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NASA NTRSDate not supplied

Extinction of the Stagnation Point Diffusion Flame: Effect of Conductive Heat Loss into Solid Interior

The planned microgravity experiment Growth and Extinction Limit (GEL) is designed to study the material flammability and extinction of thermally thick solid with an emphasis to quantify the effect of conductive heat loss into the solid interior by measuring the in-depth temperature profile. To obtain a more detailed understanding of the extinction phenomena, a previously developed one-dimensional axisymmetric stagnation-point diffusion flame model is expanded to account for the excessive heat loss into the solid beyond the steady burning state. This is important because for thick solids, this is important because the burning period can have a long and slow solid transient with a quasi-steady gas -phase. A non-dimensional excessive conductive heat loss parameter Ψ is defined in the paper and extensive numerical computations have been performed to determine the extinction boundary and the characteristics of near-limit flames. The classical U-shaped flammability boundary in the oxygen vs. stretch rate plot now becomes a series of U-shaped boundaries as a function of Ψ. For a given oxygen ambient, extinction boundary is a function of Ψ. The boundary consists of a blowoff branch and a radiative quenching branch. This is similar to the steady burning flammability boundary (Ψ =0) in the oxygen vs stretch rate plot. Extensive computed data including flame and pyrolysis temperatures, burning rate, flame standoff distance, and reaction rate are presented along the extinction boundaries. In particular, we note that the non-dimensional gas reaction rate is the ratio of diffusion reaction time to the reaction diffusion time, so it has the classical Damhkoler number character. By examining the maximum non-dimensional reaction rates, we observe that along the extinction boundaries, they are approximate constant across the entire range of stretch rates (from quenching to blow-off). These critical values are of the order unity but may vary in different oxygen ambient. The implication will be discussed in the presentation together with the near-limit flame structures.

Chengyao Li↗
NASA NTRS2022

The Lithophile Element Budget of Earth’s Core

The relative composition of Earth’s core and mantle were set during core formation. By determining how elements partition between metal and silicate at high pressures and temperatures, measurements of the mantle composition and geophysical observations of the core can be used to understand the mechanisms by which Earth formed. Here we present the results of metal–silicate partitioning experiments for a range of nominally lithophile elements (Al, Ca, K, Mg, O, S, Si, Th, U) and S to 85 GPa and up to 5400 K. With our results and a compilation of literature data, we developed a parameterization for partitioning that accounts for compositional dependencies in both the metal and silicate phases. Using this parameterization in a range of planetary growth models, we find that, in general, lithophile element partitioning into the metallic phase is enhanced at high temperatures. The relative abundances of FeO, SiO2 and MgO in the mantle vary significantly between planetary growth models, and the mantle abundances of these elements can be used to provide important constraints on Earth’s accretion. To match Earth’s core mass and mantle composition, Earth’s building blocks must have been enriched in Fe and depleted in Si compared with CI chondrites. Finally, too little Mg, Si and O are partitioned into the core for precipitation of oxides to be a major source of energy for the geodynamo. In contrast, several ppb of U can be partitioned into the core at high temperatures, and this energy source must be accounted for in thermal evolution models.

dynamo↗
NASA NTRS2021

Exploring Sentinel-1 and Sentinel-2 diversity for Flood inundation mapping using deep learning

