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Small inclusions (diameters ranging from 0.001 microns to 10 microns) of isotopically anomalous material within meteorites were almost certainly produced in mass-losing stars. These solid particles preserved their individual identities as they passed through the interstellar medium and the pre-solar nebular. The relationship between studies of meteorites and mass-losing red giants is explored.
Stratospheric mixing ratios of CH3D from 100 mb to 17mb (approximately equals 15 to 28 km)and HDO from 100 mb to 10 mb (approximately equals 15 to 32 km) have been inferred from high resolution solar occultation infrared spectra from the Atmospheric Trace MOlecule Spectroscopy (ATMOS) Fourier-transform interferometer. The spectra, taken on board the Space Shuttle during the Spacelab 3 and ATLAS-1, -2, and -3 missions, extend in latitude from 70 deg S to 65 deg N. We find CH3D entering the stratosphere at an average mixing ratio of (9.9 +/- 0.8) x 10(exp -10) with a D/H ratio in methane (7.1 +/- 7.4)% less than that in Standard Mean Ocean Water (SMOW) (1 sigma combined precision and systematic error). In the mid to lower stratosphere, the average lifetime of CH3D is found to be (1.19 +/- 0.02) times that of CH4, resulting in an increasing D/H ratio in methane as air 'ages' and the methane mixing ratio decreases. We find an average of (1.0 +/- 0.1) molecules of stratospheric HDO are produced for each CH3D destroyed (1 sigma combined precision and systematic error), indicating that the rate of HDO production is approximately equal to the rate of CH3D destruction. Assuming negligible amounts of deuterium in species other than HDO, CH3D and HD, this limits the possible change in the stratospheric HD mixing ratio below about 10 mb to be +/- 0.1 molecules HD created per molecule CH3D destroyed.
Recent analyses of the carbonate globules present in the Martian meteorite ALH84001 have detected polycyclic aromatic hydrocarbons (PAHs) at the ppm level. The distribution of PAHs observed in ALH84001 was interpreted as being inconsistent with a terrestrial origin and were claimed to be indigenous to the meteorite, perhaps derived from an ancient Martian biota. However, Becker et al., have examined PAHs in the Martian meteorite EETA79001, in several Antarctic carbonaceous chondrites and Antarctic Allan Hills Ice and detected many of the same PAHs found in ALH84001. The reported presence of L-amino acids of apparent terrestrial origin in the EETA79001 druse material, suggests that this meteorite is contaminated with terrestrial/extraterrestrial organics probably derived from Antarctic ice meltwater that had percolated through the meteorite. The detection of PAHs and L-amino acids in these Martian meteorites suggests that despite storage in the Antarctic ice, selective changes of certain chemical and mineralogical phases has occurred.
We have determined abundance ratios in the core of the Perseus Cluster for several elements. These ratios indicate a central dominance of Type 1a supernova (SN Ia) ejects similar to that found for A496, A2199 and A3571. Simultaneous analysis of ASCA spectra from SIS1, GIS2, and GIS3 shows that the ratio of Ni to Fe abundances is approx. 3.4 +/- 1.1 times solar within the central 4'. This ratio is consistent with (and more precise than) that observed in other clusters whose central regions are dominated by SN Ia ejecta. Such a large Ni overabundance is predicted by "convective deflagration" explosion models for SNe Ia such as W7 but is inconsistent with delayed detonation models. We note that with current instrumentation the Ni K(alpha) line is confused with Fe K(beta) and that the Ni overabundance we observe has been interpreted by others as an anomalously large ratio of Fe K(beta) to Fe K(alpha) caused by resonant scattering in the Fe K(alpha) line. We argue that a central enhancement of SN Ia ejecta and hence a high ratio of Ni to Fe abundances are naturally explained by scenarios that include the generation of chemical gradients by suppressed SN Ia winds or ram pressure stripping of cluster galaxies. It is not necessary to suppose that the intracluster gas is optically thick to resonant scattering of the Fe K(alpha) line.
Using different processing conditions, we disperse the single-walled carbon nanotube (SWNT) into the polymethyl methacrylate (PMMA) to form composites. In the melt-blended sample, the SWNTs originally semiconducting - became predominantly metallic after dispersion into the melt-blended composite. The interaction of the PMMA and SWNT is investigated by the polarized Raman studies. The structure changes in the PMMA and SWNT shows that the anisotropic interactions are responsible for SWNT electronic density of states (DOS) changes. The increased metallic SWNT percentage is confirmed by the conductivity and dielectric constant measurements .
