 2 , CH 4 , NH 3 , S), solar wind (i.e., H, He, Ne, Ar, Na, C, O), and galactic cosmic rays (i.e., noble gases like Xe), or endogenous sources such as outgassing from igneous lithologies (i.e., H 2 O, OH, CO 2 , S, Ar, Cl, F). Processes such as impact gardening and temperature-driven adsorption/desorption have likely supported further transport of species across the lunar surface, thus a mixture of sources is thought to be preserved. Nonetheless, volatile origins, abundances, and cycling on the Moon are not well understood and require further investigation.

A. J. Gawronska↗
NASA NTRSDate not supplied

Atmospheric Structure Investigation Instrument: in-Situ Measurement of Vertical Profiles of Temperature, Pressure, Wind, Aerosol Density, Hydrogen Ortho/Para Fraction and Helium Abundance on Saturn or Uranus.

The Atmospheric Structure Investigation (ASI) is designed as a threshold sensor suite for descent probes into any planetary atmosphere, principally for the Giant planets (e.g., Saturn for New Frontiers, or Uranus for an upcoming Flagship identified in the decadal survey), but also could be relevant for Venus, Titan or even specific applications on Earth. Its aim is to supply the key measurements establishing the atmospheric structure upon which all the other probe measurements would be placed in context. To that end, it measures vertical profiles of probe acceleration and rotation[1,2], pressure, temperature, vertical winds, aerosol number density and size and scattering properties, as well as Hydrogen ortho/para fraction and Helium abundance.

V Jha↗
NASA NTRS2025

Abundant Ammonia and Nitrogen-Rich Soluble Organic Matter in Samples From Asteroid (101955) Bennu

Organic matter in meteorites reveals clues about early Solar System chemistry and the origin of molecules important to life, but terrestrial exposure complicates interpretation. Samples returned from the B-type asteroid Bennu by the Origins, Spectral Interpretation, Resource Identifcation, and Security–Regolith Explorer mission enabled us to study pristine carbonaceous astromaterial without uncontrolled exposure to Earth’s biosphere. Here we show that Bennu samples are volatile rich, with more carbon, nitrogen and ammonia than samples from asteroid Ryugu and most meteorites. Nitrogen-15 isotopic enrichments indicate that ammonia and other N-containing soluble molecules formed in a cold molecular cloud or the outer protoplanetary disk. We detected amino acids (including 14 of the 20 used in terrestrial biology), amines, formaldehyde, carboxylic acids, polycyclic aromatic hydrocarbons and N-heterocycles (including all fve nucleobases found in DNA and RNA), along with ~10,000 N-bearing chemical species. All chiral non-protein amino acids were racemic or nearly so, implying that terrestrial life’s left-handed chirality may not be due to bias in prebiotic molecules delivered by impacts. The relative abundances of amino acids and other soluble organics suggest formation and alteration by low-temperature reactions, possibly in NH3-rich fuids. Bennu’s parent asteroid developed in or accreted ices from a reservoir in the outer Solar System where ammonia ice was stable.

Daniel P Glavin↗
DOE OSTI2025

Controlling Oxidation of Nb in Oxygen Abundant Environments.

Superconducting Radio Frequency (SRF) cavities, the core of modern particle accelerators, rely on high-purity niobium (Nb) to achieve high quality factors and accelerating gradients. However, native oxidation in ambient conditions introduces a complex oxide layer with increased surface defects and contamination, particularly from carbon. This research explores a controlled oxidation processes in an oxygen-abundant environment to try to control this complex oxide stack, with the goal of improving surface purity and uniformity. Using standard surface preparation techniques—including electropolishing, vacuum baking, and sonication—followed by a custom oxidation protocol, we compared structural and chemical changes through Confocal Microscopy, Scanning Electron Microscopy (SEM), and X-Ray Photoelectron Spectroscopy (XPS). Results show that iterative oxidation cycles can significantly reduce carbon-related defects, even without baking. Aditionally, baked samples with a specific oxidation technique demonstrated a measurable 25\% decrease in carbide formation.