Identification of flood water extent from satellite images has historically relied on either synthetic aperture radar (SAR) or multi-spectral (MS) imagery. MS sensors are limited to cloud free conditions, whereas SAR imagery is plagued by noise-like speckle. Prior studies that use combinations of MS and SAR data to overcome individual limitations of these sensors have not fully examined sensitivity of flood mapping performance to different combinations of SAR and MS derived spectral indices or band transformations in color space. This study explores the use of diverse bands of Sentinel 2 (S2) through well-established water indices and Sentinel 1 (S1) derived SAR imagery along with their combinations to assess their capability for generating accurate flood inundation maps. The robustness in performance of S-1 and S-2 band combinations was evaluated using 446 hand labeled flood inundation images spanning across 11 flood events from Sen1Floods11 dataset which are highly diverse in terms of land cover as well as location. A modified K-fold cross validation approach is used to evaluate the performance of 32 combinations of S1 and S2 bands using a fully connected deep convolutional neural network known as U-Net. Our results indicated that usage of elevation information has improved the capability of S1 imagery to produce more accurate flood inundation maps. Compared to a median F1 score of 0.62 when using only S1 bands, the combined use of S1 and elevation information led to an improved median F1 score of 0.73. Water extraction indices based on S2 bands have a statistically significant superior performance in comparison to S1. Among all the band combinations, HSV (Hue, Saturation, Value) transformation of S2 bands provides a median F1 score of 0.9, outperforming the commonly used water spectral indices owing to HSV’s transformation’s superior contrast distinguishing abilities. Additionally, U-Net algorithm was able to learn the relationship between raw S2 based water extraction indices and their corresponding raw S2 bands, but not of HSV owing to relatively complex computation involved in the latter. Results of the paper establishes important benchmarks for the extension of S1 and S2 data-based flood inundation mapping efforts over large spatial extents.

Goutam Konapala↗
NASA NTRSDate not supplied

Space-based UV Spectropolarimetry for Chromospheric Magnetic Field Measurements

High-resolution observations with space-and ground-based telescopes, along with advanced numerical modeling, have highlighted the intricate coupling between the chromosphere, transition region, and corona, and the critical role the chromosphere plays in the mass and energy balance of the outer solar atmosphere. Despite these recent advances, a major impediment to better understanding the solar atmosphere is our lack of empirical knowledge regarding the direction and strength of the magnetic field in the upper chromosphere (Decadal Survey, 2012). Such measurements are crucial to address several major unresolved issues in solar physics: for example, to constrain the energy flux carried by the Alfvén waves propagating through the chromosphere, and to determine the height at which the plasma β = 1 transition occurs, which has important consequences for the braiding of magnetic fields, for propagation and mode conversion of waves and for non-linear force-free extrapolation methods that are key to determining what drives instabilities such as flares or coronal mass ejections. Probing the magnetic nature of the Sun’s atmosphere requires measurement of the Stokes I, Q, U and V profiles of relevant spectral lines (of which Q, U and V encode the magnetic field information). Many of the magnetically sensitive lines formed in the chromosphere and transition region are in the ultraviolet spectrum, necessitating observations above the absorbing terrestrial atmosphere. The Chromospheric Layer Spectro-Polarimeter (“CLASP2”) sounding rocket was flown successfully in April 2019, as a follow-on to the successful flight in September 2015 of the Chromospheric Lyman-Alpha Spectro-Polarimeter (“CLASP1”). In October of 2021, we re-flew the CLASP2 experiment with a modified observing program to further demonstrate the maturity of the UV spectropolarimetry techniques, and readiness for development into a satellite observatory. During the reflight, called “CLASP2.1”, the spectrograph slit was scanned across an active region plage to acquire a two-dimensional map of Stokes V/I, to demonstrate the ability of UV spectropolarimetry to yield chromospheric magnetic fields over a large area.

David E McKenzie↗
NASA NTRS2017

Constraints on Mechanisms of Chondrule Formation from Chondrule Precursors and Chronology of Transient Heating Events in the Protoplanetary Disk

