ALBERT

Description: This paper discusses some of the key options for Mars programs, missions, bases, elements, and systems. Program and mission options include Mars flyby, orbiting, and landing missions; they include near-term 'sortie' missions, and later, longer-duration Mars-base missions. Key program and mission parameters include the mix of manned/unmanned elements, the number and types of space vehicles used, types of science done, trajectory options and implications launch timing and schedules, etc. The key mission parameters strongly affect the nature, sizing, and quantity of earth-to-orbit (ETO) vehicles. On-orbit assembly of space vehicles (SVs) is also an important related consideration. The potential degree of utilization of the Space Station (SS) and other then-existing elements is a key question, and several possibilities are discussed in this paper. Several configurations of SVs are provided. Several options are identified for the Mars base infra-structure, and parametric data is shown for buildup of bases as a function of mission and vehicle type. Technologies required for the missions are also discussed.

Description: A substantial nightside ionosphere has been observed on Venus by both Mariner 5 and Mariner 10. Major dayside ionic species such as O2(+) and other molecular ions have chemical lifetimes much shorter than the 244.3-day rotation period of the planet. Rapid transport of ions from the dayside to the nightside to the extent required seems most unlikely. Consequently, possibilities are investigated for local production of ions on the nightside itself. Constraints imposed by chemical lifetimes require atomic ions with low ionization potentials. It is suggested that metallic ions of meteoric origin are the positive charge carriers, and the plausibility of this mechanism is demonstrated. Other possibilities are examined and shown to be less likely. Meteor ablation on Venus, the aeronomy of metallic species, and the role of negative ions near the electron peaks of the atmosphere are discussed.

Description: The Apollo 17 astronauts removed four rocks samples to represent each of the lithologies they recognized in the boulder at station 7: sample 77215 from an off-white meter-sized block; sample 77075 from one of the thin dikes that cross the off-white block; 77115 from the blue-gray rock adjacent to the off-white block and apparently continuous with thin dikes that cross the block; sample 77135 of the tan-gray or green-gray vesicular rock adjacent to the blue-gray (77115) rock. A consortium of investigators has been organized to study the samples. Each sample shows a number of lithologic types in terms of clasts (or xenoliths) and matrices. A table shows how subsamples have been allocated for consortium study. Maps and photographs show the relations between subsample locations and lithologies for the two more dissected samples, 77115 and 77135.

Description: Over nearly all of the surface of Venus the reflectivity and emissivity at centimeter wavelengths are about 0.15 and 0.85 respectively. These values are consistent with moderately dense soils and rock populations, but the mean reflectivity is about a factor of 2 greater than that for the Moon and other terrestrial planets. Pettingill and Ford, using Pioneer Venus reflectivities and emissivities, found a number of anomalous features on Venus that showed much higher reflectivities and much lower emissivities with both values approaching 0.5. These include Maxwell Montes, a number of high regions in Aphrodite Terra and Beta Regio, and several isolated mountain peaks. Most of the features are at altitudes above the mean radius by 2 to 3 km or more. However, such features have been found in the Magellan data at low altitudes and the anomalies do not exist on all high structures, Maat Mons being the most outstanding example. A number of papers have been written that attempt to explain the phenomena in terms of the geochemistry balance of weathering effects on likely surface minerals. The geochemists have shown that the fundamentally basaltic surface would be stable at the temperatures and pressures of the mean radius in the form of magnetite, but would evolve to pyrite and/or pyrrhotite in the presence of sulfur-bearing compounds such as SO2. Pyrite will be stable at altitudes above 4 or 5 km on Venus. Although the geochemical arguments are rather compelling, it is vitally important to rationally look at other explanations for radar and radio emission measurements such as that presented by Tryka and Muhleman. The radar reflectivity values are retrieved from the raw Magellan backscatter measurements by fitting the Hagfors' radar scattering model in which a surface roughness parameters and a normal incidence electrical reflectivity are estimated. The assumptions of the theory behind the model must be considered carefully before the results can be believed. These include that the surface roughness exists only at horizontal scales large compared to the wavelength, the vertical deviations are gaussianly distributed, there is no shadowing, and that the reflection occurs at the interface of two homogeneous dielectric half-spaces. Probably all these conditions are violated at the anomalous features under discussion. The most important of these is the homogeneity of the near surface of Venus, particularly in highlands. Under the assumptions of the theory, all of the radio energy is reflected by the impedance jump at the very boundary. However, in heterogeneous soil some fraction of the illuminating energy is propagated into the soil and then scattered back out by impedance discontinuities such as rock, voids, and cracks. In light soils, the latter effect can overwhelm the scattering effects of the true surface and greatly enhance the backscatter power, suggesting a much higher value of an effective dielectric constant that would be estimated from Hagfors' model.

