Lunar surface strength: implications of luna 9 landing

The ability of the lunar surface to support statically the Luna 9 copsule indicates that the surface can bear at least 5 x 10(3) dyne per square centimeter (10(-1) lb/in.(2)). Analysis of the landing dynamics, using available data, gives a lower bound of about 1 to 2 x 10(5) dyne/cm(2), but this estimate may not be conservative because of uncertainties regarding the shock-absorbing system used and the direction of the velocity vector at impact.     

Lunar surface: identification of the dark mantling material in the apollo 17 soil samples

Evidence indicates that Apollo 17 sample 74001, a soil consisting of very dark spheres, is composed almost entirely of the dark mantling material that covers a large region of the southeastern boundary of Mare Serenitatis. Other Apollo 17 samples contain only a component of this material. The underlying basalt in the Taurus-Littrow valley appears to be an extension of material forming the low-albedo ring around part of Mare Serenitatis and much of the surface of Mare Tranquillitatis. The surface of this basalt region is spectrally distinct from areas with dark mantling material. These results are derived fromn telescopic and laboratory measurements of the optical properties of lunar soil. Digital vidicon color images are used to map the extent of these material units in the Taurus-Littrow region.     

Lunar topography: first radar-interferometer measurements of the alphonsus-ptolemaeus-arzachel region

Radar interferometry is a new technique for accurately measuring the topography of the lunar surface from the earth. Measurements have been made with this technique of an area including the craters Ptolemaeus, Alphonsus, and Arzachel and a portion of Mare Nubium. There is evidence for a late episode of volcanism that partially filled two of the craters through a crustal fault of Imbrian origin. Several other features of the topography, particularly those coinciding with local gravitational anomalies, can be correlated with flow events.     

Lunar apennine-hadley region: geological inplications of Earth-based radar and infrared measurements

Recently completed high-resolution radar maps of the moon contain information on the decimeter-scale structure of the surface. When this information is combined with eclipse thermal-enhancement data and with high-resolution Lunar Orbiter photography, the surface morphology is revealed in some detail. A geological history for certain features and subareas can be developed, which provides one possible framework for the interpretation of the findings from the Apollo 15 landing. Frequency of decimeter-and meter-size blocks in and around lunar craters, given by the remote-sensed data, supports a multilayer structure in the Palus Putredinis mare region, as well as a great age for the bordering Apennine Mountains scarp.     

Lunar surface chemistry: a new imaging technique

Detailed chemical maps of the lunar surface have been constructed by applying a new weighted-filter imaging technique to Apollo 15 and Apollo 16 x-ray fluorescence data. The data quality improvement is amply demonstrated by (i) modes in the frequency distribution, representing highland and mare soil suites, which are not evident before data filtering and (ii) numerous examples of chemical variations which are correlated with small-scale (about 15 kilometer) lunar topographic features.     

Lunar surface: composition inferred from optical properties

The optical characteristics (intensity, polarization, spectrum, and albedo) of the moon surface are compared with those of rock and meteorite powders. The only materials whose optical properties match those of the lunar surface are basic rocks containing lattice iron but little or no free iron, and then only after irradiation of these rocks by a simulated solar wind. Optical properties of chondritic meteorite powders differ from those of the moon in significant respects. The lunar crust is probably not chondritic, but is similar in composition to terrestrial iron-rich basalts. These results are independent of those from the Surveyor V alpha-scattering experiment and, in addition, provide a basis for extrapolating the Surveyor V analysis to other areas of the moon. The Surveyor V experiment has thus confirmed the value of earth-based optical techniques for the study of the structure and composition of the surfaces of other planets.     

Lunar surface: changes in 31 months and micrometeoroid flux

Comparison of pictures of the lunar surface taken 31 months apart by Surveyor 3 and Apollo 12 show only one change in the areas disturbed by Surveyor: a 2-millimeter particle, in a footpad imprint, that may have fallen in from the rim or been kicked in by an approaching astronaut. Vertical walls 6 centimeters high did not collapse and dark ejecta remained dark. No meteorite craters as large as 1.5 millimeters in diameter were seen on a smooth soil surface 20 centimeters in diameter; this indicates a micrometeoroid flux lower than 4 x 10(-7) micrometeoroids per square meter-second at an energy equivalent to about 3 x 10(-8) gram at 20 kilometers per second. This flux is near the lower limit of previous determinations.     

Lunar magnetic anomalies and surface optical properties

For typical solar wind conditions, lunar magnetic anomalies with dipole moments m > 5 x 10(13) gauss-cubic centimeters will strongly deflect the solar wind, producing local plasma voids at the lunar surface. The correlation of the largest observed anomalies (m approximately 10(16) gauss-cubic centimeters) with unusual, relatively high albedo surface features may therefore imply that solar wind ion bombardment is an important determinant of the optical properties of the lunar surface.     

Lunar experiments: the moon as a site for certain physical measurements

If the lunar surface becomes available for conducting physical experiments, it may be particularly suited to thermal neutron and molecular and atomic beam measurements. The application of these beams for the purpose of communication on the lunar surface appears possible.     