Romero, Juan [Fermilab]↗
DOE OSTI2022

On the inconsistency of [C/Fe] abundances and the fractions of carbon-enhanced metal-poor stars among various stellar surveys

Carbon-enhanced metal-poor (CEMP) stars are a unique resource for Galactic archaeology because they probe the properties of the First Stars, early chemical evolution, and binary interactions at very low metallicity. Comparing the fractions and properties of CEMP stars in different Galactic environments can provide us with unique insights into the formation and evolution of the Milky Way halo and its building blocks. In this work, we investigate whether directly comparing fractions of CEMP stars from different literature samples of very metal-poor [Fe/H] < -2.0 stars is valid. We compiled published CEMP fractions and samples of Galactic halo stars from the past 25 years, and find that they are not all consistent with each other. Focusing on giant stars, we find significant differences between various surveys when comparing their trends of [Fe/H] versus [C/Fe] and their distributions of CEMP stars. To test the role of the analysis pipelines for low-resolution spectroscopic samples, we re-analysed giant stars from various surveys with the sspp and ferre pipelines. We found systematic differences in [C/Fe] of ~0.1-0.4 dex, partly independent of degeneracies with the stellar atmospheric parameters. These systematics are likely due to the different pipeline approaches, different assumptions in the employed synthetic grids, and/or the comparison of different evolutionary phases. We conclude that current biases in (the analysis of) very metal-poor samples limit the conclusions one can draw from comparing different surveys. We provide some recommendations and suggestions that will hopefully aid the community to unlock the full potential of CEMP stars for Galactic archaeology.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

The KLEVER survey: nitrogen abundances at z ~ 2 and probing the existence of a fundamental nitrogen relation

Here we present a comparison of the nitrogen-to-oxygen ratio (N/O) in 37 high-redshift galaxies at z ~ 2 taken from the KMOS Lensed Emission Lines and VElocity Review (KLEVER) Survey with a comparison sample of local galaxies, taken from the Sloan Digital Sky Survey (SDSS). The KLEVER sample shows only a mild enrichment in N/O of +0.1 dex when compared to local galaxies at a given gas-phase metallicity (O/H), but shows a depletion in N/O of –0.35 dex when compared at a fixed stellar mass (M * ). We find a strong anticorrelation in local galaxies between N/O and SFR in the M * –N/O plane, similar to the anticorrelation between O/H and SFR found in the mass–metallicity relation (MZR). We use this anticorrelation to construct a fundamental nitrogen relation (FNR), analogous to the fundamental metallicity relation (FMR). We find that KLEVER galaxies are consistent with both the FMR and the FNR. This suggests that the depletion of N/O in high-z galaxies when considered at a fixed M * is driven by the redshift evolution of the mass–metallicity relation in combination with a near redshift-invariant N/O–O/H relation. Furthermore, the existence of an fundamental nitrogen relation suggests that the mechanisms governing the fundamental metallicity relation must be probed by not only O/H, but also N/O, suggesting pure-pristine gas inflows are not the primary driver of the FMR, and other properties such as variations in galaxy age and star formation efficiency must be important.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1996

Galactic Abundance Gradients fro IR Fine Strucuture LInes in Compact H II regions

We present observations of the [S III]19(micro)m, [O III]52 and 88(micro)m, and [N III]57(micro)m lines toward 18 compact and ultracompact (UC) H II regions. These data were combined with data from the literature and high-resolution radio continuum maps to construct detailed statistical equilibrium and ionization equilibrium models of 34 compact H II regions located at galactocentric distances (Dg)0-12kpc. Our models simultaneously fit the observed IR fine-structure lines and high-resolution radio continuum maps.

galactic elements chemical evolution galaxy format↗
NASA NTRS1994

The Abundances of Methane and Ortho/Para Hydrogen in Uranus and Neptune: Implications of New Laboratory 4-0 H(sub 2) Quadrapole Line Parameters

The tropospheric methane molar fraction (f(sub ch4,t)) and the ortho/para hydrogen ratio are derived for Uranus and Neptune based on new determinations of spectroscopic parameters for key hydrogen features as reported by Ferguson et al. (1993, J. Mol. Spec 160, 315-325). For each planet, the relatively weak laboratory linestrengths (approximately 30% and 15% less than the theoretical 4-0 S(0) and S(1) linestrengths, respectively) results, when compared to analyses adopting theoretical values, in a ~30% decrease in the tropospheric methane ratio and a comparable increase in the pressure level of the optically-thick cloudtop marking the bottom of the visible atmosphere (P(sub cld)).

Uranus atmosphere; Neptune atmosphere; abundances ↗