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NASA NTRS2010

Isotopic Fractionation in Comets: Quantifying the Contribution of Interstellar Chemistry

Anomalously fractionated isotopic material is found in many primitive Solar System objects, such as meteorites and comets. It is thought, in some cases, to trace interstellar matter that was incorporated into the Solar Nebula without undergoing significant processing. We will present the results of models of the nitrogen, oxygen, and carbon fractionation chemistry in dense molecular clouds, particularly in cares where substantial freeze-taut of molecules on to dust has occurred. The range of fractionation ratios expected in different interstellar molecules will be discussed and compared to the ratios measured in molecular clouds, comets and meteoritic material. These models make several predictions that can be tested in the near future by molecular line observations, particularly with the GBT.

Charnley, Steven↗
NASA NTRS2018

Isotopic Fractionation in Interstellar Chemistry

Anomalously fractionated isotopic material is found in many primitive Solar System objects, such as meteorites and comets. It is thought, in some cases, to trace interstellar matter that was incorporated into the Solar Nebula without undergoing significant processing. We will review observations and models of the nitrogen, oxygen, and carbon fractionation chemistry in dense molecular clouds. The range of fractionation ratios expected in different interstellar molecules will be discussed and compared to the ratios measured in molecular clouds, comets and meteoritic material.These studies make several predictions that can be tested by high-resolution molecular line observations with ALMA (Atacama Large Millimeter Array).

Charnley, Steven B.↗
NASA NTRS1973

Studies related to the evolution of the lunar soil materials

Studies of the chemistry and morphology of the lunar samples are reported. The presence of fragments of plagoclase in the centers of the impact craters indicate that the glass spheres were derived by meteoritic impact from high velocity particles, while the glass was at high temperatures. From the study of the Apollo 16 samples, it is suggested that this material was formed in a hot impact ejecta blanket, or in an igneous environment, and later exposed to meteoritic impact. It is suggested that particles from Apollo 17 were formed in a cloud of siliceous vapors.

Carter, J. L.↗
NASA NTRSDate not supplied

Assessment of Pioneer Venus Entry Heating with Coupled Radiation and Ablation

The objective of this work is to reconstruct thermocouple temperature measurements taken at the stagnation point of the Pioneer Venus large probe using uncoupled and coupled ablation calculations. The time history of the large probe forebody entry heating was obtained from a trajectory-based analysis that employed a material response solver to model equilibrium and nonequilibrium ablation chemistry at the surface. In the uncoupled approach, equilibrium ablation chemistry was assumed in the material response calculations, but the material response outputs were not returned to the flowfield solver. Therefore, the effects of char and pyrolysis gas injection into the boundary layer due to ablation (e.g., convective blockage and radiative energy absorption) did not influence the flowfield solutions. In the coupled approach, nonequilibrium ablation chemistry was performed and the material response outputs were returned to the flowfield solver. Therefore, the effects of char and pyrolysis gas injection into the boundary layer were accounted for in the flowfield solutions. Both uncoupled and coupled approaches produced reconstructed temperatures that were within 10% of the flight measurements through the entry heat pulse, with the coupled results comparing more favorably with the measurements. Overall, the reconstructed thermocouple temperatures in this work significantly improved on the results of previous reconstructions for the large probe.

Jannuel V V Cabrera↗
NASA NTRS1993

Surface characterization of LDEF materials

The NASA Long Duration Exposure Facility (LDEF), a passive experimental satellite, was placed into low-Earth orbit by the Shuttle Challenger in Apr. 1984. The LDEF spent an unprecedented 69 months in space. The flight and recovery of the LDEF provided a wealth of information on the longterm space environmental effects of a variety of materials exposed to the low-Earth orbit environment. Surface characterization of LDEF materials included polymers, composites, thermal control paints, and aluminum. X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), scanning electron microscopy (SEM), and contact angle analysis were used to document changes in both the surface composition and surface chemistry of these materials. Detailed XPS analysis of the polymer systems, such as Kapton, polyimide polysiloxane copolymers, and fluorinated ethylene propylene thermal blankets on the backside of the LDEF revealed significant changes in both the surface composition and surface chemistry as a result of exposure to the low-Earth orbit environment. Polymer systems such as Kapton, polyimide polysiloxane copolymers, and polysulfone showed a common trend of decreasing carbon content and increasing oxygen content with respect to the control sample. Carbon 1s curve fit XPS analysis of the composite samples, in conjunction with SEM photomicrographs, revealed significant ablation of the polymer matrix resin to expose the carbon fibers of the composite during exposure to the space environment. Surface characterization of anodized aluminum tray clamps, which were located at regular intervals over the entire LDEF frame, provided the first results to evaluate the extent of contamination with respect to position on the LDEF. The XPS results clearly showed that the amount and state of both silicon and fluorine contamination were directly dependent upon the position of the tray clamp on the LDEF.