Bone density measurements in vivo: improvement of x-ray densitometry

An X-ray bone densitometer has been developed which makes direct tracings of absorption curves on a nearly linear scale. Speed and precision are increased by elimination of x-ray film. Results are reproducible to within 3 percent with a phantom finger, and within 6 percent with human subjects.     

Lunar surface radioactivity: preliminary results of the apollo 15 and apollo 16 gamma-ray spectrometer experiments

Gamma-ray spectrometers on the Apollo 15 and Apollo 16 missions have been used to map the moon's radioactivity over 20 percent of its surface. The highest levels of natural radioactivity are found in Mare Imbrium and Oceanus Procellarum with contrastingly lower enhancements in the eastern maria. The ratio of potassium to uranium is higher on the far side than on the near side, although it is everywhere lower than commonly found on the earth.     

A material with electrically tunable strength and flow stress

The selection of a structural material requires a compromise between strength and ductility. The material properties will then be set by the choice of alloy composition and microstructure during synthesis and processing, although the requirements may change during service life. Materials design strategies that allow for a recoverable tuning of the mechanical properties would thus be desirable, either in response to external control signals or in the form of a spontaneous adaptation, for instance in self-healing. We have designed a material that has a hybrid nanostructure consisting of a strong metal backbone that is interpenetrated by an electrolyte as the second component. By polarizing the internal interface via an applied electric potential, we accomplish fast and repeatable tuning of yield strength, flow stress, and ductility. The concept allows the user to select, for instance, a soft and ductile state for processing and a high-strength state for service as a structural material.     

Lunar surface magnetic fields and their interaction with the solar wind: results from lunar prospector

The magnetometer and electron reflectometer experiment on the Lunar Prospector spacecraft has obtained maps of lunar crustal magnetic fields and observed the interaction between the solar wind and regions of strong crustal magnetic fields at high selenographic latitude (30 degreesS to 80 degreesS) and low ( approximately 100 kilometers) altitude. Electron reflection maps of the regions antipodal to the Imbrium and Serenitatis impact basins, extending to 80 degreesS latitude, show that crustal magnetic fields fill most of the antipodal zones of those basins. This finding provides further evidence for the hypothesis that basin-forming impacts result in magnetization of the lunar crust at their antipodes. The crustal magnetic fields of the Imbrium antipode region are strong enough to deflect the solar wind and form a miniature (100 to several hundred kilometers across) magnetosphere, magnetosheath, and bow shock system.     

Lunar atmosphere as a source of argon-40 and other lunar surface elements

The lunar atmosphere is the likely source of excess argon-40 in lunar surface material; about 8.5 percent of the argon-40 released into the lunar atmosphere will be implanted in the surface material by photoionization and subsequent interaction with fields in the solar wind. The atmosphere is also likely to be the source of other unexpected surface elements or of solar wind elements that impact from non-solar wind directions.     

Lunar maria: structure and evolution

The lunar maria are considered to have evolved as homologous, transient, gravity-wave systems from large impact craters on a crustal layer 50 kilometers thick, fluidized from beneath by prompt, shock-induced melting inside an initially hot moon.     

Lunar crust: structure and composition

Lunar seismic data from artificial impacts recorded at three Apollo seismometers are interpreted to determine the structure of the moon's interior to a depth of about 100 kilomneters. In the Fra Mauro region of Oceanus Procellarum, the moon has a layered crust 65 kilometers thick. The seismic velocities in the upper 25 kilometers are consistent with those in lunar basalts. Between 25 and 65 kilometers, the nearly constant velocity (6.8 kilometers per second) corresponds to velocities in gabbroic and anorthositic rocks. The apparent velocity is high (about 9 kilometers per second) in the lunar mantle immediately below the crust.     

Elemental composition of lunar surface material

Elemental abundances, so far obtained, derived from the analysis of Apollo 11 lunar material are reported. Similarities and differences exist between lunar material, the eucritic achondrites, and the augite achondrite Angra dos Reis, the analysis of which is also reported.     

Venus: density of upper atmosphere from measurements of drag on pioneer orbiter

Measurements of the changes in orbital period of the Pioneer Venus orbiter have yielded estimates of the density of the upper atmosphere of Venus at altitudes in the range from 150 to 200 kilometers. At the lower limit of this range, the density on the dayside of the terminator exhibits a temporal variation of amplitude near 4 x 10(-14) gram per cubic centimeter aboult a mean of approximately 1.4 x 10(-13) gram per cubic centimeter. The variation appears oscillatory, with a 4- to 5-day period, but barely one cycle was observed. The density on the nightside of the terminator, sampled inthe same 150-kilometer altitude range, fluctuates about a smaller mean of approximately 4 x 10(-14) gram per cubic centimeter. The density between the altitudes of 150 and 200 kilometers, sampled only on the dayside of the terminator, imply a scale height of between 15 and 20 kilometers. The interpretation of this estimate is uncertain, however, in view of the measurements at the different altitudes having been made at different times and, hence, at different values of solar phase.