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At least 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
NASA NTRS2006

Experimental Constraints on Ureilite Petrogenesis

This experimental study explores the petrogenesis of ureilites by a partial melting/smelting process. Experiments have been performed over temperature (1150-1280 C), pressure (5-12.5 MPa), and low oxygen fugacity (graphite-CO gas) conditions appropriate for a hypothetical ureilite parent body approximately 200 km in size. Experimental and modeling results indicate that a partial melting/smelting model of ureilite petrogenesis can explain many of the unique characteristics displayed by this meteorite group. Compositional information preserved in the pigeonite-olivine ureilites was used to estimate the composition of melts in equilibrium with the ureilites. The results of 20 experiments saturated with olivine, pyroxene, metal, and liquid with appropriate ureilite compositions are used to calibrate the phase coefficients and pressure-temperature dependence of the smelting reaction. The calibrated coefficients are used to model the behavior of a hypothetical residue that is experiencing fractional smelting. The residue is initially olivine-rich and smelting progressively depletes the olivine content and enriches the pyroxene and metal contents of the residues. The modeled residue composition at 1260 C best reproduces the trend of ureilite bulk compositions. The model results also indicate that as a ureilite residue undergoes isothermal decompression smelting over a range of temperatures, Ca/Al values and Cr203 contents are enriched at lower temperatures (below about 1240 C) and tend to decrease at higher temperatures. Therefore, fractional smelting can account for the high Ca/A1 and Cr203 wt% values observed in ureilites. We propose that ureilites were generated from an olivine-rich, cpx-bearing residue. Smelting began when the residue was partially melted and contained liquid, olivine, and carbon. These residues experienced varying degrees of fractional smelting to produce the compositional variability observed within the pigeonite-bearing ureilites. Variations in mineral composition, modal proportions, and isotopic signatures are best described by heterogeneous accretion of the ureilite parent body followed by minimal and variable degrees of igneous processing.

Singletary, Steven↗
NASA NTRS2004

Remote Sensing of the Haughton Impact Structure (HIS): A Terrestrial Proof of Concept for Using the Remote Sensing of Martian Craters as a Probe of Subsurface Composition

Impact cratering is the most widespread geological process in the Solar System. Impact craters can provide 'windows' into the subsurfaces of planetary bodies through excavation and uplift. By utilizing remote methods in the visible and near infrared (VNIR; 0.4-1.4 micron), short-wavelength infrared (SWIR; 1.4-2.5 micron) and thermal infrared (TIR 7-14 micron), subsurface mineral compositions may be identified and mapped via impact craters. Complex craters in particular, expose minerals from both the shallow and deep-seated subsurface, which may be identified spectroscopically. Complex craters have morphological features such as central peaks or peak rings, which are composed of relatively coherent lithologies tapped from deep-seated crustal components. While near-surface crustal components can be observed as coherent rocks uplifted and exposed in the rim and the crater walls, and from the ejecta deposits. Only two previously published studies using this approach have been successful on large planetary bodies. Tompkins and Pieters utilized ultraviolet and VNIR from Clementine to characterize near- and deep-subsurface materials in and around lunar craters. The work of Ramsey and Wright was the first remote spectroscopic study to successfully identify near-subsurface materials in the ejecta and crater wall of a terrestrial impact structure, namely Meteor Crater. Here we present early results of a third such study, a remote spectroscopy evaluation of the Haughton impact structure (HIS). The purpose of this study is to serve as terrestrial proof of concept that remote visible/infrared spectroscopic methods in this case, analysis of LANDSAT 7 ETM+ and ASTER data of the well-preserved HIS can be utilized in deciphering the subsurface composition of planetary crusts. This technique is particularly promising for Mars were limited tectonic uplift and ubiquitous dust-mantling offer few opportunities to access subsurface information.