The mineralogy, petrography, and oxygen-isotope compositions of porphyritic chondrules—dominant chondrule type in most chondrite groups—suggest formation by incomplete melting of isotopically diverse precursors during localized transient heating events in dust-rich regions of the protoplanetary disk characterized by 16O-poor compositions (D17Odust+gas~ –7‰ to +4‰) relative to the inferred Sun’s value (D17O ~ –28 ± 2‰). The chondrule precursors included Ca,Al-rich inclusions (CAIs), amoeboid olivine aggregates (AOAs), chondrules of earlier generations, fine-grained matrix-like material, and possibly fragments of pre-existing planetesimals. Like porphyritic chondrules, igneous CAIs formed by melting of isotopically diverse precursors during transient heating events, but in an isotopically distinct, solar-like reservoir of the protoplanetary disk (D17O dust + gas ~ –24‰), probably near the proto Sun. Based on a narrow range of the initial 26Al/27Alratios inferred from the internal Al-Mg isochrons in igneous CAIs, their melting started at the very beginning of Solar System formation (t0), defined by the CV CAIs with U-corrected Pb-Pb age of 4567.3 ± 0.16 Ma and the canonical 26Al/27Al ratio of (5.25 ± 0.02) ¥ 10–5, and lasted at least 0.3 Ma. The U-corrected Pb-Pb absolute and 26Al-26Mg relative ages of porphyritic chondrules from type 3 ordinary, CO, CV, and CR carbonaceous chondrites (assuming uniform distribution of 26Al in the disk at the canonical level) suggest chondrule formation started at t0 and lasted for about 4 Ma. These observations may preclude formation of the majority of porphyritic chondrules by splashing of differentiated planetesimals and by collisions between planetesimals; instead, they are consistent with melting of dust balls by bow shocks or magnetized turbulence in the disk. Some porphyritic chondrules in equilibrated (petrologic type 4–6) ordinary chondrites contain relict fragments of coarse-grained chromite, ilmenite, phosphates, and albitic plagioclase. The similar mineral assemblage is commonly observed in type 4–6 ordinary chondrites, but is absent in type 3 chondrites, suggesting these chondrules formed by incomplete melting of thermally metamorphosed ordinary chondrite material, possibly by impacts. The CB metal-rich carbonaceous chondrites contain exclusively magnesian non-porphyritic chondrules crystallized from complete melts. These chondrules formed in a gas-melt plume generated by a hypervelocity (≥20 km/s) collision between planetesimals ~4.8 Ma after t0 in a transition or a debris disk. One of the colliding bodies was probably differentiated. The CH metal-rich carbonaceous chondrites contain chondrules formed by different mechanisms. The magnesian non-porphyritic chondrules formed in the CB impact plume ~4.8 Ma after t0. The chemically diverse (magnesian, ferroan, and Al-rich) porphyritic chondrules formed by incomplete melting of isotopically diverse precursors in the protoplanetary disk, most likely prior the CB impact plume event. We conclude that there are multiple mechanisms of chondrule formation that operated over the entire life-time of the disk.

Chondrules↗
NASA NTRS2021

Stokes resolved differential temperature: an important metric of polarimetric precision in the long-wave infrared

In remote sensing, radiometric measurements taken in the mid-wave infrared and beyond (λ >3μm) are commonly reported in units of Kelvin by utilizing Planck’s radiation law to relate measured radiance and target brightness temperature (Tb). Thus, it is desirable to match this formalism in thermal polarimetry and report the unnormalized Stokes parameters in units of K instead of radiance (Wm−2sr−1). This approach also al-lows common performance metrics in long-wave infrared (LWIR) imaging such as Noise Equivalent DifferentialTemperature (NEDT) to be modified and extended to metrics of polarimetric accuracy and precision. However, since the relationship between measured radiance and Tb are non-linear, the conversion of I, Q, and U in units of radiance to Tb,Tb,Q, and Tb,U in K is ambiguous. As a solution a metric of performance for thermal linear Stokes polarimetry, the Stokes resolved differential temperature (SRDT), is introduced.

polarimetry↗
NASA NTRS2022

The Impacts of Freshwater Input and Surface Wind Velocity on the Strength and Extent of a Large High Latitude River Plume

Arctic Ocean physical and biogeochemical properties are strongly influenced by freshwater input from land and through the Bering Strait, where the mean currents transport water northward from the Bering Sea. The Yukon River is one of the largest rivers in North America and the Arctic, contributing large quantities of freshwater and terrigenous material to the coastal ocean in the northern Bering Sea. However, a detailed analysis of the coastal hydrodynamics at the outflow of the river has not been conducted in this remote but regionally important river. A three-dimensional hydrodynamic model was built to represent the lower Yukon River and coastal ocean for the ice-free months in 7 years. On average, a large anticyclonic eddy persisted at the main outflow of the Yukon that recirculates water back toward the coast where the currents converge to form a mean northward transport along the delta. Interannual spatial variance in salinity was relatively small, while there was substantial variance in u and v current velocity. u velocity spatial variance was correlated to the volume of freshwater discharge across years, while v velocity spatial variance was correlated to the N–S wind velocity. During strong wind events, plume structure was substantially altered: southerly winds deepened the plume and enhanced northward transport, while northerly winds shoaled and strengthened the pycnocline, and reversed the flow toward the south. The variability in plume dispersion on short time scales due to wind forcing has implications for where terrigenous material is processed in and settles out of the water column.