Combustion of solid fuel particles has many important applications, including power generation and space propulsion systems. The current models available for describing the combustion process of these particles, especially porous solid particles, include various simplifying approximations. One of the most limiting approximations is the lumping of the physical properties of the porous fuel with the heterogeneous chemical reaction rate constants [1]. The primary objective of the present work is to develop a rigorous modeling approach that could decouple such physical and chemical effects from the global heterogeneous reaction rates. For the purpose of validating this model, experiments with porous graphite particles of varying sizes and porosity are being performed under normal and micro gravity.
The effect of radiative feedback from the gas phase in micro-gravity combustion processes has been of increasing concern because of the implications in the selection and evaluation of appropriate fire suppressants. The use of CO2, an optically thick gas in the infrared region of the electromagnetic spectrum, has garnered widespread acceptance as an effective fire suppressant for most ground based applications. Since buoyant forces often dominate the flow field in 1-g environments the temperature field between the flame front and the fuel surface is not significantly affected by gas phase radiative absorption and re-emission as these hot gases are quickly swept downstream. However, in reduced gravity environments where buoyant-driven convective flows are negligible and where low-speed forced convective flows may be present at levels where gas phase radiation becomes important, then changes in environment that enhance gas phase radiative effects need to be better understood. This is particularly true in assessments of flammability limits and selection of appropriate fire suppressants for future space applications. In recognition of this, a ground-based investigation has been established that uses a droplet combustion configuration to systematically study the effects of enhanced gas phase radiation on droplet burn rates, flame structure, and radiative output from the flame zone.
Previous immunohistochemical studies combined with retrograde tracing in macaque monkeys have demonstrated that corticocortical projections can be differentiated by their content of neurofilament protein. The present study analyzed the distribution of nonphosphorylated neurofilament protein in callosally projecting neurons located at the V1/V2 border. All of the retrogradely labeled neurons were located in layer III at the V1/V2 border and at an immediately adjacent zone of area V2. A quantitative analysis showed that the vast majority (almost 95%) of these interhemispheric projection neurons contain neurofilament protein immunoreactivity. This observation differs from data obtained in other sets of callosal connections, including homotypical interhemispheric projections in the prefrontal, temporal, and parietal association cortices, that were found to contain uniformly low proportions of neurofilament protein-immunoreactive neurons. Comparably, highly variable proportions of neurofilament protein-containing neurons have been reported in intrahemispheric corticocortical pathways, including feedforward and feedback visual connections. These results indicate that neurofilament protein is a prominent neurochemical feature that identifies a particular population of interhemispheric projection neurons at the V1/V2 border and suggest that this biochemical attribute may be critical for the function of this subset of callosal neurons.
Enstatite chondrites (EC) contain highly reduced matrix minerals (e.g.- (Mg,Fe,Mn)S solid solution, CaS) that probably formed in thermodynamic equilibrium with a vapor phase. EC chondrules contain enstatite, Fs5 to Fs30, in which iron was reduced after formation, also by interaction with vapor [1, 2]. The origin and location of this reducing vapor bears upon the formation of the terrestrial planets (Mercury to Mars), the remnant chemical zoning of the asteroid belt (E, S, C, D-types), and the cosmochemistry of metals in the early solar system.
Stratospheric mixing of CH3D from 100 mb to 17 mb (?to 28 km) and HDO from 100 mb to 10.
Microgravity droplet combustion experiments were performed in elevated concentrations of CO2 at pressures of 1.0 atm, 3.0 atm, and 5.0 atm to examine the effects of a radiatively participating suppression agent in space applications. Methanol and n-heptane droplets, with an initial diameter of 2.0 mm supported on a quartz fiber, were used in these experiments. The ambient O2 concentration was held constant at 21% and the CO2 concentrations ranged from 0% to a maximum of 70%, by volume with the balance consisting of N2 . Results from the methanol tests showed slight decreases in burning rates with increased CO2 concentrations at all ambient pressures. The n-heptane tests show slight increases in burning rates with increasing CO2 concentrations at each pressure level. Instantaneous radiative heat flux was also measured using both a broadband radiometer (i.e., wavelengths from 0.6 microns to 40.0 microns) and a narrowband radiometer (i.e., centered at 5.6 microns with a filter width at half maximum of 1.5 microns). Radiative exchanges between the droplet and surrounding gases as well as the soot field produce departures from the classical quasisteady theory which would predict a decrease in burning rates with increasing CO2 concentrations in microgravity.