Tornabene, L. L.↗
DOE OSTI2025

The variety and origin of materials accreted by Bennu’s parent asteroid

The first bodies to form in the Solar System acquired their materials from stars, the presolar molecular cloud and the protoplanetary disk. Asteroids that have not undergone planetary differentiation retain evidence of these primary accreted materials. However, geologic processes such as hydrothermal alteration can dramatically change their bulk mineralogy, isotopic compositions and chemistry. Here we analyse the elemental and isotopic compositions of samples from asteroid Bennu to uncover the sources and types of material accreted by its parent body. We show that some primary accreted materials escaped the extensive aqueous alteration that occurred on the parent asteroid, including presolar grains from ancient stars, organic matter from the outer Solar System or molecular cloud, refractory solids that formed close to the Sun, and dust enriched in neutron-rich Ti isotopes. We find Bennu to be richer in isotopically anomalous organic matter, anhydrous silicates, and light isotopes of K and Zn than its closest compositional counterparts, asteroid Ryugu and Ivuna-type (CI) carbonaceous chondrite meteorites. We propose that the parent bodies of Bennu, Ryugu and CI chondrites formed from a common but spatially and/or temporally heterogeneous reservoir of materials in the outer protoplanetary disk.

Kuiper belt↗
NASA NTRS2012

Complete Subsurface Elemental Composition Measurements With PING

The Probing In situ with Neutrons and Gamma rays (PING) instrument will measure the complete bulk elemental composition of the subsurface of Mars as well as any other solid planetary body. PING can thus be a highly effective tool for both detailed local geochemistry science investigations and precision measurements of Mars subsurface reSOurces in preparation for future human exploration. As such, PING is thus fully capable of meeting a majority of both ncar and far term elements in Challenge #1 presented for this conference. Measuring the ncar subsurface composition of Mars will enable many of the MEPAG science goals and will be key to filling an important Strategic Knowledge Gap with regard to In situ Resources Utilization (ISRU) needs for human exploration. [1, 2] PING will thus fill an important niche in the Mars Exploration Program.

Parsons, A. M.↗
NASA NTRS2004

Magnesium Isotopes in the Earth, Moon, Mars, and Pallasite Parent Body: High-Precision Analysis of Olivine by Laser-Ablation Multi-Collector ICPMS

Magnesium isotopes potentially offer new insights into a diverse range of processes including evaporation and condensation in the solar nebula, melting and metasomatism in planetary interiors, and hydrothermal alteration [1,2,3,4]. Volatility-related Mg isotopic variations of up to 10 per mil/amu relative to a terrestrial standard have been found in early nebular phases interpreted as evaporation residues [1], and relatively large variations (up to 3 per mil/amu) in the terrestrial mantle have been reported recently [4]. In order to investigate possible differences in the nebular history of material contributing to the terrestrial planets, and to search for evidence of a high-temperature origin of the Moon, we have measured the magnesium isotopic composition of primitive olivines from the Earth, Moon, Mars, and pallasite parent body using laser-ablation multicollector ICPMS.

Norman, M.↗
NASA NTRS1989

Dynamic mixing in magma bodies - Theory, simulations, and implications

The magma-mixing process is different from the mantle mixing process in that the mixing components of magma are dynamically active, with the melt density depending strongly on composition. This paper describes simulations of time-dependent variable-viscosity double-diffusive convection which were carried out to investigate quantitatively the mixing dynamics of magma in melt-dominated magma bodies. Results show that the dynamics of double-diffusive convection can impart complex patterns of composition, through time and space. The mixing time depends nonlinearly on many factors, including heat flux driving convection, the rate of diffusion of chemical species, the relative importance of thermal and chemical buoyancy, the viscosities of the mixing components, and the shape of the magma body.

Oldenburg, Curtis M.↗
NASA NTRS2023

Surface Volatile Composition as Evidence for Hydrothermal Processes Lasting Longer in Triton’s Interior than Pluto’s

Ocean worlds, or icy bodies in the outer solar system that have or once had subsurface liquid water oceans, are among the most compelling topics of astrobiology. Typically, confirming the existence of a subsurface ocean requires close spacecraft observations. However, combining our understanding of the chemistry that takes place in a subsurface ocean with our knowledge of the building blocks that formed potential ocean worlds provides an opportunity to identify tracers of endogenic activity in the surface volatiles of Pluto and Triton. We show here that the current composition of the volatiles on the surfaces and in the atmospheres of Pluto and Triton are deficient in carbon, which can only be explained by the loss of CH4 through a combination of aqueous chemistry and atmospheric processes. Furthermore, we find that the relative nitrogen and water abundances are within the range observed in building block analogs, comets, and chondrites. A lower limit for N/Ar in Pluto's atmosphere also suggests source building blocks that have a cometary or chondritic composition, all pointing to an origin for their nitrogen as NH3 or organics. Triton's lower abundance of CH4 compared to Pluto, and the detection of CO2 at Triton but not at Pluto points to aqueous chemistry in a subsurface ocean that was more efficient at Triton than Pluto. These results have applications to other large Kuiper Belt objects as well as the assessment of formation locations and times for the four giant planets given future probe measurements of noble gas abundances and isotope ratios.

