摘要:

A review of Apollo 11, 12, and 14 and Luna 16 data shows that a genuine step‐function increase has occurred in our understanding of the moon. This results largely from the ability to conduct detailed analyses, most of which cannot be done by remote means, on returned sample. Geophysical data from Apollo‐emplaced science stations is a valuable complement to the new sample knowledge. It is evident that the great store of data previously gathered from earth‐based telescopic observations and unmanned spacecraft and the interpretations of it are enabling us to construct much better lunar models than otherwise possible. Without this pre‐existing framework, the lunar samples acquired would be of diminished value. The lunar ‘sum total experience’ will reach beyond the moon and should be particularly valuable in interpreting remotely sensed data from Mars and other planets.It appears that the moon originated about 4.6 b.y. ago, as did the earth and meteorites, thus at the beginning of the solar system. It seems to have suffered most of its internal thermal spasms in the first 1 or 2 b.y. of life and has been slowly dying since, in contrast to the earth, which today may be as active as ever. The lunar surface was exposed to a large but rapidly decreasing flux of infalling objects in its first 1½ b.y., some of which might have been part of the accretionary population that evidently formed the moon. That activity has been at a greatly diminished level for the past 3 b.y. and may now be comparable to the action of solar and galactic atomic particles in effecting surface modifications.The igneous processes that resulted in flooding of the mare basins with basaltic lavas are now reasonably well understood, as are the effects of meteoroids in generating the shallow (meter scale) surficial soil or regolith. Processes responsible for modification of the near‐surface layer (micron scale), which gives rise to the remotely sensed spectra, are not wholly clear. Evidence exists that the lunar near‐surface highlands are compositionally heterogeneous, but neither the mare basalts nor Imbrium ejecta (Fra Mauro) can be representative of the lunar deep‐interior composition. However, a good model of the ‘primordial’ or existing interior composition does not yet exist, although geochemical and geophysical evidence indicates that the deep interior may represent accreted material that has never been above the melting point. On the other hand, the outer regions have undergone severe chemical modification. These outer regions are, and probably always have been, depleted in volatile elements and enriched in refractories, an observation constraining models of lunar origin.All basic models of lunar origin (capture, dual‐planet, earth‐fission) are alive, although the idea of direct fission from earth is quite sick. Sicker yet, and essentially dead, are tektites‐ and meteorites‐from‐the‐moon hypotheses. The meteorite evidence does indicate, though, that processes similar to those forming lunar‐mare basalts occurred at other places in the early solar system.Questions relating to the origin of life must await future planetary exploration, for no life forms have been found, nor have organic molecules been unambiguously identified as being indigenous to the moon. The virtually complete lack of water and the 4+ b.y. of exposure to a harsh space environment make event

ISSN:8755-1209    

DOI:10.1029/RG009i003p00447

年代:1971

数据来源: WILEY

摘要:

Recognition of the magnitude and tectonic significance of oceanic volcanism has recently stimulated intensive investigation of the volcanic rocks and structures of the sea floor. An adequate interpretation of these features depends on a thorough understanding of submarine volcanic mechanisms. The pressure of deep water restricts the amount of vesiculation of eruptive magmas so that explosive activity is suppressed. Pillow lavas are probably shorter but thicker than subaerial flows of the same composition. Fragmental hyaloclastites are also important, but seem to be most common at relatively shallow depths. Most lavas and hyaloclastites are basaltic, but more siliceous pyroclastic deposits may be common in shallow seas of the continental shelves.Circumstantial evidence indicates that most abyssal basalts of the ocean floor were erupted at spreading centers and have been transported laterally. The rate of eruption of lavas is probably related to the mechanism of dike intrusion into a spreading center. Slow spreading rates result in less vertical transfer of heat, so that only relatively thick dikes reach the surface. Thinner dikes are chilled before erupting and cause a differential dilation of the crust that is reflected in shallow normal faulting. With increasing spreading rates, wall rocks are maintained at higher temperatures, and almost all dikes reach the surface to produce lava flows and smoother topography.Seamounts may begin to grow at ridge crests and continue as the volcano moves outward, but many must begin their activity far from the spreading center. Most of the submarine structure of seamounts must consist of pillow lavas with increasing amounts of hyaloclastites in the upper portion. Injection of dikes and sills adds substantially to the volume of the structure.Most abyssal basalts erupted at ridge crests are tholeiites, commonly with relatively high alumina contents. Silica‐deficient alkaline basalts become more common outward, especially at the crests of seamounts. The ultramafic rocks dredged from the mid‐Atlantic ridge fall into two classes. Some are clearly cumulate rocks related to associated gabbro and differentiated basalt. Others are strongly depleted in low‐melting components and appear to have been emplaced along fault zones; they may be derived from a residual layer from which basalt was extracted during an earlier episode of partial melting. It is difficult to find conclusive evidence that oceanic volcanism was as intense in pre‐Mesozoic time as it is postulated to b

