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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

Intraspecific differences in bacterial responses to modelled reduced gravity

AIMS: Bacteria are important residents of water systems, including those of space stations which feature specific environmental conditions, such as lowered effects of gravity. The purpose of this study was to compare responses with modelled reduced gravity of space station, water system bacterial isolates with other isolates of the same species. METHODS AND RESULTS: Bacterial isolates, Stenotrophomonas paucimobilis and Acinetobacter radioresistens, originally recovered from the water supply aboard the International Space Station (ISS) were grown in nutrient broth under modelled reduced gravity. Their growth was compared with type strains S. paucimobilis ATCC 10829 and A. radioresistens ATCC 49000. Acinetobacter radioresistens ATCC 49000 and the two ISS isolates showed similar growth profiles under modelled reduced gravity compared with normal gravity, whereas S. paucimobilis ATCC 10829 was negatively affected by modelled reduced gravity. CONCLUSIONS: These results suggest that microgravity might have selected for bacteria that were able to thrive under this unusual condition. These responses, coupled with impacts of other features (such as radiation resistance and ability to persist under very oligotrophic conditions), may contribute to the success of these water system bacteria. SIGNIFICANCE AND IMPACT OF THE STUDY: Water quality is a significant factor in many environments including the ISS. Efforts to remove microbial contaminants are likely to be complicated by the features of these bacteria which allow them to persist under the extreme conditions of the systems.

Non-NASA Center↗
NASA NTRS2012

Survival of B. Horneckiae Spores Under Ground-simulated Space Conditions

To prevent forward contamination and maintain the scientific integrity of future life detection missions, it is important to characterize and attempt to eliminate terrestrial microorganisms associated with exploratory spacecraft and landing vehicles. Among the organisms isolated from spacecraft-associated habitats, spore-forming microbes are highly resistant to various physical and chemical conditions, which include ionizing and UV radiation, desiccation and oxidative stress, and the harsh environment of outer space or planetary surfaces. Recently a radiation resistant, spore forming bacterial isolate, Bacillus horneckiae, was isolated from a clean room of the Kennedy Space Center where the Phoenix spacecraft was assembled. The exceptionally high tolerance of extreme conditions demonstrated by sporeforming bacteria highlighted the need to assess the viability of these microbes in situ (in real) space. The proposed BOSS (Biofilm Organisms Surfing Space) project aims to understand the mechanisms by which biofilm forming organisms, such as B. horneckiae, will potentially be able to withstand harsh space conditions. As previously stated, the spore producing ability of these species gives them increased survivability to harsh conditions. Some of the spores will have the protective exosporium layer artificially removed before the test to determine if the existence of this layer significantly changes the survivability during the mission. In preparation for that experiment, we analyzed spores which were exposed during a ground simulation, the EXPOSE R2 Biofilm Organisms Surfing Space (BOSS). Previous to exposure, spores were deposited onto spacecraft grade aluminum coupons in a spore suspension calculated to contain between 10(exp 7) and 10(exp 8) spores. This precursor series will be used to establish a baseline survivability function for comparison with the future flight tests during EXPOSE-R. For each coupon, a 10% polyvinyl alcohol (PVA) film was applied and peeled from the coupon to recover the spores. One hundred μl of sterile 10% PVA was applied to the surface of the coupon and allowed to dry for 1 hour at 37 C. The films were then removed using sterile scalpel and forceps and placed into a glass test tube containing 2 milliliters of sterile deionized water. The PVA film process was then repeated on each coupon one additional time to ensure recovery of the majority of spores. The second PVA film was added in the same glass tube as in the previous round. If the spores remained 100% viable, the test tubes should now contain between 5 X 10(exp 6) and 5 X 10(exp 7) spores per millimeter; however, it is expected that some loss of viability has occurred. In order to assess this loss, the number of colony forming, viable spores was counted. To count the colony forming units (CFUs), the spore containing solution was diluted in a process of 10-fold serial dilution by mixing successive solutions in a 100 microliter spore suspension to 900 microliter deionized H2O ratio. A sample dilution series revealed that 10(exp -3) and 10(exp -4) concentrations would be necessary for an accurate CFU count to be taken. For those two concentrations, a spread on a TSA plate was prepared and incubated at 32 C. For the samples exposed to UV radiation, the cell survivability was too low to establish a count from 100 microliter spread plating. Instead, no dilutions were performed and the entire 2 milliliter spore suspension was plated and incubated at 32 C. The plate's CFU counts were taken at 24 hours and 48 hours from the time of plating. At the end of the CFU counting the total surviving spores in each sample were calculated based on the number of CFUs that were observed per 100 microliters, or per 2 milliliters for the UV irradiated samples. The results of these calculations are shown in Figures 1 and 2.