Solar system formation↗
DOE OSTI2025

Microstructural, Oxidation, and Mechanical Behavior of NbTi-Based Refractory Alloys with 5 to 10 Pct Co, Cr, and Ni Additions

NbTi-based refractory alloys with additions of Co, Cr, and Ni represent an interesting medium-entropy alloy system with potential for protective oxide film formation, high strength, and ductility. This study investigates the microstructural evolution, oxidation behavior, and mechanical properties of NbTi-based alloys containing 5 to 10 at. pct Co, Cr, and Ni. CALPHAD predictions suggest that this composition range can be heat treated to obtain a predominantly body-centered cubic matrix phase. Mechanical properties, including microhardness, yield strength, maximum strength, and specific strength are evaluated through isothermal compression tests conducted between room temperature and 800 °C. The oxidation kinetics of these alloys are assessed through discontinuous oxidation tests. Parabolic oxidation kinetics were observed for NbTi–10Ni and NbTi–5Co, while linear oxidation kinetics were found for NbTi–10Cr and NbTi–10(CoCrNi). Microstructures and oxide layers are characterized using X-ray diffraction, electron backscatter diffraction, energy-dispersive X-ray spectroscopy, and scanning electron microscopy. All alloys exhibit significant mechanical softening between room temperature and 800 °C, with elastic-perfectly plastic flow observed at 800 °C. The addition of 10 pct Cr to NbTi resulted in two BCC phases up to 1050 °C, conflicting with CALPHAD predictions of a single-phase solid solution at this temperature, and resulting in higher flow stress at 800 °C. NbTi–10(CoCrNi) exhibited the lowest flow stress at 800 °C despite having more ‘cocktail effect’ potential and insufficient molar fractions of Co, Cr, or Ni to form a desirable protective oxide film.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Iron isotope fractionation between solid and liquid metal in the Fe-P±Ni system: Experimental constraints and implications for meteorites

Iron meteorites record a range of Fe isotope compositions that hold valuable information regarding the evolution of their parent bodies. Interpreting this isotopic variability, however, requires experimental constraints on the equilibrium isotope fractionation between phases. It is thought that the cores of many iron meteorite parent bodies experienced fractional crystallization, during which crystallization of solid iron-nickel occurs from an increasingly non-metal-rich liquid alloy. Phosphorus is one component of this alloy, and this study provides the first constraints on Fe-isotope fractionation between solid and liquid alloys in the Fe-Ni-P system. Experiments comprising Fe and P show a clear enrichment in the light isotopes of Fe in the liquid phase, which increases with the amount of phosphorus. Nickel-bearing samples are offset from the trend defined by Ni-free experiments, which is accounted for by the change in the solid alloy phase from a body-centered cubic to face-centered cubic structure upon the addition of Ni. The increasing light isotope enrichment of the liquid with increasing P content suggests interstitial solution of P, which is known to lengthen Fe-Fe bonds in Fe-P liquids (Waseda and Shiraishi 1977). Results suggest a negligible effect of P on Fe isotope fractionation during planetesimal core crystallization. Iron isotopes may, however, prove useful for identifying the petrogenesis of schreibersite in pallasites and iron meteorites.

58 GEOSCIENCES↗
NASA NTRS1972

NASTRAN: User experience with four example problems

Four different structural problems are solved to gain familiarity with the NASTRAN computer program. The problems are: (1) a simply-supported beam subjected to lateral loads, (2) a rotating filamentary composite bar under the action of centrifugal forces, (3) a missile body with aerodynamic, gravitational, and inertial forces, and (4) a square simply-supported plate with in-plane temperature changes capable of buckling the plate. Input and output data are given for each problem. The results are compared with those obtained by other methods. However, except for the examples employing beam elements in which the agreement is excellent, the element breakup chosen for convenience in obtaining program familiarity is too coarse to draw conclusions regarding the program accuracy. The example problems disclosed errors in the plotting and thermal-buckling routines of the program.