ISSN:8755-1209    

DOI:10.1029/RG009i003p00523

年代:1971

数据来源: WILEY

摘要:

Tropospheric wave disturbances in the tropical western Pacific have been subjected to intensive analysis during three separate seasons. These all show evidence of spectral peaks in the 4‐ to 5‐day range and at periods longer than 10 days. In this review I attempt to synthesize the results for these three seasons, together with the analysis of a fourth season, into a tentative description of the various types of wave disturbances in this region. The conclusions are outlined below.It appears that there are two types of tropical disturbances that contribute to the 4‐ to 5‐day peaks: synoptic‐scale, westward‐propagating waves with phase speeds on the order of 6‐7 degrees per day, and planetary‐scale equatorial waves that extend into the lower stratosphere. There are also one or more wave types associated with the low‐frequency spectral peaks.All the tropical waves exhibit a similar vertical structure, with a phase reversal in the wind field between upper and lower troposphere. There are warm temperature anomalies at 300 mb, above the low‐level troughs, in qualitative agreement with the thermal‐wind equation. These warm anomalies coincide with the regions of maximum rising motion. As distinguished from tropical waves, the subtropical disturbances do not exhibit a phase reversal in the wind field between upper and lower tropospheric levels. The troughs of these waves appear to be colder than their surroundings at 300 mb.The available potential energy the tropical waves derive from condensation heating is immediately converted into kinetic energy by the synoptic‐scale divergent wind field. This appears to be the dominant energy source for these waves. The leakage of wave energy upward through the tropopause appears to be at least an order of magnitude smaller than the rate of energy generation.The spectral results indicate that most of the synoptic‐scale mass convergence into regions of disturbed weather takes place above the subcloud layer. Although the vertical distribution of latent heat release displays the same gross features in different regions, a simple linear proportionality between boundary‐layer convergence and condensation heating (as is usually assumed in the CISK hypothesi

ISSN:8755-1209    

DOI:10.1029/RG009i003p00557

年代:1971

数据来源: WILEY

摘要:

Clear‐air turbulence (CAT) presents a scientific problem of considerable importance to aviation and to attempts to understand atmospheric processes that must be incorporated in a long‐range numerical prediction model. Present knowledge about CAT is reviewed briefly, and the fact that the requirements of both aviation and atmospheric science for new information necessitate a measurement program whose objective is increased understanding of the physical mechanisms of CAT is emphasized. Specific investigations that should be a part of such a measurement program are presented, and the importance of the energy budget of CAT is stressed both for its scientific value and for its potential as a method of verifying accuracy of measured data. A new approach to determining the required accuracy of turbulence instrumentation, utilizing root‐mean‐square error techniques, is presented. Some aspects of the management of a large measurement program are also con

ISSN:8755-1209    

DOI:10.1029/RG009i003p00613

年代:1971

数据来源: WILEY

摘要:

We survey, in this paper, the properties of the zones of particle precipitation at high latitudes. We consider the average properties of particle influx from the outer magnetosphere as determined by satellite and rocket observations, as well as ground‐based techniques. The point of view of this paper is to try to associate source regions, and, if possible, precipitation mechanisms with each of the families of precipitating particles that collectively form the auroral zone. The precipitation patterns for both electrons and protons exhibit a diurnal variation. The several zones of particle precipitation can be placed in relationship to each other. The zone of electron precipitation is best described as consisting of a region at low latitudes (60° ⪝ Λ ⪝ 70° near local midnight) where electrons with characteristic energies of tens of kev precipitate; this region merges and overlaps at the higher latitudes with another region (70° ⪝ Λ ⪝ 80° near local midnight) characterized by precipitating electrons of ≈0.5 kev. The limited data available indicate that the zone of proton precipitation spatially overlaps the zone of electron precipitation. For example, the peak of precipitation of>4‐kev protons near local midnight is found between Λ = 65° and Λ = 70°. Near local noon a separate region of very soft proton precipitation is found in the vicinity of Λ ≈ 80°, in addition to a region of proton influx at lower latitudes. We consider the plasma sheet, the extraterrestrial ring current, the polar cusp, and the outer radiation belt as source regions of precipitating particles. Brief surveys of the precipitation of helium ions and of possible means of artificially inducing particle prec