river plume↗
NASA NTRS2023

Temperature Effect on Silicate Melt-Sulfide-Metal Trace Element Partitioning in the Presence of Sulfur Under Reduced Conditions

The reduced nature of Mercury, enstatite chondrites, and the aubrite parent bodies (APB) have raised many questions regarding the geochemical behavior of typically lithophile, heat-producing, and rare-earth elements (REE) in magmas at low oxygen fugacity (fO2). Due to decreasing O availability at these low fO2, and an abundance of S(sup 2(-)), sulfur (S) acts as an important anion that changes the partitioning behavior of many elements and modifies the physical properties of silicate melts. Preliminary observations suggest that major and minor elements exhibit different geochemical affinities in highly reduced, S-rich systems compared to terrestrial rocks. The speciation and bonding environment of S, dictated by P/T/fO2 conditions, may strongly influence the degree to which S affects partitioning behavior. Here we investigate the partitioning behavior of major, minor, and trace elements between silicate melt, sulfide melt, and metal as well as the coordination chemistry of S in highly reduced silicate melts. Our work is focused on investigating solely the entropy-dependent temperature effect on partitioning of elements for which we currently have MESSENGER data (K, Na, Th, U, Si, Mg, Fe, Ti, Ca, Al, Cr, Mn, S, Cl) as well as a host of geochemically relevant trace elements such as REEs (P, Co, Ni, Mo, Ce, Nd, Sm, Eu, Gd, Dy, Yb). Previous studies in which temperature, pressure, and fO2 were co-varied found that as fO2 decreases, heat-producing elements U and Th become more chalcophile, while K becomes less chalcophile. Concurrently, nominally lithophile elements Mg and Ca become more chalcophile and were observed as minor elements in exsolved sulfides and bonded with S species in silicate melt. These studies, however, could not disentangle entropic effects from changes in the fO2. New temperature-dependent partitioning data from our work will be used to determine which elements are most likely to retain their lithophile character and hence be incorporated into silicates, and which elements are likely contained within the sulfide (chalcophile) and metal core (siderophile), setting the stage for the thermal and magmatic evolution of reduced planetary bodies.

B A Anzures↗
NASA NTRS2016

Is the Pale Blue Dot Unique? Optimized Photometric Bands for Identifying Earth-Like Exoplanets

The next generation of ground- and space-based telescopes will image habitable planets around nearby stars. A growing literature describes how to characterize such planets with spectroscopy, but less consideration has been given to the usefulness of planet colors. Here, we investigate whether potentially Earth-like exoplanets could be identified using UV-visible-to-NIR wavelength broadband photometry (350–1000 nm). Specifically, we calculate optimal photometric bins for identifying an exo-Earth and distinguishing it from uninhabitable planets including both Solar System objects and model exoplanets. The color of some hypothetical exoplanets—particularly icy terrestrial worlds with thick atmospheres—is similar to Earth's because of Rayleigh scattering in the blue region of the spectrum. Nevertheless, subtle features in Earth's reflectance spectrum appear to be unique. In particular, Earth's reflectance spectrum has a “U-shape” unlike all our hypothetical, uninhabitable planets. This shape is partly biogenic because O2-rich, oxidizing air is transparent to sunlight, allowing prominent Rayleigh scattering, while ozone absorbs visible light, creating the bottom of the “U.” Whether such uniqueness has practical utility depends on observational noise. If observations are photon limited or dominated by astrophysical sources (zodiacal light or imperfect starlight suppression), then the use of broadband visible wavelength photometry to identify Earth twins has little practical advantage over obtaining detailed spectra. However, if observations are dominated by dark current, then optimized photometry could greatly assist preliminary characterization. We also calculate the optimal photometric bins for identifying extrasolar Archean Earths, and find that the Archean Earth is more difficult to unambiguously identify than a modern Earth twin.

