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NASA NTRS1997

Constraints on the Magnitude of Vertical and Lateral Mass Transport on the Moon

The role of vertical and lateral mass transport of crustal materials on the observed patterns of lunar surface composition, and the effects on our understanding of the geologic evolution of the planet, have been the subject of much debate in the lunar science community. The primary consensus that emerged from analyses of these processes in the 1970's and 1980's was that vertical and lateral mixing through impact gardening was a relatively inefficient process, and not likely to have contributed significantly to compositional units and variations on the Moon. The supporting evidence for this view is that unit boundaries (e.g. mare-highland contacts, contacts between mare color units) are still apparently quite distinct and sharp despite several aeons of impact activity, and cores from the Apollo landing sites did not show any evidence of widespread homogenization of the surface composition, nor distinct compositional gradients across geologic boundaries. In addition, modeling of vertical and lateral transport generally showed that the effects on composition should be confined to horizontal scales of about a kilometer and vertical scales of a meter. The problem with this consensus is that there is ample contradictory evidence. The fundamental discovery of Wood et al. (1970) was made possible by significant horizontal transport of highland material to the center of Mare Tranquillitatis. The continuous and discontinuous ejecta from the crater Copernicus has clearly influenced the surface composition of a large area of the lunar maria, while rays and ejecta from many highland craters are easily recognized in and around the nearside maria. Despite this contrary evidence, there have been few detailed studies to quantify the amount and rate of material redistribution through impact processes (a notable exception is reported in the paper by Pieters et al, 1985), largely because data adequate to critically analyze this process were lacking. However, the multispectral images acquired by the Galileo and Clementine missions now permit the investigation of this process.

Mustard, John F.↗

NASA NTRS2003

Spectral Properties of Hydrated Salts at Low Temperature: Implications for Europa Mission Spectrometer Design

Knowledge of the surface composition of Europa is critical for modeling of surface and interior processes and especially for evaluation of astrobiological potential. While much information has been derived from the Galileo Near-Infrared Mapping Spectrometer (NIMS) investigation, some breakthroughs have created more questions than answers. Any future Europa mission will attempt to capitalize on lessons learned from NIMS and try to answer these questions. At present, the surface composition appears to be a mixture of water ice, hydrated salts, sulfur compounds, radiolysis products (such as hydrogen peroxide and possibly simple organics like formaldehyde) and some as yet unidentified component. The small spatial scale of heterogeneity in Europa's surface geology poses additional challenges for orbiting spectrometers due to spectral mixing effects.

Dalton, J. Brad↗

NASA NTRS1976

The Surface Chemical Composition of Lunar Samples and Its Significance for Optical Properties

The surface iron, titanium, calcium, and silicon concentration in numerous lunar soil and rock samples was determined by Auger electron spectroscopy. All soil samples show a large increase in the iron to oxygen ratio compared with samples of pulverized rock or with results of the bulk chemical analysis. A solar wind simulation experiment using 2 keV energy alpha -particles showed that an ion dose corresponding to approximately 30,000 years of solar wind increased the iron concentration on the surface of the pulverized Apollo 14 rock sample 14310 to the concentration measured in the Apollo 14 soil sample 14163, and the albedo of the pulverized rock decreased from 0.36 to 0.07. The low albedo of the lunar soil is related to the iron + titanium concentration on its surface. A solar wind sputter reduction mechanism is discussed as a possible cause for both the surface chemical and optical properties of the soil.

Gold, T.↗

NASA NTRS1992

Workshop on Innovative Instrumentation for the In Situ Study of Atmosphere-Surface Interactions on Mars

The speakers in the first session of the workshop addressed some of the continuing enigmas regarding the atmospheric composition, surface composition, and atmosphere-surface interactions on Mars; provided a description of a database of proposed payloads and instruments for SEI missions that is scheduled to be accessible in 1993; discussed potential uses of atmospheric imaging from landed stations on Mars; and advocated the collection and employment of high-spectral-resolution reflectance and emission data.

Fegley, Bruce, Jr.↗

NASA NTRS1994

Surface ices in the outer solar system

Planetary volatile inventories are products of several factors: (1) condensation-accretion of pre-planetary material which determines the bulk volatile inventory; (2) energy history of a planet, including timing, causes, and mechanisms of degassing; (3) the volatile sinks, including temporary, long term, and permanent; and (4) external processes operating on the volatile inventory. Information regarding the current surface compositions provide insight into both internal and surface-atmosphere evolutionary history. Our discussion focuses upon the surface composition of outer solar system planets and satellites as determined by spacecraft and telescopic spectral observations. We provide a review and an update of the recent work by Cruikshank and Brown that includes more recent observations and interpretations. In the context of formation and evolution of solar system bodies, the interesting ices typically considered are simple molecules formed from elements having high cosmic abundances. These mainly include ices of H2O, NH3, SO2, H2S, CH4, CO, CO2, and N2. In the solid state, these ices have vibrational spectral features, analogous to their gaseous counterparts but rotational transitions are quenched, that lie in the near- and mid-infrared. The overtone and combination modes, occurring in the visible and near-IR region, are of particular importance as standard observational techniques used to identify these ices rely upon reflected solar energy. Table I summarizes the ices found on various bodies in the outer solar system. H2O is most abundant surface material in the inner and middle regions while more volatile species appear to dominate surfaces in the outermost edge of the outer solar system.