cleanroom↗
NASA NTRS2019

Ready for Our Trip to Mars? Turning the Red Planet Blue

Mars exploration is one of the major current scientific breakthroughs. NASA is actively developing its Mars Exploration Program through several rovers and orbiters to better understand the origin and current conditions of the Red Planet. Since Mars is more Earth-like than any other planet, understanding its formation and evolution could enable to better understand our own origin. Mars is also considered as a future destination for survival of humankind, assuming our ability to face remaining technical challenges, such as radiation risks, extreme conditions, food and medicine supplies. The recent evidence of liquid water on Mars suggests that life could exist, and will be seeked by NASA Mars 2020 rover. Thus, Mars exploration opens remarkable perspectives towards the discovery of new resources and the humanity's expansion. But this tremendous potential also implies completely new questions: what will happen to the Earth if humans are able to escape from global warming and pollution? How will the Martian land be shared between Nations? Will it be impacted by political conflicts on the Earth? If life exists on Mars, will it be compatible with humans? As we get closer to Mars colonization every day, these questions should be addressed and considered as a new chance to envision a world that could benefit from the lessons of History. So, in addition to technical and scientific progress, Mars exploration gives us the chance to redefine our society as a whole.

societal impacts↗
NASA NTRS2016

The Effects of Hygrothermal Aging on the Impact Penetration Resistance of Triaxially Braided Composites

An experimental study was conducted to measure the effects of long term hygrothermal aging on the impact penetration resistance of triaxially braided polymer composites. Flat panels of three different materials were subjected to repeated cycles of high and low temperature and high and low humidity for two years. Samples of the panels were periodically tested under impact loading during the two year time period. The purpose of the study was to identify and quantify any degradation in impact penetration resistance of these composites under cyclic temperature and humidity conditions experienced by materials in the fan section of commercial gas turbine engines for a representative aircraft flight cycle. The materials tested consisted of Toray ® T700S carbon fibers in a 2D triaxial braid with three different resins, Cycom® PR520, a toughened resin, Hercules® 3502, an untoughened resin and EPON 862, intermediate between the two. The fiber preforms consisted of a quasi-isotropic 0/+60/-60 braid with 24K tows in the axial direction and 12K tows in the bias directions. The composite panels were manufactured using a resin transfer molding process producing panels with a thickness of 0.125 inches. The materials were tested in their as-processed condition and again after one year and two years of aging (1.6 years in the case of E862). The aging process involved subjecting the test panels to two cycles per day of high and low temperature and high and low humidity. A temperature range of -60degF to 250degF and a humidity range of 0 to 85% rh was used to simulate extreme conditions for composite components in the fan section of a commercial gas turbine engine. Additional testing was conducted on the as-processed PR520 composite under cryogenic conditions. After aging there was some change in the failure pattern, but there was no reduction in impact penetration threshold for any of the three systems, and in the case of the 3502 system, a significant increase in penetration threshold. There was also an increase in the penetration resistance of the PR520 system impacted under cryogenic conditions.

composite↗
NASA NTRS1994

Degassing mechanisms of noble gases from carbonado diamonds

Diamonds are unique samples for inferring ancient mantle conditions, because of their enormous stability, antiquity and also of mantle origin. However, as temperatures in the mantle where diamonds have existed are very high (greater than 1000 C) and residence time of some diamonds could be more than a few billion years, it is imperative to examine whether or not diamonds have retained their pristine characteristics, especially those of noble gases, under such extreme conditions. As discussed in a review article by Ozima, there are rather large variations in the diffusivity of helium in diamonds obtained in the early determinations. The data are also limited to temperatures higher than 1200 C. In the present study, we conducted more refined diffusion experiments for He using carbonado diamonds, which have large amounts of radiogenic (4)He approximately 10(exp -2) cu cm STP/g. On the basis of the experimentally estimated diffusion coefficients, we will discuss retentivity of He in diamonds in the mantle condition.