Astrobiology↗
NASA NTRS2022

Near-Earth Object Surveyor Overview

The Near-Earth Object (NEO) Surveyor is designed to detect, categorize and characterize Near-Earth Objects (NEOs) using infrared imaging. The project was approved to enter the preliminary design phase (Phase B) in FY21 after an extended Concept Development Phase (Phase A). The NEO Surveyor project responds to US Public Law 109-155[1], National Research Council’s report “Defending Planet Earth: Near-Earth Object Surveys & Hazard Mitigation Strategies (2010)”[2], the U. S. National Near-Earth Object Preparedness Strategy and Action Plan (June 2018)[3], and the objectives of NASA’s Planetary Defense Coordination Office (PDCO). The goals of the NEO Surveyor project are to: (1) identify impact hazards to the Earth posed by NEOs (defined as asteroids and comets that come within 1.3 AU of the Sun) by performing a comprehensive survey of the NEO population; (2) obtain detailed physical characterization data for individual objects that are likely to pose an impact hazard; (3) characterize the entire population of potentially hazardous NEOs to inform potential mitigation strategies. The mission will make significant progress toward the George E. Brown, Jr. NEO Survey Program objective defined by the U. S. Congress of detecting, tracking, cataloging, and characterizing at least 90% of NEOs equal to or larger than 140 m in diameter. The project is a collaboration between NASA-JPL, the University of Arizona (UA) and industry, with Ball Aerospace notably providing the spacecraft and key instrument elements. This paper will describe the overall NEO Surveyor Project objectives, initial spacecraft and instrument design and development plans and mission concept.

Veto, Michael↗
NASA NTRSDate not supplied

3-D Mapping of the Magnetic Field in the Active Region by the CLASP2.1 Rocket Experiment

Comprehensive magnetic field measurements of the solar atmosphere are crucial for understanding energy transport from the photosphere to the corona and its dissipation. However, observations of the magnetic field in the chromosphere and the upper atmospheric layers above the chromosphere, where the gas pressure dominance changes from (β>1) to magnetic pressure dominance (β<1), are overwhelmingly lacking. Therefore, we have focused on the polarization of ultraviolet radiation emitted from the upper chromosphere and transition layer and have conducted the Japan-U.S.-EU observation rocket experiment CLASP in order to demonstrate its usefulness. In CLASP2.1 conducted on October 8, 2021, scan observations were made at 16 locations in the active region, and Stokes (intensity $I$, linearly polarized $Q$, $U$, circularly polarized $V$) spectra in the 280~nm wavelength range were obtained. Looking at the observed region with AIA 171~{¥AA} on board the SDO satellite, we see that it consists of a region where a structure corresponding to the foot of a high-temperature loop called moss (moss) is seen, and a region where a low-temperature loop spreading from a sunspot is seen. We focused on the ionized magnesium $h$ & $k$ lines (emitted from the middle and uppermost of the chromosphere) and the manganese lines (emitted from the low part of the chromosphere), which show particularly prominent circular polarization, and derived the line-of-sight magnetic fields in the low, middle and uppermost parts of the chromosphere by applying weak field approximation to them. Furthermore, by combining the results with observations by the Solar Optical Telescope onboard the solar observing satellite HINODE, we obtained three-dimensional information on the magnetic field in the active region from the photosphere to the uppermost part of the chromosphere. In general, the magnetic field in the active region becomes weaker and smoother as one goes up in the sky, as reported by the CLASP2 observation (Ishikawa et al. 2021). However, in some regions, polarity reversal was observed only in the uppermost part of the chromosphere, and comparison with high spatial resolution transition layer and coronal images recorded by SDO/AIA revealed the connection between the magnetic field structure in the chromosphere and coronal loops.