Wightman, J. P.↗
NASA NTRS1995

Mapping minerals, amorphous materials, environmental materials, vegetation, water, ice and snow, and other materials: The USGS tricorder algorithm

One of the challenges of Imaging Spectroscopy is the identification, mapping and abundance determination of materials, whether mineral, vegetable, or liquid, given enough spectral range, spectral resolution, signal to noise, and spatial resolution. Many materials show diagnostic absorption features in the visual and near infrared region (0.4 to 2.5 micrometers) of the spectrum. This region is covered by the modern imaging spectrometers such as AVIRIS. The challenge is to identify the materials from absorption bands in their spectra, and determine what specific analyses must be done to derive particular parameters of interest, ranging from simply identifying its presence to deriving its abundance, or determining specific chemistry of the material. Recently, a new analysis algorithm was developed that uses a digital spectral library of known materials and a fast, modified-least-squares method of determining if a single spectral feature for a given material is present. Clark et al. made another advance in the mapping algorithm: simultaneously mapping multiple minerals using multiple spectral features. This was done by a modified-least-squares fit of spectral features, from data in a digital spectral library, to corresponding spectral features in the image data. This version has now been superseded by a more comprehensive spectral analysis system called Tricorder.

Clark, Roger N.↗
NASA NTRS1993

Characteristics of an Elevated Temperature ALN Particulate Reinforced NiAl

High energy milling of NiAl in liquid nitrogen (cryomilling) leads to the formation of a discontinuously AlN particle reinforced aluminide which has shown good potential as a high strength oxidation resistant material. Experiments have demonstrated that cryomilling is repeatable, and materials with reproducible chemistries and mechanical properties result. Furthermore, it is possible to vary the AlN content through control of the milling parameters. Tensile creep as well as compressive creep testing has been undertaken on a lot of NiAl-AlN. While this material is weaker in tension than compression, the tensile strength is respectable: for example, the creep rupture life exceeds 2700 h at 1300 K, 50 MPa. Heat treatment of the particulate reinforced aluminide at 1600 K promotes AlN growth which weakens the material but does not change the deformation mechanism. Cyclic oxidation testing of lots of NiAl-AlN which were cryomilled with and without yttria reveal that Y2O3 promotes better oxidation resistance. However, the presence or absence of yttria had no affect on the mechanical properties.

Whittenberger, J. D.↗
NASA NTRS1994

The organic surface of 5145 Pholus: Constraints set by scattering theory

No known body in the Solar System has a spectrum redder than that of object 5145 Pholus. We use Hapke scattering theory and optical constants measured in this laboratory to examine the ability of mixtures of a number of organic solids and ices to reproduce the observed spectrum and phase variation. The primary materials considered are poly-HCN, kerogen, Murchison organic extract, Titan tholin, ice tholin, and water ice. In a computer grid search of over 10 million models, we find an intraparticle mixture of 15% Titan tholin, 10% poly-HCN, and 75% water ice with 10-micrometers particles to provide an excellent fit. Replacing water ice with ammonia ice improves the fits significantly while using a pure hydrocarbon tholin, Tholin alpha, instead of Titan tholin makes only modest improvements. All acceptable fits require Titan tholin or some comparable material to provide the steep slope in the visible, and poly-HCN or some comparable material to provide strong absorption in the near-infrared. A pure Titan tholin surface with 16-micrometers particles, as well as all acceptable Pholus models, fit the present spectrophotometric data for the transplutonian object 1992 QB(sub 1). The feasibility of gas-phase chemistry to generate material like Titan tholin on such small objects is examined. An irradiated transient atmosphere arising from sublimating ices may generate at most a few centimeters of tholin over the lifetime of the Solar System, but this is insignificant compared to the expected lag deposit of primordial contaminants left behind by the sublimating ice. Irradiation of subsurface N2/CH4 or NH3/CH4 ice by cosmic rays may generate approximately 20 cm of tholin in the upper 10 m of regolith in the same time scale but the identity of this tholin to its gas-phase equivalent has not been demonstrated.