Zashu, S.↗
NASA NTRS1993

Abrupt climate change and transient climates during the Paleogene: a marine perspective

Detailed investigations of high latitude sequences recently collected by the Ocean Drilling Program (ODP) indicate that periods of rapid climate change often culminated in brief transient climates, with more extreme conditions than subsequent long term climates. Two examples of such events have been identified in the Paleogene; the first in latest Paleocene time in the middle of a warming trend that began several million years earlier: the second in earliest Oligocene time near the end of a Middle Eocene to Late Oligocene global cooling trend. Superimposed on the earlier event was a sudden and extreme warming of both high latitude sea surface and deep ocean waters. Imbedded in the latter transition was an abrupt decline in high latitude temperatures and the brief appearance of a full size continental ice-sheet on Antarctica. In both cases the climate extremes were not stable, lasting for less than a few hundred thousand years, indicating a temporary or transient climate state. Geochemical and sedimentological evidence suggest that both Paleogene climate events were accompanied by reorganizations in ocean circulation, and major perturbations in marine productivity and the global carbon cycle. The Paleocene-Eocene thermal maximum was marked by reduced oceanic turnover and decreases in global delta 13C and in marine productivity, while the Early Oligocene glacial maximum was accompanied by intensification of deep ocean circulation and elevated delta 13C and productivity. It has been suggested that sudden changes in climate and/or ocean circulation might occur as a result of gradual forcing as certain physical thresholds are exceeded. We investigate the possibility that sudden reorganizations in ocean and/or atmosphere circulation during these abrupt transitions generated short-term positive feedbacks that briefly sustained these transient climatic states.

NASA Program Exobiology↗
NASA NTRS1985

Development of powder metallurgy 2XXX series Al alloy plate and sheet materials for high temperature aircraft structural applications, FY 1983/1984

The objective of this investigation is to fabricate and evaluate PM 2124 Al alloy plate and sheet materials according to NASA program goals for damage tolerance and fatigue resistance. Previous research has indicated the outstanding strength-toughness relationship available with PM 2124 Al-Zr modified alloy compositions in extruded product forms. The range of processing conditions was explored in the fabrication of plate and sheet gage materials, as well as the resultant mechanical and metallurgical properties. The PM composition based on Al-3.70 Cu-1.85 Mg-0.20 Mn with 0.60 wt. pct. Zr was selected. Flat rolled material consisting of 0.250 in. thick plate was fabricated using selected thermal mechanical treatments (TMT). The schedule of TMT operations was designed to yield the extreme conditions of grain structure normally encountered in the fabrication of flat rolled products, specifically recrystallized and unrecrystallized. The PM Al alloy plate and sheet materials exhibited improved strength properties at thin gages compared to IM Al alloys, as a consequence of their enhanced ability to inhibit recrystallization and grain growth. In addition, the PM 2124 Al alloys offer much better combinations of strength and toughnessover equivalent IM Al. The alloy microstructures were examined by optical metallographic texture techniques in order to establish the metallurgical basis for these significant property improvements.

Chellman, D. J.↗
NASA NTRS1988

Energy and mass balance in the three-phase interstellar medium

Details of the energy and mass balances are considered in the context of a three-phase interstellar medium. The rates of mass exchange between the different phases are derived based on the pressure variations created by supernova remnant expansions. It is shown that the pressure-confined warm and cold gases have stable temperatures under a variety of interstellar conditions. The three-phase quasi-static configuration is found to be a natural outcome, and both warm and cold phases generally contribute about half of the total mass density to the diffuse interstellar gas. The model is also likely to be self-regulatory in the sense that variations of the input parameters do not strongly alter the general result, which is consistent with most current observations. The consequences of extreme conditions on this model are considered, and the possible implications for interstellar medium in other galaxies are briefly discussed.

Wang, Zhong↗
NASA NTRS2020

Machiite, Al2Ti3O9, A New Oxide Mineral from the Murchison Carbonaceous Chondrite: A New Ultra-refractory Phase From the Solar Nebula