Description: Solar wind induced magnetic fields may be present in the dayside ionosphere of Venus. A scale analysis and detailed calculations of the effects of different field line orientations on photoelectron transport and electron temperature show that horizontal magnetic fields considerably alter the profiles of electron heating and temperature and photoelectron flux. Direct injection of solar wind electrons has been considered, and the effects are minor. No evidence is found to support the suggestion that a sharp gradient in electron temperature is the cause of certain features in the Mariner-10 electron density profile.

Description: Major element chemical analyses often form the framework within which similarities and differences of analyzed specimens are noted and used to propose or devise models. When percentages are formed the ratios of pairs of components are preserved whereas many familiar statistical and geometrical descriptors are likely to exhibit major changes. This ratio preserving aspect forms the basis for a proposed framework. An analysis of compositional variability within the data set of 42 major element analyses of lunar reference samples was selected to investigate this proposal.

Description: The tetrataenite in Dayton was examined using conventional transmission (TEM) and analytical electron microscopy (AEM). Tetrataenite was also simulated in terrestrial Fe-Ni alloys through electron irradiation of thin-foil specimens on the high voltage electron microscope (HVEM). The purpose was to correlate the results of the TEM, AEM and HVEM studies on Dayton and on terrestrial iron-nickel alloys to the low temperature iron-nickel phase diagram. Oxide forms spontaneously on the surfaces of thin-foil iron-nickel specimens. By determining the metal/oxide orientation relationships the reflections due to the oxide and the superlattice are distinguished. In Dayaton, the clear taenite (I) is fully ordered until near the cloudy zone interface. The ordered domains ranged in size from 30 to 650 nm with the largest domains corresponding to the highest Ni content and the smallest domain size corresponding to the lowest Ni content. In terrestrial alloys irradiated on the HVEM, the extent of electron irradiation induced ordering was determined as a function of temperature and composition. Ordering occurred in every specimen irradiated.

Description: Optical, X-ray-diffraction and electron-microprobe techniques were used to investigate 0.26 gm of Apollo 14 soil sample 14259. Major element microprobe analyses were made of 470 mineral grains and 388 glass grains. The mineral abundances in the soil are 45% plagioclase, 41% pyroxene, 7% olivine, 3% oxides, 2% K-feldspar; 1% nickel-iron, and less than 1% troilite. The glasses have a wide range of compositions but preferred values are evident and are interpreted as representative of rock types contributing to the soil at the Fra Mauro site. Eleven per cent of the glasses have compositions like those of mare basalts or mare soils and are believed to be mare-derived. Eighty-six per cent of the glasses are equivalent in composition to basalts that have higher Al, and lower Ca/Al and Fe/Mg ratios than mare basalts. The most abundant compositional type is named Fra Mauro basaltic glass and is subdivided into three related types. The other major glass type in the soil corresponds in composition to anorthositic gabbro.

Description: Multispectral images of a lunar core segment are a new form of continuous data along the length of the core. A new laboratory arrangement was developed to obtain these images. Data processing and initial data analysis for core section 74002 were performed. The images are sensitive to variations in mineralogy and/or maturity of the soil and are easily used (1) in stratigraphic studies of the lunar regolith, (2) for sample selection of representative material, and (3) as ground truth for remote sensing studies.