Wilson, Peter D.↗
NASA NTRS1999

Chemistry Experiments

The purpose of the chemistry component of the model comparison is to assess to what extent differences in the formulation of chemical processes explain the variance between model results. Observed concentrations of chemical compounds are used to estimate to what degree the various models represent realistic situations. For readability, the materials for the chemistry experiment are reported in three separate sections. This section discussed the data used to evaluate the models in their simulation of the source gases and the Nitrogen compounds (NO(y)) and Chlorine compounds (Cl(y)) species.

Brasseur, Guy↗
NASA NTRS1975

The source and origin of the exotic component and KREEP-rich materials on the moon

The enrichments of trace-element concentrations in lunar soils are attributed to the combined effects of comminution of local rocks and a preferential addition of the exotic component to finer grain sizes. The exotic component appears similar to Fra Mauro materials, and there is a strong correlation between the percentage of exotic component and distance from the Fra Mauro site. Based on trace-element characteristics, it is suggested that the exotic component is finely comminuted KREEP and is dispersed on the lunar surface from the Fra Mauro and other high gamma-ray active regions in the Imbrium-Procellarum regions. The major and trace-element chemistry of these materials is considered to be due to impact melting of trace-element-rich accessory phases followed by variable dilution with partial melts of the bulk solid phases of plagioclase, low-Ca pyroxene, and olivine. The generation of KREEP and the exotic component is an impact-produced local process and need not imply a global occurrence of radioactive crust on the moon.

Murthy, V. R.↗
NASA NTRS2010

The Origins and Evolution of Molecules in Icy Solids

Astronomical observations of the past few decades have revealed the existence of a variety of molecules in extraterrestrial ices. These molecules include H2O, CO, and CO2, and organics such as CH4, CH30H, and C2H6. Some ices are dominated by polar molecules, while non-polar species appear to dominate others. Observations, mainly in the radio and IR regions, have allowed the inference of other solid-phase molecules whose formation remains difficult to explain by gas-phase chemistry alone. Several laboratory research groups have reported on extensive experiments on the solid-phase reaction chemistry of icy materials, generally as initiated by either ionizing radiation or vacuum-UV photons. These experiments not only permit molecular identifications to be made from astronomical observations, but also allow predictions of yet unidentified molecules. This laboratory approach has evolved over more than 30 years with much of the earliest work focusing on complex mixtures thought to represent either cometary or interstellar ices. Although those early experiments documented a rich solid-state photo- and radiation chemistry, they revealed few details of reactions for particular molecules, partly due to the multi-component nature of the samples. Since then, model systems have been examined that allow the chemistry of individual species and specific reactions to be probed. Reactions involving most of the smaller astronomical molecules have now been studied and specific processes identified. Current laboratory work suggests that a variety of reactions occur in extraterrestrial ices, including acid-base processes, radical dimerizations, proton transfers, oxidations, reductions, and isomerizations. This workshop presentation will focus on chemical reactions relevant to solar system and interstellar ices. While most of the work will be drawn from that to which the speaker has contributed, results from other laboratories also will be included. Suggestions for future studies will be made, with an emphasis on some present deficiencies. The speaker's work has been generously supported by these NASA research programs: Cassini Data Analysis, Exobiology, Mars Fundamental Research, Outer Planets Research, Planetary Atmospheres, Planetary Geology and Geophysics, and the NASA Astrobiology Institute.