Machiite (IMA 2016-067), Al2Ti3O9, is a new mineral that occurs as a single euhedral crystal, 4.4 mm in size, in contact with an euhedral corundum grain, 12 mm in size, in a matrix of the Murchison CM2 carbonaceous chondrite. The mean chemical composition of holotype machiite by electron probe microanalysis is (wt%) TiO2 59.75, Al2O3 15.97, Sc2O3 10.29, ZrO2 9.18, Y2O3 2.86, FeO 1.09, CaO 0.44, SiO2 0.20, MgO 0.10, total 99.87, giving rise to an empirical formula (based on 9 oxygen atoms pfu) of (Al1.17Sc0.56Y0.10Ti4+0.08Fe0.06Ca0.03Mg0.01)(Ti4+2.71Zr0.28Si0.01)O9. The general formula is (Al,Sc)2(Ti4+,Zr)3O9. The end-member formula is Al2Ti3O9. Machiite has the C2/c schreyerite-type structure with a = 17.10 Å, b = 5.03 Å, c = 7.06 Å, b = 107°, V = 581 Å3, and Z = 4, as revealed by electron backscatter diffraction. The calculated density using the measured composition is 4.27 g/cm3. The machiite crystal is highly 16O-depleted relative to the coexisting corundum grain (D17O = –0.2 ± 2.4‰ and –24.1 ± 2.6‰, respectively; where D17O = d17O – 0.52 × d18O). Machiite is a new member of the schreyerite (V2Ti3O9) group and a new Sc,Zr-rich ultrarefractory phase formed in the solar nebula, either by gas-solid condensation or as a result of crystallization from a Ca,Al-rich melt having solar-like oxygen isotopic composition (D17O ~ –25‰) under high-temperature (~1400–1500 °C) and low-pressure (~10-4–10-5 bar) conditions in the CAI-forming region near the protosun. The currently observed disequilibrium oxygen isotopic composition between machiite and corundum may indicate that machiite subsequently experienced oxygen isotopic exchange with a planetary-like 16O-poor gaseous reservoir either in the solar nebula or on the CM chondrite parent body. The name machiite is in honor of Chi Ma, mineralogist at California Institute of Technology, for his contributions to meteorite mineralogy and discovery of many new minerals representing extreme conditions of formation.

Alexander N Krot↗
NASA NTRS2020

Machiite, Al2Ti3O9, a New Oxide Mineral from the Murchison Carbonaceous Chondrite: A New Ultra-refractory Phase from the Solar Nebula

Machiite (IMA 2016-067), Al2Ti3O9, is a new mineral that occurs as a single euhedral crystal, 4.4 mm in size, in contact with an euhedral corundum grain, 12 mm in size, in a matrix of the Murchison CM2 carbonaceous chondrite. The mean chemical composition of holotype machiite by electron probe microanalysis is (wt%) TiO2 59.75, Al2O3 15.97, Sc2O3 10.29, ZrO2 9.18, Y2O3 2.86, FeO 1.09, CaO 0.44, SiO2 0.20, MgO 0.10, total 99.87, giving rise to an empirical formula (based on 9 oxygen atoms pfu) of (Al1.17Sc0.56Y0.10Ti4+0.08Fe0.06Ca0.03Mg0.01)(Ti4+2.71Zr0.28Si0.01)O9. The general formula is (Al,Sc)2(Ti4+,Zr)3O9. The end-member formula is Al2Ti3O9. Machiite has the C2/c schreyerite-type structure with a = 17.10 Å, b = 5.03 Å, c = 7.06 Å, b = 107°, V = 581 Å3, and Z = 4, as revealed by electron backscatter diffraction. The calculated density using the measured composition is 4.27 g/cm3. The machiite crystal is highly 16O-depleted relative to the coexisting corundum grain (D17O = –0.2 ±2.4‰ and –24.1 ± 2.6‰, respectively; where D17O = d17O – 0.52 ×d18O). Machiite is a new member of the schreyerite (V2Ti3O9) group and a new Sc,Zr-rich ultrarefractory phase formed in the solar nebula, either by gas-solid condensation or as a result of crystallization from a Ca, Al-rich melt having solar-like oxygen isotopic composition (D17O ~ –25‰) under high-temperature (~1400–1500 °C) and low-pressure (~10-4–10-5 bar) conditions in the CAI-forming region near the protosun. The currently observed disequilibrium oxygen isotopic composition between machiite and corundum may indicate that machiite subsequently experienced oxygen isotopic exchange with a planetary-like 16O-poor gaseous reservoir either in the solar nebula or on the CM chondrite parent body. The name machiite is in honor of Chi Ma, mineralogist at California Institute of Technology, for his contributions to meteorite mineralogy and discovery of many new minerals representing extreme conditions of formation.