ISSN:8755-1209    

DOI:10.1029/RG009i003p00659

年代:1971

数据来源: WILEY

摘要:

An introductory review of theories of plasma instabilities in the magnetosphere is presented. PartAis a review of theories of plasma instabilities that are relevant to magnetospheric plasmas. Instabilities arising from velocity‐distribution anisotropies, such as a pitch‐angle anisotropy or the presence of beams, as well as instabilities from nonuniform distributions of plasmas and magnetic fields, are discussed. Particular emphasis is placed on the effect of a mixture of a cold plasma in a high‐β plasma. PartBis a summary of works related to actual plasma instabilities in the magnetosphere. In view of the observed plasma parameters, it is shown that the magnetosphere is rather stable against most macroscopic instabilities, and its dynamics are predominantly governed by microscopic instabi

ISSN:8755-1209    

DOI:10.1029/RG009i003p00703

年代:1971

数据来源: WILEY

摘要:

Our knowledge of the large‐scale properties of the interplanetary magnetic field is reviewed. The early theoretical work of Parker is presented, along with the observational evidence supporting his Archimedes spiral model. The variations present in the interplanetary magnetic field from the spiral angle are related to structures in the solar wind. The causes of these structures are found to be either nonuniform radial solar wind flow or the time evolution of the photospheric field. The coronal magnetic models are related to the connection between the solar magnetic field and the interplanetary magnetic field. The direct extension of solar field‐magnetic nozzle controversy is discussed, along with the coronal magnetic models. The effect of active regions on the interplanetary magnetic field is discussed with particular reference to the evolution of interplanetary sectors. The variation of the interplanetary magnetic field magnitude is shown throughout the solar cycle. The percentage of time the field magnitude is greater than 10 γ is shown to closely parallel sunspot number. The suggested influence of the sun's polar field on the interplanetary field and alternative views of the magnetic field structure out of the ecliptic plane are presented. In addition, a variety of significantly different interplanetary field structures are discu

ISSN:8755-1209    

DOI:10.1029/RG009i003p00773

年代:1971

数据来源: WILEY

摘要:

A rarified atmosphere should be present on the moon because of contributions from the solar wind, meteoric volatilization, and internal degassing. Transient contributions to the atmosphere must be produced by rocket gases during lunar missions. These gases may obscure the ambient atmosphere in the vicinity of the landing site for a period of several months after a lunar landing. Of the three natural sources, definite predictions can be made only on the basis of solar wind input. The lunar atmosphere of solar origin is expected to consist mainly of neon, lighter gases being less prevalent because of their more rapid thermal escape and leaves gases less prevalent because of their lesser concentrations in the solar wind. Daytime néon concentrations are expected to be near 6 × 104cm−3, and nighttime concentrations are expected to be near 1.5 × 106

ISSN:8755-1209    

DOI:10.1029/RG009i003p00813

年代:1971

数据来源: WILEY

摘要:

Current problems and developments in the theory of the large‐scale expansion of the solar corona are reviewed. The outstanding question is whether the energy supply to the quiet corona is mainly thermal conduction outward from a region of active heating at its base or mainly wage propagation outward from the base. It is suggested that the question can be settled only when the properties of the wind can be sampled over a wide range of radial distance from the sun, from far inside the orbit of earth to well beyond. It has been suggested that hydromagnetic waves may drive the expansion of the active corona by direct transfer of momentum as well as energ

ISSN:8755-1209    

DOI:10.1029/RG009i003p00825

年代:1971

数据来源: WILEY

ISSN:8755-1209    

DOI:10.1029/RG009i003p00837

年代:1971

数据来源: WILEY