Hudson, Reggie L.↗
NASA NTRS2016

Measurements of Oxychlorine species on Mars

Mars landed and orbiter missions have instrumentation capable of detecting oxychlorine phases (e.g. perchlorate, chlorate) on the surface. Perchlorate (~0.6 wt%) was first detected by the Wet Chemistry Laboratory in the surface material at the Phoenix Mars Landing site. Subsequent analyses by the Thermal Evolved Gas Analyser aboard the same lander detected an oxygen release (~465°C) consistent with the thermal decomposition of perchlorate. Recent thermal analysis by the Mars Science Laboratory’s Sample Analysis at Mars instrument has also indicated the presence of oxychlorine phases (up to 1.2 wt%) in Gale Crater materials. Despite being at detectable concentrations, the Chemistry and Mineralogy (CheMin) X-ray diffractometer has not detected oxychlorine phases. This suggests that Gale Crater oxychlorine may exist as poorly crystalline phases or that perchlorate/chlorate mixtures exist, so that individual oxychlorine concentrations are below CheMin detection limits (~1 wt%). Although not initially designed to detect oxychlorine phases, reinterpretation of Viking Gas Chromatography/Mass Spectrometer data also suggest that oxychlorine phases are present in the Viking surface materials. Remote near-infrared spectral analyses by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument indicate that at least some martian recurring slope lineae (RSL) have spectral signatures consistent with the presence of hydrated perchlorates or chlorates during the seasons when RSL are most extensive. Despite the thermal emission spectrometer, Thermal Emission Imaging System, Observatoire pour la Minéralogie, l’Eau, les Glaces et l’Activité and CRISM detection of hundreds of anhydrous chloride (~10–25 vol%) deposits, expected associated oxychlorine phases (>5–10 vol%) have not been detected. Total Cl and oxychlorine data sets from the Phoenix Lander and the Mars Science Laboratory missions could be used to develop oxychlorine versus total Cl correlations, which may constrain oxychlorine concentrations at other locations on Mars by using total Cl determined by other missions (e.g. Viking, Pathfinder, MER and Odyssey). Development of microfluidic or ‘lab-on-a-chip’ instrumentation has the potential to be the next generation analytical capability used to identify and quantify individual oxychlorine species on future landed robotic missions to Mars.

Perchlorate↗
NASA NTRS2010

A Study on Advanced Lithium-Based Battery Cell Chemistries to Enhance Lunar Exploration Missions

NASAs Exploration Technology Development Program (ETDP) Energy Storage Project conducted an advanced lithium-based battery chemistry feasibility study to determine the best advanced chemistry to develop for the Altair Lunar Lander and the Extravehicular Activities (EVA) advanced Lunar surface spacesuit. These customers require safe, reliable batteries with extremely high specific energy as compared to state-of-the-art. The specific energy goals for the development project are 220 watt-hours per kilogram (Wh/kg) delivered at the battery-level at 0 degrees Celsius ( C) at a C/10 discharge rate. Continuous discharge rates between C/5 and C/2, operation between 0 and 30 C and 200 cycles are targeted. Electrode materials that were considered include layered metal oxides, spinel oxides, and olivine-type cathode materials, and lithium metal, lithium alloy, and silicon-based composite anode materials. Advanced cell chemistry options were evaluated with respect to multiple quantitative and qualitative attributes while considering their projected performance at the end of the available development timeframe. Following a rigorous ranking process, a chemistry that combines a lithiated nickel manganese cobalt oxide Li(LiNMC)O2 cathode with a silicon-based composite anode was selected as the technology that can potentially offer the best combination of safety, specific energy, energy density, and likelihood of success.

Reid, Concha M.↗
NASA NTRS1979

Non-flammable polyimide materials for aircraft and spacecraft applications

Recent developments in polyimide chemistry show promise for producing materials with very low flammability and a wide range of mechanical properties. Polyimide foams can be synthesized to provide fire safety without detectable formation of smoke or toxic byproducts below 204 C (400 F), thus avoiding an environment which is lethal to human habitation. This work has been and is currently being performed under development programs, the objective of which is to provide cost effective processes for producing thermally stable, polyimide flexible resilient foams, thermal-acoustical insulating materials, rigid low density foam panels, and high strength foam structures. The chemical and physical properties demonstrated by these materials represent a technological advancement in the art of thermally stable polyimide polymers which are expected to insure fire protection of structures and components used in air transportation and space exploration. Data compiled to date on thermal, physical and functional properties of these materials are presented.

Gagliani, J.↗
NASA NTRS2021

Calibration of the SHERLOC Deep Ultraviolet Fluorescence–Raman Spectrometer on the Perseverance Rover