Rivello, R. M.↗
NASA NTRS1972

To develop a land use peak runoff classification system for highway engineering purposes

The author has identified the following significant results. Bands 6 and 7 are excellent for the detection of surficial water and swampy sites having the water table at or near the ground surface. Water bodies less than five acres in extent have been identified. Color composites should provide considerably more data for visual analysis than the black and white products currently available to this investigation.

Stoeckeler, E. G.↗
NASA NTRS1979

The condensation and fractionation of refractory lithophile elements

It is noted that Cr, Mg, and Si are fractionated in chondritic material along with, but to a lesser extent than, a large group of more refractory elements. These patterns are reexamined with the reasoning that this might imply some unique distribution at the time of fractionation. It is shown that apparently two distinct fractionization patterns can be resolved: one involving ordinary and enstatite chondrites and the other involving carbonaceous chondrites, the earth, the moon, and the eucrite parent body. It is noted that the two trends intersect at C1 composition. Attention is given to the range in which the largest fraction of planetary matter condenses. It is concluded that the appearance of large amounts of condensed materials is conceivably in some way related to the fractionization process, although the exact relationship cannot be specified.

Larimer, J. W.↗
NASA NTRS1984

Geometrically nonlinear analysis of laminated elastic structures

Laminated composite plates and shells that can be used to model automobile bodies, aircraft wings and fuselages, and pressure vessels among many other were analyzed. The finite element method, a numerical technique for engineering analysis of structures, is used to model the geometry and approximate the solution. Various alternative formulations for analyzing laminated plates and shells are developed and their finite element models are tested for accuracy and economy in computation. These include the shear deformation laminate theory and degenerated 3-D elasticity theory for laminates.

Reddy, J. N.↗
NASA NTRS1985

The partial volatilization of Mercury

During recent years research on the primitive solar nebula has followed two main themes: (1) Very early in the development of the nebula conditions probably favored the occurrence of major gaseous instabilities leading to the formation of giant gaseous protoplanets, but the rapid rise of the external temperature soon evaporated the envelopes of these protoplanets, possibly leaving behind precipitated solids which formed the cores and mantles of the terrestrial planets. (2) Models of the nebula indicate a later stage when conditions in the inner Solar System became very hot; at the position of Mercury the temperature was probably in the range 2500-3500 K. This leads to the hypothesis that the original protomercury was a body substantially more massive than the present planet and of normal composition, but that when it was immersed in the high-temperature field of the dissipating solar nebula, most of the rocky mantle was vaporized and mixed into the solar nebula gases and carried away by them. This hypothesis is investigated in the present paper. For simplicity the vaporization of a mantle composed of enstatite, MgSiO3, was computed for a planet with 2.25 the mass of Mercury at a temperature of 3000 K. It is argued that the mantle could probably be largely removed in the available time of 30,000 yrs. Subsequent accretion would restore some magnesium silicates to the mantle of the planet.

Cameron, A. G. W.↗
NASA NTRS1988

Sinker tectonics - An approach to the surface of Miranda

Two of the proposed explanations for the coronae seen on Miranda involve mantle convection driven by density anomalies. In the sinker model, the coronae result from late-accreting large silicate bodies slowly sinking through an icy mantle toward the body's center; in the riser model, they result from a compositionally produced, low-density, rising diapir. The present study determines the surface stresses induced by such density anomalies and the expected surface expressions. The results are in good agreement with the predictions of the sinker model.

Janes, D. M.↗
NASA NTRS1988

Recursive dynamics of topological trees of rigid bodies via Kalman filtering and Bryson-Frazier smoothing

The inverse and forward dynamics problems for a set of rigid bodies connected by hinges to form a topological tree are solved by using recursive techniques from linear filtering and smoothing theory. An inward filtering sequence computes a set of constraint moments and forces. This is followed by an outward sequence to determine a corresponding set of angular and linear accelerations. An inward sequence begins at the tips of all of the terminal bodies of the tree and proceeds inwardly through all of the branches until it reaches the root. Similarly, an outward sequence begins at the root and propagates to all of the tree branches until it reaches the tips of the terminal bodies. The paper also provides an approach to evaluate recursively the composite multibody system inertia matrix and its inverse.