Machiite↗
NASA NTRS2005

Experiences issues with plastic parts at cold temperatures

Missions to MARS/planets/asteroids require electronic parts to operate and survive at extreme cold conditions. At extreme cold temperatures many types of cold related failures can occur. Office 514 is currently evaluating plastic parts under various cold temperature conditions and applications. Evaluations, screens, and qualifications are conducted on flight parts.

cold temperatures↗
NASA NTRS1947

Altitude-Wind-Tunnel Investigation of R-4360-18 Power-Plant Installation for XR60 Airplane: Performance of Induction and Exhaust Systems - 3

A study has been made of the performance of the induction and the exhaust systems on the XR60 power-plant installation as part of an investigation conducted in the Cleveland altitude wind tunnel. Altitude flight conditions from 5000 to 30,000 feet were simulated for a range of engine powers from 750 to 3000 brake horsepower. Slipstream rotation prevented normal pressure recoveries in the right side of the main duct in the region of the right intercooler cooling-air duct inlet. Total-pressure losses in the charge-air flow between the turbosupercharger and the intercoolers were as high as 2.1 inches of mercury. The total-pressure distribution of the charge air at the intercooler inlets was irregular and varied as much as 1.0 inch of mercury from the average value at extreme conditions, Total-pressure surveys at the carburetor top deck showed a variation from the average value of 0.3 inch of mercury at take-off power and 0.05 inch of mercury at maximum cruising power, The carburetor preheater system increased the temperature of the engine charge air a maximum of about 82 F at an average cowl-inlet air temperature of 9 F, a pressure altitude of 5000 feet, and a brake horsepower of 1240.

Dupree, David T.↗
NASA NTRS2017

Growth and Survival of Perchlorate-Reducing Bacteria in Media Containing Elevated Perchlorate Concentrations and UV-C Conditions

Introduction: The identification of perchlorate (ClO4(-)) on Mars has led to the possibility that complete redox couples are available for microbial metabolism in contemporary surface environments. Perchlorate-reducing bacteria (PRB) utilize ClO4(-) and chlorate (ClO3(-)) as terminal electron acceptors due to the high reduction potential. Additionally, ClO4(-) salts have been suggested as a possible source of brines on Mars and spectral evidence indicates that the hydration of ClO4(-) salts in the regolith of Martian is linked to the surface recurring slope lineae (RSL). For these reasons PRB may serve as analog organisms for possible life on Mars. However, there is very little information on the viability of PRB in aqueous environments that contain high levels of perchlorate Microorganisms on or near the surface of Mars, such as in the RSL, would potentially be exposed to high-salinity and high ultraviolet radiation environments. Under these extreme conditions, microorganisms must possess mechanisms for maintaining continued high genome fidelity. To assess possible microbial viability in contemporary Mars analog environments we are investigating the tolerance of two PRB strains in aqueous conditions under high UV-C conditions and high ClO4(-) concentrations.

Bywaters, K. F.↗
NASA NTRSDate not supplied

Validation of CrIS Ozone and Carbon Oxide Products from CrIS Single-Field-of-View Retrievals

Single Field-of-view Sounder Atmospheric Products (SiFSAP) from Cross-track Infrared Sounder (CrIS) on S-NPP have been developed at NASA Langley Research center, and recently a significant improvement in its trace gases products has been made. These products are derived based on the Principal Component (PC)-based Radiative Transfer Model (PCRTM) and an optimal estimation retrieval method (PCRTM-RA). Use of the PCRTM in this method allows for fast and accurate calculations for thousands of spectral channels under clear and cloudy sky conditions. The use of principal component to compress information from all spectral channels into the PC domain enables to reduce the observational noise and use the information from all hyperspectral infrared channels. The retrieval is made on PC-domain, and temperature, water vapor, trace gases, cloud and surface parameters are retrieved simultaneously. This presentation will present some validation to the SiFSAP ozone (O3) and carbon monoxide (CO) products. Since the SiFSAP has a spatial resolution of about 14 km at nadir, which is better than most global weather and climate models and enables to make process-oriented analysis of the transport of these gases, this study will focus on validation of CO and O3 products under some extreme weather and/or climate events, such as CO emission and transport from large biomass burning, and O3 variation impacted by fire emission, stratospheric intrusion, and tropical cyclones. Data used in our validation include CO and O3 from NASA aircraft campaigns, plus other satellite products such as CO and O3 from AIRS, IASI and TROPOMI, MOPPIT CO and OMPS O3. Some comparison of SiFSAP O3 with the O3 from the fifth-generation ECMWF reanalysis (ERA5) data the NASA Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2) will also present. Such a validation not only helps to quantify the performance of the retrievals in these extreme conditions, but also displays the capability of satellite observation to capture the fine-scale spatial pattern of CO and O3 variation.