Martian meteorite Northwest Africa 5298 is a basaltic shergottite that was found near Bir Gandouz (Morocco). Its martian origin was confirmed by oxygen isotopes [1], as well as Mn/Fe ratios in the pyroxenes and K/anorthite ratios in the plagioclases [2]. Here we present a petrographic and geochemical study of NWA 5298. Comparison of mineralogical and geochemical characteristics of this meteorite with other Martian rocks shows that NWA 5298 is not likely paired with any other known shergottites, but it has similarities to another basaltic shergottite Dhofar 378.
An Information Architecture facilitates the understanding and, hence, harnessing of the human system risk-related data supply chain which enhances the ability to securely collect, integrate, and share data assets that improve human system research and operations. By mapping the risk-related data flow from raw data to useable information and knowledge (think of it as a data supply chain), the Human Research Program (HRP) and Space Life Science Directorate (SLSD) are building an information architecture plan to leverage their existing, and often shared, IT infrastructure.
The RESOLVE (Regolith and Environment Science and Oxygen and Lunar Volatile Extraction) project seeks to deploy a robotic ISRU lander at the lunar south pole to determine the accessibility of frozen ice and the resource potential at various locations. The OVEN (Oxygen and Volatiles Extraction Node) component will be used to heat samples to 150 C or higher in order to drive off ice and other volatiles, which will then be identified and measured. An ice volatilization system has been developed to specifically collect data on the extraction of water vapor from a sample. Testing of the system was begun in April of this year. This report addresses our current work to test the system in a relevant environment in this case, using simulants with up to 10wt% water ice at 76K, in reduced atmosphere.
Diffusive extinction of methanol droplets with initial diameters between 1.25 mm and 1.72 mm, burning in a quiescent microgravity environment at one atmosphere pressure, was obtained experimentally for varying levels of ambient carbon-dioxide concentrations with a fixed oxygen concentration of 21% and a balance of nitrogen. These experiments serve as precursors to those which are beginning to be performed on the International Space Station and are motivated by the need to understand the effectiveness of carbon-dioxide as a fire suppressant in low-gravity environments. In these experiments, the flame standoff distance, droplet diameter, and flame radiation are measured as functions of time. The results show that the droplet extinction diameter depends on both the initial droplet diameter and the ambient concentration of carbon dioxide. Increasing the initial droplet diameter leads to an increased extinction diameter, while increasing the carbon-dioxide concentration leads to a slight decrease in the extinction diameter. These results are interpreted using a critical Damk hler number for extinction as predicted by an earlier theory, which is extended here to be applicable in the presence of effects of heat conduction along the droplet support fibers and of the volume occupied by the support beads
The distribution and isotopic and enantiomeric compositions of amino acids found in three distinct fragments of the Tagish Lake C2-type carbonaceous chondrite were investigated via liquid chromatography fluorescence detection time-of-flight mass spectrometry and gas chromatography isotope ratio mass spectrometry. Large L-enantiomeric excesses (L(sub ee) approx. 43 to 59%) of the a-hydrogen aspartic and glutamic amino acids were measured in Tagish Lake, whereas alanine, another alpha-hydrogen protein amino acid, was found to be nearly racemic (D approx. L) using both techniques. Carbon isotope measurements of D- and L-aspartic acid and D- and L-alanine in Tagish Lake fall well outside of the terrestrial range and indicate that the measured aspartic acid enantioenrichment is indigenous to the meteorite. Alternate explanations for the Lexcesses of aspartic acid such as interference from other compounds present in the sample, analytical biases, or terrestrial amino acid contamination were investigated and rejected. These results can be explained by differences in the solid-solution phase behavior of aspartic acid, which can form conglomerate enantiopure solids during crystallization, and alanine, which can only form racemic crystals.
No abstract available
The Alpha Particle X-ray spectrometer (APXS) on the Curiosity rover in Gale Crater [1] is the 4th such instrument to have landed on Mars [2]. Along the rover's traverse down-section toward Glenelg (through sol 102), the APXS has examined four rocks and one soil [3]. Gale rocks are geochemically diverse and expand the range of Martian rock compositions to include high volatile and alkali contents (up to 3.0 wt% K2O) with high Fe and Mn (up to 29.2% FeO*).