Roush, Ted L.↗

NASA NTRS1983

The diffusivity of hydrogen in Nb stabilized stainless steel

The evolution of hydrogen from 347 stainless steel has been studied by using a real time dynamic technique under ultrahigh vacuum conditions. Auger electron spectroscopy was used to determine the surface composition as a function of time and temperature. The surface film on the electropolished samples was found to be approximately 15 A thick and consisted of a carbon-oxygen complex and a metal oxide (FexOy). Upon heating to 400 C, the carbon-oxygen complex desorbed as CO and the remaining oxygen and carbon began to incorporate. Also at this temperature sulfur began to diffuse out of the bulk to the surface and at approximately 800 C formed a complete monolayer. At 900 C, carbon and oxygen virtually disappeared, leaving the monolayer of sulfur as the only surface contaminant. The hydrogen diffusivity was found to follow closely the equation D = 7.01 x 10 to the -7th exp(-48.0/RT) sq m per second over the entire temperature range studied, thus indicating that hydrogen evolution is not significantly affected by the changing surface composition. The somewhat higher value of the diffusivity obtained in this work compared to past measurements in austenitic stainless steels may indicate the importance of sample preprocessing and ultrahigh vacuum conditions in minimizing the effects of surface layers.

Outlaw, R. A.↗

NASA NTRS1984

Laboratory degradation of Kapton in a low energy oxygen ion beam

An atomic oxygen ion beam, accelerated from a tunable microwave resonant cavity, was used at Lewis Research Center to bombard samples of the widely used polyimide Kapton. The Kapton experienced degradation and mass loss at high rates, which may be comparable to those found in Space Shuttle operations if the activation energy supplied by the beam enabled surface reactions with the ambient oxygen. The simulation reproduced the directionality (ram-wake dependence) of the degradation, the change in optical properties of the degraded materials, and the structure seen in scanning electron micrographs of samples returned on the Shuttle Trails with a substituted argon ion beam produced no rapid degradation. Energy Dispersive X-ray Analysis (EDAX) showed significant surface composition changes in all bombarded samples. Mass loss rates and surface composition changes are discussed in terms of the possible oxidation chemistry of the interaction. Finally, the question of how the harmful degradation of materials in low Earth orbit can be minimized is addressed.

Ferguson, D. C.↗

NASA NTRS1983

Laboratory degradation of Kapton in a low energy oxygen ion beam

An atomic oxygen ion beam, accelerated from a tunable microwave resonant cavity, was used at Lewis Research Center to bombard samples of the widely used polyimide Kapton. The Kapton experienced degradation and mass loss at high rates, which may be comparable to those found in Space Shuttle operations if the activation energy supplied by the beam enabled surface reactions with the ambient oxygen. The simulation reproduced the directionality (ram-wake dependence) of the degradiation, the change in optical properties of the degraded materials, and the structure seen in scanning electron micrographs of samples returned on the Shuttle Trails with a substituted argon ion beam produced no rapid degradation. Energy Dispersive X-ray Analysis (EDAX) showed significant surface composition changes in all bombarded samples. Mass loss rates and surface composition changes are discussed in terms of the possible oxidation chemistry of the interaction. Finally, the question of how the harmful degradation of materials in low earth orbit can be minimized is addressed.

Ferguson, D. C.↗

NASA NTRS2012

Methods of Attaching or Grafting Carbon Nanotubes to Silicon Surfaces and Composite Structures Derived Therefrom

The present invention is directed toward methods of attaching or grafting carbon nanotubes (CNTs) to silicon surfaces. In some embodiments, such attaching or grafting occurs via functional groups on either or both of the CNTs and silicon surface. In some embodiments, the methods of the present invention include: (1) reacting a silicon surface with a functionalizing agent (such as oligo(phenylene ethynylene)) to form a functionalized silicon surface; (2) dispersing a quantity of CNTs in a solvent to form dispersed CNTs; and (3) reacting the functionalized silicon surface with the dispersed CNTs. The present invention is also directed to the novel compositions produced by such methods.