R. Ishikawa↗
NASA NTRS2024

Evidence for a ~1 Ga Hypervelocity Impact Event Found in Northwest Greenland

There are likely many undiscovered impact structures on Earth, but several challenges prevent their detection, including possible concealment beneath large ice sheets. In recent years, geophysical, geochemical, and microphysical evidence has mounted for a ca. 58 Ma impact structure under the Hiawatha Glacier, northwest Greenland. Here, we report evidence for a second, much older hypervelocity impact event in this region, recorded in an impact melt rock sample collected from a glaciofluvial deposit in Inglefield Land. Secondary ion mass spectrometry U-Pb analyses of shock metamorphosed zircon grains yielded a previously unrecorded, Proterozoic best estimate impact age of 1039 ± 16 Ma (mean square of weighted deviates = 2.9). Based on Archean−Proterozoic target rock U-Pb ages obtained from unshocked zircon grains and the location of the melt rock sample along the ice margin, we suggest this sample was derived from a hypervelocity impact structure farther inland, concealed by the Greenland Ice Sheet. This study demonstrates the ability to uncover new impact events in some of the most inaccessible areas on Earth and the possibility of sampling multiple impact structures from one location when examining ex situ material. Our results have implications for current and future Martian and lunar returned samples that demonstrably bear complex impact histories.

William R. Hyde↗
NASA NTRSDate not supplied

Objectively Identifying Transverse Cirrus Bands in Tropical Cyclones using a Convolutional Neural Network

Transverse cirrus bands (TCBs) are bands of upper-level clouds regularly seen in mesoscale and synoptic-scale weather systems. In tropical cyclones, their appearance has been subjectively linked to intensification and the diurnal cycle. However, these hypothesized relationships have not been rigorously tested due to the subjective nature of TCBs in satellite images. A machine learning technique that successfully identifies TCBs objectively in imagery from the GOES-16 Advanced Baseline Imager (ABI) has been developed to solve this problem. The technique uses a U-Net convolutional neural network (CNN) that assigns a probability to each pixel in an image based on the likelihood of the pixel being associated with a TCB. Using the U-Net CNN, a database of TCBs from 2019 to 2022 was developed for the Atlantic tropical cyclone basin by defining an appropriate probability threshold that defines the difference between TCB and non-TCB pixels. This threshold is where the Jaccard score, calculated using manually identified TCBs and model identified TCBs, is maximized. Statistics for TCB occurrence will also be presented, including the relationships between TCBs and storm relative motion, shear relative direction, cardinal direction, tropical cyclone intensity, tropical cyclone intensification rates, and time of day.

John Mark Mayhall↗
NASA NTRS2026

A Modular Conjugate Heat Transfer Optimization Framework for Thermal Management of Electric Aircraft

Conjugate heat transfer (CHT) analysis and optimization is a powerful method for improving thermal management, as it simultaneously resolves the temperature distribution in both fluid and solid domains. This paper presents a modular, discrete adjoint-based CHT optimization capability integrated within the OpenMDAO/MPhys framework. A unique feature of the proposed framework is its flexibility to extend to multidisciplinary optimization, including aero-structural-thermal applications. The fluid domain is modeled using a finite-volume Computational Fluid Dynamics (CFD) solver, and the solid domain with a conduction heat transfer solver. A mixed Neumann-Dirichlet boundary condition is developed to enable full submersion of the solid geometry within the fluid domain, while ensuring consistent temperature and heat flux coupling at the CHT interface. Gradient-based optimization is performed; the gradients are efficiently computed using the discrete adjoint solvers implemented in DAFoam. To demonstrate the method, this paper considers two cases related to electric aircraft thermal management: a U-bend heat exchanger and an actively cooled battery pack. The U-bend case aims to minimize pressure loss while maximizing heat flux by changing the pipe geometry. The optimized design reduces pressure loss by 52.7% and increases total heat flux by 2.3%. In the battery pack case, a 3-by-3 cell configuration is cooled by ambient airflow, with constant heat generation prescribed in the cells. The battery casing shape serves as the design variable, and the objective function is a weighted sum of pressure loss and pack weight, subject to a maximum temperature constraint. The optimized design achieves a 44.6% reduction in pressure loss and a 1.5% reduction in weight, while satisfying the thermal constraint. To ensure the reliability of the optimized designs, this study validates coarse-mesh, steady-state predictions against fine-mesh unsteady simulations, demonstrating consistency within acceptable errors. This work demonstrates the potential of the developed framework to enable rapid, high-fidelity design of thermal management systems for electric aircraft.

