Report of geophysics working group
Lunar exploration program to determine surface and interior physical properties of moon - heat flow measurements, seismology, traverse logging, and instruments for deep probes and surface use
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Lunar exploration program to determine surface and interior physical properties of moon - heat flow measurements, seismology, traverse logging, and instruments for deep probes and surface use
Photometry and polarimetry of the moon and their relationship to physical properties of lunar surface
An extensive investigation has been made of the characteristics of so-called "free return" trajectories. For the purposes of the study., these trajectories are defined as having certain symmetric properties which afford flight to the vicinity of the moon and return to earth without need for propulsion after the initial boost phase. The restricted three-body model for the earth-moon-probe system is used throughout. Two kinds of free return trajectories are shown to -exist and are studied. Of particular interest is the fact that for one kind of free return path, the largest inclination which can be achieved between the flight plane at periselenum and the plane of the moon's orbit about earth is about 10. 8 degrees while for the other kind of path the largest possible inclination is dependent on ·the radius at periselenum. In this case the inclination is limited to about 14 degrees or less for periselenum radius of 1938 km, but may be as great as 90 degrees with periselenum radius of 21150 km. Trajectories are also demonstrated which pass in front of the moon. These exhibit inclination behavior very much like that given by trajectories which go behind the moon. The injection velocity for these trajectories also changes only slightly from the circumlunar trajectories (less than 2 m/s for periselenum radius of 1938 km). However, the position of injection is changed considerably and the flight time may be increased by as much as five times that for circumlunar flight.
Optical properties of moon quantitatively compared with powder samples, bombarded with ions from hydrogen discharge plasma
Thermal properties of moon by comparing IR and microwave measurements of spectrum with theoretical calculation of upper layer temperature distribution
Quantitative data on photometric, luminescence, light polarization, color, infrared temperature, and microwave temperature properties of moon
The three major categories of models of lunar origin which explain the Moon's properties are complete and a more general scenario is presented. The model presented is as the Earth grew by planetesimal bombardment, a circumterrestrial cloud of particles was created from a combination of impact ejected mantle material and planetismals captured directly into orbit around the Earth. The compositional properties are explained two ways: (1) a few big late planetismals of diverse composition are captured in orbit and/or hit the Earth; and (2) the circumterrestrial swarm acts as a filter, preferentially capturing small weak silicate bodies, while passing large iron planetismals.
It is thought likely that extension of civilization beyond earth may include a permanent settlement on the moon. An analysis of the American civilian space program shows that the required technology for establishing a base on the moon will exist before the end of this century. A manned lunar base is discussed in terms of three distinct functions. The first is related to the scientific investigation of the moon and the application of special properties of the moon to research problems. In connection with the second, attention is given to the development of the capability to utilize the materials of the moon for beneficial purposes throughout the earth-moon system. The last involves research and development leading to a self-sufficient and self-supporting lunar base.
The physical properties of lunar rocks were measured using the vibrating bar technique in order to provide data for interpretation of geophysical results such as those from seismic measurements. The effect of volatiles on the mechanical Q in lunar rocks was studied in addition to the effect of exposing a sample to controlled amounts of those gases most likely to be present in the lunar environment or likely to have been outgassed from the lunar interior. The moderate temperatures to which the sample was exposed during the thermal treatment and the small drop in resonant frequency during the course of the outgassing suggests that there was little change in microfracture density. The frequency, composition and texture dependence of the damping were investigated, to study the loss mechanism.
A bibliography of articles entered into the data base at the Lunar and Planetary Institute Library from November 1982 through January 1983 is presented. An abstract of each article is given. The subjects covered by the articles include: the motion of the moon and dynamics of the earth-moon system: shape and gravity field of the moon; the physical structure of the moon, its thermal and stress history; the morphology of the lunar surface, the origin and stratigraphy of lunar formations, and mapping of the moon; the chemical composition of the moon, lunar petrology, mineralogy, and crystallography; electromagnetic properties of the moon; the planets; and other objects, including asteroids, comets, meteorites, and cosmic dust.
Understanding the properties of the uppermost lunar surface is critical as it is the optical surface that is probed by remote-sensing data, like that which is and will be generated by instruments on orbiting missions (e.g. M3, LRO). The uppermost material is also the surface with which future lunar astronauts and their equipment will be in direct contact, and thus understanding its properties will be important for dust mitigation and toxicology issues. Furthermore, exploring the properties of this uppermost surface may provide insight into conditions at this crucial interface, such as grain charging and levitation
Three objectives are stated for activities at a proposed manned lunar base. One objective is scientific investigation of the moon and its environment and the application of special properties of the moon to research problems. Another objective would be to produce the capability of using the materials of the moon for beneficial purposes throughout the earth-moon system. The third objective is to conduct research and development leading to a self-sufficient and self-supporting lunar base, the first extraterrestrial human colony. The potential benefits to earth deriving from these moon-based activities, such as technology development and realization, as well as growing industrialization of near-earth space, are addressed.
Theoretical tidal tilts and changes in gravitational acceleration make possible the determination of gross physical properties of the moon
Space weathering processes are known to be important on the Moon. These processes both create the lunar regolith and alter its optical properties. Like the Moon, Mercury has no atmosphere to protect it from the harsh space environment and therefore it is expected that it will also incur the effects of space weathering. However, there are many important differences between the environments of Mercury and the Moon. These environmental differences will almost certainly affect the weathering processes and the products of those processes. It should be possible to observe the effects of these differences in Vis (visible)/NIR (near infrared) spectra of the type expected to be returned by MESSENGER. More importantly, understanding these weathering processes and their consequences is essential for evaluating the spectral data returned from MESSENGER and other missions in order to determine the mineralogy and the Fe content of the Mercurian surface. Additional information is contained in the original extended abstract.
The physical properties, surface morphology, crater ejecta, and origin of Mars' moons Phobos and Deimos are considered in light of the intensive research done through the Mariner and Viking missions. Particular attention is given to orbits, secular acceleration and tides, photometric properties and phase curves, crater densities, grooves on Phobos, cratering mechanics, and dust belts.
The electromagnetic properties of the lunar interior are discussed with emphasis on (1) bulk, crustal, and local anomalous conductivity; (2) bulk magnetic permeability measurements, iron abundance estimates, and core size limits; (3) lunar ionosphere and atmosphere; and (4) crustal magnetic remanence: scale size measurements and constraints on remanence origin. Appendices treat the phase relationship between the energetic particle flux modulation and current disc penetrations in the Jovian magnetosphere (Pioneer 10 inbound) theories for the origin of lunar magnetism; electrical conductivity anomalies associated with circular lunar maria; electromagnetic properties of the Moon; Mare Serenitatis conductivity anomaly detected by Apollo 16 and Lunokhod 2 magnetometers; and lunar properties from magnetometer data: effects of data errors.
A method to enhance and detect subtle seismic arrivals typically used in terrestrial seismology, is to stack seismograms that have been time shifted to the predicted arrival time of a hypothetical phase of interest. We previously applied this array processing approach to the Apollo lunar seismic data, providing the first direct constraint on the size and state of the Moon's core. The method used travel time predictions made from pre-existing estimates of the crust and mantle velocities and densities and assumed that each of the Moons layers ia a uniform shell with no lateral variation or heterogeneity. In reality the structural properties of the Moon are likely inhomogeneous and vary both laterally and with depth.