Tour, James M.↗

NASA NTRS1976

A far-ultraviolet photometer for planetary surface analysis

The measurement of local variations in the far-ultraviolet albedo is explored as a means of detecting changes in the refractive index of rocks and dust on the surface of atmosphereless planets and satellites. Far-ultraviolet spectrophotometric measurements of the lunar surface, which were obtained on the Apollo 17 orbital mission, are presented to demonstrate that significant albedo variations occur in the spectral range 120 to 170 nm. These data also confirm the hypothesis that the albedo variations represent refractive-index differences in the surface materials. A three-band photometer is described which, when put in orbit around a solar system object, is capable of providing refractive-index maps with a sensitivity of one part in the second decimal place and with kilometer resolution. Comparative surface-composition and surface-history analyses based on such maps are discussed.

Henry, R. C.↗

NASA NTRS1978

Surface temperatures and glassy state investigations in tribology, part 1

The research in this report is divided into two categories: (1) lubricant rheological behavior, and (2) thermal behavior of a simulated elastohydrodynamic contact. The studies of the lubricant rheological behavior consists of high pressure, low shear rate viscosity measurements, viscoelastic transition measurements, by volume dilatometry, dielectric transitions at atmospheric pressure and light scattering transitions. Lubricant shear stress-strain behavior in the amorphous glassy state was measured on several fluids. It appears clear from these investigations that many lubricants undergo viscoplastic transitions in typical EHD contacts and that the lubricant has a limiting maximum shear stress it can support which in turn will determine the traction in the contact except in cases of very low slide-roll ratio. Surface temperature measurements were made for a naphthenic mineral oil and a polyphenyl ether. The maximum surface temperature in these experiments was approximately symmetrical about the zero slide-roll ration except for absolute values of slide-roll ratio greater than about 0.9. Additional surface temperature measurements were made in contacts with rough surfaces where the composite surface roughness was approximately equal to the EHD film thickness. A regression analysis was done to obtain a predictive equation for surface temperatures as a function of pressure, sliding speed, and surface roughness. A correction factor for surface roughness effects to the typical flash temperature analysis was found.

Winer, W. O.↗

NASA NTRS1992

Remote sensing of Earth terrain

Research findings are summarized for projects dealing with the following: application of theoretical models to active and passive remote sensing of saline ice; radiative transfer theory for polarimetric remote sensing of pine forest; scattering of electromagnetic waves from a dense medium consisting of correlated Mie scatterers with size distribution and applications to dry snow; variance of phase fluctuations of waves propagating through a random medium; theoretical modeling for passive microwave remote sensing of earth terrain; polarimetric signatures of a canopy of dielectric cylinders based on first and second order vector radiative transfer theory; branching model for vegetation; polarimetric passive remote sensing of periodic surfaces; composite volume and surface scattering model; and radar image classification.

Kong, J. A.↗

NASA NTRS1993

Remote sensing of Earth terrain

Progress report on remote sensing of Earth terrain covering the period from Jan. to June 1993 is presented. Areas of research include: radiative transfer model for active and passive remote sensing of vegetation canopy; polarimetric thermal emission from rough ocean surfaces; polarimetric passive remote sensing of ocean wind vectors; polarimetric thermal emission from periodic water surfaces; layer model with tandom spheriodal scatterers for remote sensing of vegetation canopy; application of theoretical models to active and passive remote sensing of saline ice; radiative transfer theory for polarimetric remote sensing of pine forest; scattering of electromagnetic waves from a dense medium consisting of correlated mie scatterers with size distributions and applications to dry snow; variance of phase fluctuations of waves propagating through a random medium; polarimetric signatures of a canopy of dielectric cylinders based on first and second order vector radiative transfer theory; branching model for vegetation; polarimetric passive remote sensing of periodic surfaces; composite volume and surface scattering model; and radar image classification.

