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The American and Russian 1978 Venus explorations are reported. Highlights of their accomplishments and subjects of study are discussed. Included are investigations of the surface pressure, temperature, composition, and mass of the Venusian atmosphere, along with cloud layer structure, greenhouse effect, and diurnal variations.
The paper presents a summary of new knowledge about Mars obtained from Mariner and Viking missions. Specific subjects include Martian geologic features, composition of the surface, the atmosphere, and the polar caps, and Martian meteorology, including temperatures, pressures, tides, dust storms, and atmospheric water vapor. The program of further Mars exploration is outlined. The major element of the program will be a sample return mission, utilizing orbiters and limited-range rovers with enough instrumentation to identify, acquire, and return well documented samples from two or more sites.
Mission requirements of the derivative design were the same as the baseline to readily identify the advanced technology benefits achieved. Advanced technologies investigated were in the areas of propulsion, structures and aerodynamics and a direct operating cost benefit analysis conducted to identify the most promising. Engine improvements appear most promising and combined with propeller, airfoil, surface coating and composite advanced technologies give a 21-25 percent DOC savings. A 17 percent higher acquisition cost is offset by a 34 percent savings in fuel used.
The principal scientific results from the Apollo Program are reviewed. Data on the nature of the moon, including the surface, interior, and composition, are discussed. Attention is also given to problems of lunar age determination, and to certain unanswered questions concerning the moon (e.g., the chemical composition of the whole moon and the moon's asymmetry). A number of illustrative photographs are presented.
The general characteristics of the Galilean satellites, as determined from Voyager data, are described. Attention is then given to the characteristics (surface features, colors, compositions, and geophysical and geochemical processes) of the particular satellites. Particular consideration is given to the nature of Io's atmosphere and to magnetospheric interactions.
Methods for remote sensing of elemental composition of the surfaces of planets, comets, and asteroids are considered. The abundance of certain elements with different condensation temperatures and with various types of geochemical behavior provide data relative to the origin and evolution of these bodies. Solar X-ray fluorescence, and primary and secondary galactic cosmic ray interactions are highlighted as the major remote sensing methods.
Topics discussed include basaltic studies, planetary differentiation (e.g., lunar highland rocks), and remote sensing studies of chemical composition, mineralogic composition, and physical surface properties. Particular attention is given to the petrology and chemistry of basaltic fragments from the Apollo 11 soil; a model of early lunar differentiation; rocks of the early lunar crust; refractory and moderately volatile element abundances in the earth, moon, and meteorites; the effects of overlapping optical absorption bands of pyroxene and glass on the reflectance spectra of lunar soils; and the characterization of Martian surface materials from earth-based radar.
The total geoid anomaly which is the result of a given density contrast in a convecting viscous earth is affected by the mass anomalies associated with the flow induced deformation of the upper surface and internal compositional boundaries, as well as by the density contrast itself is discussed. If the internal density contrasts can be estimated, the depth and variation of viscosity with depth of the convecting system can be constrained. The observed long wavelength geoid is highly correlated with that predicted by a density model for seismically active subducted slabs. The amplitude of the correlation is explained if the density contrasts associated with subduction extend into the lower mantle or if subducted slabs exceeding 350 km in thickness are piled up over horizontal distances of thousands of km at the base of the upper mantle. Mantle wide convection in a mantle that has a viscosity increasing with depth provides the explanation of the long-wavelength geoid anomalies over subduction zones.
Electromagnetic radiation is emitted by matter which was heated to a temperature above absolute zero. The amount of blackbody radiation in the microwave frequency region of interest (10 to the 8th power f 10 to the 10th power Hz) emitted by matter can be determined from the Rayleigh-Jeans approximation to Planck's Radiation Law. The amount of electromagnetic radiation from matter which is not a blackbody is a function of the emissivity of the material. The emissivity is a factor less than unity and is a function of several parameters including chemical composition, temperature, frequency, surface characteristics, and viewing angle. A radiometer is an instrument which detects and provides a measure of the electromagnetic radiation being emitted by a material or surface area within the radiometer's antenna beamwidth. Microwave radiometers provide the capability for remote measurements from Earth orbits of geophysical parameters. These measurements will require the use of a microwave imaging radiometer using a large aperture deployable antenna with multiple beams in a pushbroom mode to achieve high spatial resolution and large swath width.
The goal of the study described here is to determine new criteria for improved target discrimination in areas of hydrothermal mineralization. It is noted that the portion of materials, that is, geological surfaces detected by sensing devices, must be accurately determined before elemental and mineralogical characterization. The depth from which visible-near infrared radiation is reflected from target surfaces depends on composition and fabric. Reflectance spectra are obtained from binary mixtures of hematite, goethite, kaolinite and montmorillonite with a reflecting sphere spectrometer over a wavelength range of 400-2500 nm. The reflection (or absorption) intensity is plotted vs. the sample thickness (determined by scanning electron microscopy) to determine the sample thickness at which absorption saturates. The optical depth is seen to vary as a function of mineralogy and wavelength. In general, the maximum depth from which reflection features are discerned is from 12 to 47 microns measured in the visible-near infrared spectral region.