We describe the wavelength calibration of the spectrometer for the scanning of habitable environments with Raman and luminescence for organics and chemicals (SHERLOC) instrument onboard NASA’s Perseverance Rover. SHERLOC utilizes deep ultraviolet Raman and fluorescence (DUV R/F) spectroscopy to enable analysis of samples from the Martian surface. SHERLOC employs a 248.6 nm deep ultraviolet laser to generate Raman-scattered photons and native fluorescence emission photons from near-surface material to detect and classify chemical and mineralogical compositions. The collected photons are focused on a charge-coupled device and the data are returned to Earth for analysis. The compact DUV R/F spectrometer has a spectral range from 249.9 nm to 353.6 nm (200 cm1 to 12, 000 cm1) (with a spectral resolution of 0.296 nm (40 cm1)). The compact spectrometer uses a custom design to project a high-resolution Raman spectrum and a low-resolution fluorescence spectrum on a single charge-coupled device. The natural spectral separation enabled by deep ultraviolet excitation enables wavelength separation of the Raman/fluorescence spectra. The SHERLOC spectrometer was designed to optimize the resolution of the Raman spectral region and the wavelength range of the fluorescence region. The resulting illumination on the charge-coupled device is curved, requiring a segmented, nonlinear wavelength calibration in order to understand the mineralogy and chemistry of Martian materials.

Kyle Uckert↗
NASA NTRSDate not supplied

Bio-inspired Surface Structures to Mitigate Interfacial Particle Adhesion and Erosion - A Review

Lunar dust known as regolith is a huge challenge for lunar exploration missions. Formed over millennia by a complex process involving impacts of meteoroids and micrometeoroids on the lunar surface, lunar dust is porous, highly abrasive with sharp jagged edges, chemically reactive, electrostatically charged and sometimes magnetic. The chemical composition and thickness of the dust layer also varies in different regions of the lunar surface. From samples obtained by previous lunar missions, the average particle size is below 100 microns. This dust has the tendency to strongly adhere to any exposed surfaces, and often degrades the material functionality to eventually cause failure. Any material on the lunar surface is also subject to harsh temperature cycles ranging from -178 ̊C to + 123 ̊C and extreme ultraviolet radiation. While on the lunar surface, different classes of materials would be required for different applications. Advanced materials have been and will be used throughout the lunar lander, habitat, and mission equipment. Examples include: polymeric materials for astronaut protective clothing; metals and ceramics for the lunar lander legs and habitats, and excavating equipment; and semiconductors for solar panels and on-board electronics. In all these applications, the surfaces of the materials are expected or understood to be exposed to the extreme lunar environment condition that includes the regolith dust. During the Apollo missions, the dust clung to and abraded the astronaut’s suits, degraded seals, optics, clogged sensors and reduced performance of thermal radiators. The lunar dust adheres to the surface by various mechanisms, which include electrostatic and Coulombic interactions, Van-der-Waals forces, magnetic forces, mechanical interlocking, chemical bonding and donor-acceptor interactions. There are three primary strategies for developing technologies to minimize the lunar dust adhesion: active, passive and a combination of active and passive. In the active approach, an external energy is needed to prevent or remove particles from collecting on the surface. Mechanically powered brushes and electrodynamic dust screens are two examples. In the passive approach, no external power is needed, and the material surface properties are able to mitigate dust adhesion. A well-known example of this strategy is the low work function coatings for non-stick surfaces. In most cases a combination of active and passive methods might be needed to optimally manage the lunar regolith. The passive method is significantly more attractive as it does not require any external power or an additional control subsystem. These approaches optimize the mission payload and reduce risk. Surface modification to minimize the dust adhesion is thus very important to lunar missions. Here, naturally evolved surface structures might provide guidance for solutions. There are several factors that have to be considered for minimizing particle adhesion to a surface. These include the substrate material properties, surface topography, chemistry, and the characteristics of the adhering particles. When engineering a surface, the substrate material chosen would be dependent on the needs of the application. Tailoring the surface microstructure or chemistry opens up more possibilities for its optimal utilization

Lunar Dust↗
NASA NTRS1981

Infrared absorption spectra of metal carbides, nitrides and sulfides

The infrared absorption spectra of 12 kinds of metal carbides, 11 kinds of nitrides, and 7 kinds of sulfides, a total of 30 materials, were measured and the application of the infrared spectra of these materials to analytical chemistry was discussed. The measurements were done in the frequency (wave length) range of (1400 to 400/cm (7 to 25 mu). The carbides Al4C3, B4C, the nitrides AlN, BN, Si3N4, WB, and the sulfides Al2S3, FeS2, MnS, NiS and PbS were noted to have specific absorptions in the measured region. The sensitivity of Boron nitride was especially good and could be detected at 2 to 3 micrograms in 300 mg of potassium bromide.

Kammori, O.↗