Xiaozhen Xiong↗
NASA NTRS2023

Warming Overwhelms the Efficacy of Wet Conditions to Moderate Extreme Heat and Atmospheric Aridity Across the Central Plains

While the relationships between dry land surface conditions, heat, and aridity have been well-established, few studies have addressed whether global warming will affect the ability of wet conditions to moderate high temperatures and atmospheric aridity. Using Coupled Model Intercomparison Project Phase 6 models, we demonstrate that absolute changes in the monthly maximum temperature distribution during Central North American summers strongly outweigh the historical cooling effect of high precipitation and soil moisture conditions. Although wet conditions nearly always prevent concurrent extreme temperatures in the baseline period, these conditions are 40%–48% and 96%–98% less effective at 1 and 2° of global warming, respectively. However, high precipitation and soil moisture partially retain the ability to constrain concurrent high vapor pressure deficit conditions below historical thresholds at 1–2° of warming. Our results highlight the growing vulnerability of Central North America to warmer temperatures and drier atmospheric conditions, even during periods of high precipitation and soil moisture.

global warming↗
NASA NTRS1979

Wind study for high altitude platform design

An analysis of upper air winds was performed to define the wind environment at potential operating altitudes for high altitude powered platform concepts. Wind conditions of the continental United States, Pacific area (Alaska to Sea of Japan), and European area (Norwegian and Mediterranean Sea) were obtained using a representative network of sites selected based upon adequate high altitude sampling, geographic dispersion, and observed upper wind patterns. A data base of twenty plus years of rawinsonde gathered wind information was used in the analysis. Annual variations from surface to 10 mb pressure altitude were investigated to encompass the practical operating range for the platform concepts. Parametric analysis for the United States and foreign areas was performed to provide a basis for vehicle system design tradeoffs. This analysis of wind magnitudes indicates the feasibility of annual operation at a majority of sites and more selective seasonal operation for the extreme conditions between the pressure altitudes of 100 to 25 mb based upon the assumed design speeds.

High altitude powered platform studies↗
NASA NTRS1979

Wind study for high altitude platform design

An analysis of upper air winds was performed to define the wind environment at potential operating altitudes for high-altitude powered platform concepts. Expected wind conditions of the contiguous United States, Pacific area (Alaska to Sea of Japan), and European area (Norwegian and Mediterranean Seas) were obtained using a representative network of sites selected based upon adequate high-altitude sampling, geographic dispersion, and observed upper wind patterns. A data base of twenty plus years of rawinsonde gathered wind information was used in the analysis. Annual variations from surface to 10 mb (approximately 31 km) pressure altitude were investigated to encompass the practical operating range for the platform concepts. Parametric analysis for the United States and foreign areas was performed to provide a basis for vehicle system design tradeoffs. This analysis of wind magnitudes indicates the feasibility of annual operation at a majority of sites and more selective seasonal operation for the extreme conditions between the pressure altitudes of 100 to 25 mb based upon the assumed design speeds.

Strganac, T. W.↗
NASA NTRS2010

High Pressure/Temperature Metal Silicate Partitioning of Tungsten

The behavior of chemical elements during metal/silicate segregation and their resulting distribution in Earth's mantle and core provide insight into core formation processes. Experimental determination of partition coefficients allows calculations of element distributions that can be compared to accepted values of element abundances in the silicate (mantle) and metallic (core) portions of the Earth. Tungsten (W) is a moderately siderophile element and thus preferentially partitions into metal versus silicate under many planetary conditions. The partitioning behavior has been shown to vary with temperature, silicate composition, oxygen fugacity, and pressure. Most of the previous work on W partitioning has been conducted at 1-bar conditions or at relatively low pressures, i.e. <10 GPa, and in two cases at or near 20 GPa. According to those data, the stronger influences on the distribution coefficient of W are temperature, composition, and oxygen fugacity with a relatively slight influence in pressure. Predictions based on extrapolation of existing data and parameterizations suggest an increased pressured dependence on metal/ silicate partitioning of W at higher pressures 5. However, the dependence on pressure is not as well constrained as T, fO2, and silicate composition. This poses a problem because proposed equilibration pressures for core formation range from 27 to 50 GPa, falling well outside the experimental range, therefore requiring exptrapolation of a parametereized model. Higher pressure data are needed to improve our understanding of W partitioning at these more extreme conditions.

Shofner, G. A.↗