Kong, J. A.↗

NASA NTRS1994

(abstract) A Low-Cost Mission to 2060 Chiron Based on the Pluto Fast Flyby

The Pluto Fast Flyby-based mission to Chiron described in this paper is a low cost, scientifically rewarding, focused mission in the outer solar system. The proposed mission will make a flyby of 2060 Chiron, an active 'comet' with over 10(sup 4) times the mass of Halley, and an eccentric, Saturn-crossing orbit which ranges from 8.5 to 19 AU. This mission concept achieves the flyby 4.2 years after launch on a direct trajectory from Earth, is independent of Jupiter launch windows, and fits within Discovery cost guidelines. This mission offers the scientific opportunity to examine a class of object left unsampled by the trail-blazing Mariners, Pioneers, Voyagers, and missions to Halley. Spacecraft reconnaissance of Chiron addresses unique objectives relating to cometary science, other small bodies, the structure of quasi-bound atmospheres on modest-sized bodies, and the origin of primitive bodies and the giant planets. Owing to Chiron's large size (180<D<370 km), unique nature, and unusual orbit, this mission is likely to draw significant public interest. As described by COMPLEX, the SSEC, and later the SSES, flybys are the appropriate scale missions for initial reconnaissance missions. Carrying three sophisticated instruments, the proposed flyby will return critical data about Chiron's size, shape, polar obliquity, atmosphere, surface morphology, surface composition, internal structure, surface activity (including the nature of Chiron's outbursts), and origin. Engineering analysis indicates that the spacecraft is capable of navigating to and encountering Chiron at close approach distances of less than 5 000 km, well inside the 50 000 to 150 000 km coma, and perhaps within the collisional chemistry zone of the coma. The low cost of the proposed Chiron mission is based on the opportunity to use the planned Pluto Flyby spare spacecraft and a Proton Expendable Launch Vehicle (ELV) (the pluto spacecraft is being designed to be compatible with a Proton launch). Backup launch opportunities on Delta II and Atlas ELVs are available. The Pluto Fast Flyby mission plans to develop a low cost ($150M), lightweight (<150 kg) outer planet spacecraft which is well suited to flyby reconnaissance in the outer solar system. This Chiron flyby mission is designed to leverage SSED's Pluto spacecraft investment into a scientifically valuable successor mission within the Discovery cost cap. Taking advantage of the spare spacecraft, we estimate the Discovery Chiron intercept mission can be launched for less than $100 M. We believe this makes a highly attractive proposal, which maintains US presence and leadership in the study of the outer solar system, and enables the first-time exploration of a wholly new class of planetary target, an outer solar system planetesimal.

2060 Chiron planetesimal flyby Pluto Fast Flyby sp↗

NASA NTRS2007

Development and Evaluation of High Temperature Gaskets for Hypersonic and Reentry Applications

A wide variety of flexible gasket compositions were developed and tested at high temperatures. The gasket material system has high temperature capability. GRABER sealants were very effective in sealing machined ACC-4 composite surfaces. The gasket composition do not bond strongly with the ACC-4 substrate materials. The density of gasket materials can be tailored to show appropriate compressibility.

Singh, Mrityunjay↗

NASA NTRS2010

Exploiting the Free Landsat Archive for Operational Monitoring of Ecosystem Condition and Change Across the Chesapeake Bay Watershed

For the first time, all imagery acquired by the Landsat series of satellites is being made available by the USGS to users at no cost. This represents a key opportunity to use Landsat in a truly operational monitoring framework: large regions of the U.S. such as the Chesapeake Bay Watershed can now be analyzed using "wall-to-wall" imagery at timescales from approximately 1 month to several years. With the future launch of the Landsat Data Continuity Mission (LDCM) and Decadal Survey missions such as the hyperspectral HyspIRI, it is imperative to develop robust processing systems to perform annual ecosystem assessments over large regions such as the Chesapeake Bay. We have been working at NASA's Goddard Space Flight Center (GSFC) to develop an integrative framework for inserting 30m, annual, Landsat based data and derived products into the existing decision support system for the Bay, with a particular focus on ecosystem condition and changes over the entire watershed. The basic goal is to use a 'stack' of Landsat imagery with 40% or less cloud cover to produce multi-date (2005-2009 period), cloud/shadow/gap-free composited surface reflectance products that will support the creation of watershed scale land cover/ use products and the monitoring of ecosystem change across the Bay. Our scientific focus extends beyond the conventional definition of land cover (i.e. a classification of vegetation type) as we propose to monitor both changes in surface type (e.g. forest to urban), vegetation structure (e.g. forest disturbance due to logging or insect damage), as well as winter crop cover. These processes represent a continuum from large, interannual changes in land cover type, to subtler, intra-annual changes associated with short-term disturbance. The free Landsat data are being processed to surface reflectance and composited using the existing Landsat Ecosystem Disturbance Adaptive Processing System here at NASA/ GSFC, and land cover products (type, tree cover, impervious cover, winter cover) are being produced using well-established decision tree and regression tree algorithms. The goal of this session is to present the data products that we have been developing to the Bay science community and to discuss potential avenues for improvements and usage of the products for decision support.

BrowndeColstoun, Eric↗

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↗

NASA NTRS2005

Pickup Ion Mass Spectrometry for Surface Bounded Exospheres and Composition Mapping of Lunar and Planetary Surfaces

Many of the small to medium sized objects in the solar system can be characterized as having surface bounded exospheres, or atmospheres so tenuous that scale lengths for inter-particle collisions are much larger than the dimensions of the objects. The atmospheres of these objects are the product of their surfaces, both the surface composition and the interactions that occur on them and also their interiors when gases escape from there. Thus by studying surface bounded exospheres it is possible to develop insight into the composition and processes that are taking place on the surface and interiors of these objects. The Moon and Mercury are two examples of planetary bodies with surface bounded exospheres that have been studied through spectroscopic observations of sodium, potassium, and, on the moon, mass spectrometric measurements of lunar gases such as argon and helium.

Keller, J. W.↗