heat transfer↗
NASA NTRSDate not supplied

First N 2 Profile for Venus’ Deep Lower Atmosphere

We present the first N 2 profile for Venus’ deep lower atmosphere (<15 km) and a constrained isotopic composition for cloud N 2 [1]. This work directly addresses unresolved questions for Venus using legacy observations. Prior to this work, there were no reported measurements for N 2 abundances at <15 km and the isotopic composition remained unconstrained [2]. The N 2 parameters are critical to understanding the evolution and thermal properties of the atmosphere [3-7]. Our N 2 results were obtained by re-analysis of data acquired in 1978 by the Pioneer Venus Large Probe Neutral Mass Spectrometer (LNMS) [8]. The archived mass spectra from 64.2 to 0.2 km were treated using the analytical procedures specifically developed for the LNMS [9-11]. Judicious peak fitting permitted disambiguation of (A) N 2 + and CO + at 28 u and (B) 14 N 15 N+, 13 CO + , and C 2 H 5 + at 29 u. Quality controls included comparing the (A) LNMS CO + /CO 2 + ratios to the NIST database and literature and (B) fitted counts for CO + to the expected counts of CO + calculated from C 18 O + and 13 CO + using the LNMS 16 O/ 18 O and 12 C/ 13 C ratios (obtained from CO 2 ). Our results show that N 2 is uniformly mixed across the deep lower atmosphere between ~0.2 and 15 km (2.49 ± 0.10 v%). In contrast, N 2 is non-uniformly mixed across the sub-cloud atmosphere and clouds (~15–59 km), where N 2 abundances increase by ~ 2-fold between ~15 km (2.45 ± 0.32 v%) and ~59-51 km (5.21 ± 0.18 v%). Using the cloud data, we also obtained a constrained 15 N/ 14 N ratio (2.93×10 -3 ± 0.13×10 -3 ) and δ 15 N value (-204 ± 35‰). Thus, the LNMS results [1] suggest that (A) the atmosphere is unstable at <15 km, (B) N 2 is not well-mixed >15 km, and (C) the cloud δ 15 N falls between Earth and the solar wind [12, 13]. Comparisons of the N 2 abundances and isotopic compositions for nitrogen, carbon, and oxygen to other Venus measurements will be discussed.

deep lower atmosphere↗
NASA NTRS2026

Thermodynamic Properties of Uranium-Zirconium Carbide Solid Solutions with Oxygen

Uranium-zirconium carbide solid solutions are potential candidates for fuel in space nuclear reactors. To support development of advanced robust fuels for space applications, (U y Zr 1-y )C x O z solid solutions were synthesized via carbothermic reduction with uranium, carbon, and oxygen contents raging from y=0.05 – 0.3, x=0.95 – 0.98, and z = 0.02 – 0.07. These solid solutions were subsequently characterized by X-ray diffraction and elemental combustion analysis. High-temperature oxidative drop solution calorimetry in molten sodium molybdate solvent at 1073 K was employed to determine the formation, oxidation, and mixing enthalpies of (U y Zr 1-y )C x O z solid solutions, and thereby for evaluating their thermodynamic stability. The solid solutions are enthalpically less stable than the UC and ZrC end members. They also become less stable and more reactive towards oxidation with increasing uranium content. Incorporation of oxygen into solid solutions increases their solid solution-stability and improves their oxidation resistance.

Calorimetry↗
NASA NTRS1973

Trace element abundances and petrology of separates from Apollo 15 soils

Nine petrographically distinct separates from Apollo 15 coarse soils were characterized by electron microprobe and analyzed by neutron activation analysis for Ag, Au, Bi, Br, Cd, Cs, Ge, In, Ir, Rb, Re, Sb, Se, Te, Tl, U, and Zn. Like some alkali-poor anorthosites from Apollo 16, 15102 anorthosite is low in meteoritic siderophiles but enriched in Tl, perhaps by volcanic processes. Norites from 15102 and troctolites from 15302 are lower in KREEP than are Apollo 12 or 14 norites. A possible progenitor of KREEP-rich norite breccias has been found: a mesostasis-rich basalt from 15272 high in KREEP-related elements, but very low in the siderophiles Ir, Re, Au, Sb, and Ge, and hence lacking the ancient meteoritic component that occurs in all lunar norites. At least two varieties of ancient meteoritic component are present in the soil separates from this site, consistent with the complex impact history of the Pre-Imbrian surface.

Morgan, J. W.↗