A relatively simple, yet accurate, relationship between the microwave brightness temperature of the ocean and conventional oceanographic and meteorological parameters is derived. The equation for the brightness temperature upwelling from the sea surface through the intervening atmosphere is obtained, considering radiative emission and scattering by the sea surface along with radiative absorption and emission by the atmosphere. A number of approximations are applied to the integral brightness temperature equation and its supporting equations in order to obtain a simple equation for the brightness temperature that does not contain integrals. Values for a number of atmospheric parameters are determined, including temperature sensitivities, oxygen opacity, water vapor and liquid water normalized absorption coefficients, and effective columnar height. The sea surface emissivity model is then considered, modelling the sea surface as a composite of foam-free rough water and foam patches.
The interaction of a two dimensional sonic jet injected transversely into a confined main flow was studied. The main flow consisted of air at a Mach number of 2.9. The effects of varying the jet parameters on the flow field were examined using surface pressure and composition data. Also, the downstream flow field was examined using static pressure, pitot pressure, and composition profile data. The jet parameters varied were gapwidth, jet static pressure, and injectant species of either helium or nitrogen. The values of the jet parameters used were 0.039, 0.056, and 0.109 cm for the gapwidth and 5, 10, and 20 for the jet to mainstream static pressure ratios. The features of the flow field produced by the mixing and interaction of the jet with the mainstream were related to the jet momentum. The data were used to demonstrate the validity of an existing two dimensional elliptic flow code.
The total geoid anomaly which is the result of a given density contrast in a convecting viscous earth is affected by the mass anomalies associated with the flow induced deformation of the upper surface and internal compositional boundaries, as well as by the density contrast itself is discussed. If the internal density contrasts can be estimated, the depth and variation of viscosity with depth of the convecting system can be constrained. The observed long wavelength geoid is highly correlated with that predicted by a density model for seismically active subducted slabs. The amplitude of the correlation is explained if the density contrasts associated with subduction extend into the lower mantle or if subducted slabs exceeding 350 km in thickness are piled up over horizontal distances of thousands of km at the base of the upper mantle. Mantle wide convection in a mantle that has a viscosity increasing with depth provides the explanation of the long-wavelength geoid anomalies over subduction zones. Previously announced in STAR as N83-22874
It is pointed out that environment-assisted subcritical crack growth in high-strength steels and other high-strength alloys (particularly in hydrogen and in hydrogenous environments) is an important technological problem of long standing. This problem is directly related to issues of structural integrity, durability, and reliability. The terms 'hydrogen embrittlement' and 'stress corrosion cracking' have been employed to describe the considered phenomenon. This paper provides a summary of contributions made during the past ten years toward the understanding of environmentally assisted crack growth. The processes involved in crack growth are examined, and details regarding crack growth and chemical reactions are discussed, taking into account crack growth in steels exposed to water/water vapor, the effect of hydrogen, reactions involving hydrogen sulfide, and aspects of fracture surface morphology and composition. Attention is also given to the modeling of crack growth response, crack growth in gas mixtures, and the interaction of solute atoms with the crack-tip stress field.
The VESTA project, a Franco-Soviet collaboration, is described. The VESTA probe will be launched and will pass through the asteroid belts before encountering comets. The probe will be an autonomous vehicle. The scientific objectives are to obtaining information on asteroids, comets, solar system formation, meteorites and other sources of extraterrestrial material. The surface morphology, mineral composition and internal structure of asteroids will be studied.
A systems approach was adopted to study the pocketing phenomena on a solid rocket nozzle liner. The classical thermoelastic analysis was used to identify marginally strained regions on the composite liner erosion surface and at a depth coincident with the peak value of the across ply coefficient of thermal expansion. A failure criterion was introduced which included a thermal term and permitted failure assessment over the charred liner. The method was verified by satisfactory application to a reported related experiment. Liner pocketing mechanism was attributed to very localized material degradation caused during manufacturing process either by reduction of fiber strength and/or by concentration of resin volume fraction. Pocketing scenario over the degraged material was constructed with supporting formulation to predict size of fissures with respect to degraded material size and location in the liner and with burn time. Sensitivities of liner material parameters were determined to influence test programs designed to update mechanical data base of carbon cloth phenolic over the char temperature range.
Four tables of planetary and satellite data are presented which list satellite discoveries, planetary parameters, satellite orbits, and satellite physical properties respectively. A scheme for classifying the satellites is provided and it is noted that most known moons fall into three general classes: regular satellites, collisional shards, and irregular satellites. Satellite processes are outlined with attention given to origins, dynamical and thermal evolution, surface processes, and composition and cratering. Background material is provided for each family of satellites.
Green glass from Apollo 15 lunar clod 15426 (collected from the north rim of Spur Crater), known to be the most primitive among sampled lunar volcanic rocks, was analyzed for Pb isotopic compositions and concentrations of U, Th, and Pb. Hand-picked green glass and yellow impact glass particles were washed with water and a mixture of HBr and HF, and the washes and residues, spiked with a mixure of U-233-U-236-Th-230-Pb-205, were subjected to U-Th-Pb analyses. In contrast to the case of the Apollo 17 orange glass, the isotopic composition of lead from the surfaces of the green glass spherules is totally different from that of the spherules' interiors but is similar to the composition of lunar surface lead. Data for the interior lead yield a Pb-207/Pb-206 age of 3.41 Ga. The data indicate that lunar Pb evolved in an environment with U-238/Pb-204 ratios of 19 to 55, which is considerably lower than those for mare basalts (about 300) but higher than the earth values (6-8).