Rodriguez, G.↗
NASA NTRS1999

Renal Stone Risk During Space Flight

Space flight produces a number of metabolic and physiological changes in the crewmembers exposed to microgravity. Following launch, body fluid volumes, electrolyte levels, and bone and muscle undergo changes as the human body adapts to the weightless environment. Changes in the urinary chemical composition may lead to the potentially serious consequences of renal stone formation. Previous data collected immediately after space flight indicate changes in the urine chemistry favoring an increased risk of calcium oxalate and uric acid stone formation (n = 323). During short term Shuttle space flights, the changes observed include increased urinary calcium and decreased urine volume, pH and citrate resulting in a greater risk for calcium oxalate and brushite stone formation (n = 6). Results from long duration Shuttle/Mir missions (n = 9) followed a similar trend and demonstrated decreased fluid intake and urine volume and increased urinary calcium resulting in a urinary environment saturated with the calcium stone-forming salts. The increased risk occurs rapidly upon exposure to microgravity, continues throughout the space flight and following landing. Dietary factors, especially fluid intake, or pharmacologic intervention can significantly influence the urinary chemical composition. Increasing fluid intake to produce a daily urine output of 2 liters/day may allow the excess salts in the urine to remain in solution, crystals formation will not occur and a renal stone will not develop. Results from long duration crewmembers (n = 2) who had urine volumes greater than 2.5 L/day minimized their risk of renal stone formation. Also, comparisons of stone-forming risk in short duration crewmembers clearly identified greater risk in those who produced less than 2 liters of urine/day. However, hydration and increased urine output does not correct the underlying calcium excretion due to bone loss and only treats the symptoms and not the cause of the increased urinary salts. Dietary modification and promising pharmacologic treatments may also be used to reduce the potential risk for renal stone formation. Potassium citrate is being used clinically to increase the urinary inhibitor levels to minimize the development of crystals and the growth of renal stones. Bisphosphonates are a class of drugs recently shown to help in patients with osteoporosis by inhibiting the loss of bones in elderly patients. This drug could potentially prevent the bone loss observed in astronauts and thereby minimize the increase in urinary calcium and reduce the risk for renal stone development. Results of NASA's renal stone risk assessment program clearly indicate that exposure to microgravity changes the urinary chemical environment such that there is an increased risk for supersaturation of stone-forming salts, including calcium oxalaie and brushite. These studies have indicated specific avenues for development of countermeasures for the increased renal stone risk observed during and following space flight. Increased hydration and implementation of pharmacologic countermeasures should largely mitigate the in-flight risk of renal stones.

Whitson, Peggy A.↗
NASA NTRS2001

Fabricating High Resolution Mirrors for Hand X-Ray Astronomy

We describe the fabrication process for producing high-resolution conical mirrors for hard x-ray astronomy. When flown aboard stratospheric balloons, these high-resolution reflective mirrors focus hard x-rays (10-70 keV) emitted from cosmic sources such as supernovae, neutron stars, and quasars onto imaging focal plane detectors. Focused hard x-ray images allow scientists to determine the elemental compositions, temperatures, magnetic fields, velocities, and gravitational fields of these celestial bodies. The fabrication process involves generating super-polished mandrels, mandrel metrology, mirror shell nickel electroforming, and mirror testing. Each mandrel is a cylinder consisting of two conical segments; each segment is approximately 305-mm long. Through precision grinding these mandrels before super polishing, we have achieved 30 arc seconds, half power diameter replicated mirrors. During a May 2001 high atmosphere balloon flight, these mirrors focused high energy x-rays from three different celestial sources. However, we seek to improve the angular resolutions of future mirror shells by a factor of two. To achieve this goal, we have begun single point diamond turning the mandrels before super polishing. This has allowed greater precision tolerances on mandrel surface roughness and axial figure errors before super polishing. Surface roughnesses before polishing have been reduced from approximately 60 nm to approximately 15 nm. The peak to valley axial figure profile errors have been reduced from approximately 1.0 micrometers to approximately 0.4 micrometers. We are currently in Phase 2 of the HERO (high energy replicated optics) program which entails the production of sixteen 6-m-focal-length mirror modules, each containing a nested array of 15 mirror shells of diameters ranging from 50-mm to 94-mm. This flight is slated for the fall of 2003.

Speegle, Chet O.↗