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At least 1,333 records · Page 74
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Geophysical parameters of the earth-moon system

Doppler tracking data from Lunar Orbiter 4 have been combined with laser ranging data from lunar retroreflectors to yield a number of geophysical and geodetic parameters for the earth and moon. This joint solution gives values of (1) the lunar principal polar moment C/M R squared = 0.3905 plus or minus 0.0023, (2) GM(E) = 398600.461 plus or minus 0.026 cu km/sq s, and (3) an earth/moon mass ratio at 81.300587 plus or minus 0.000049. Also determined are the harmonics of a complete lunar gravity field through degree and order 5, the obliquity of the lunar pole, selenocentric coordinates of the lunar retroreflectors, geocentric coordinates of the McDonald Observatory, and the lunar secular acceleration. The lunar potential Love number is weakly determined at 0.022 plus or minus 0.013, and a suprisingly large dissipation of rotational energy is inferred, though either solid body tidal dissipation or liquid core mantle interactions could be causes.

Ferrari, A. J.↗
NASA NTRS1980

Doubly-periodic orbits in the Sun-Earth-Moon system

A series of periodic orbits in the Earth-Moon circular restricted problem of three bodies was found which is ideally suited for exploring the Earth's geomagnetic tail. The mean apsidal motion of the basic highly elliptical Earth orbit was maintained at about one degree per day by a sequence of lunar swingbys, keeping the apogees in the anti-Sun direction. The orbits were periodic in reference frames rotating at both lunar and solar rates. Apogee distances were alternately raised and lowered by the lunar swingby maneuvers. Several categories of these Sun-synchronous double lunar swingby orbits were identified. The strength and flexibility of this trajectory concept was demonstrated with real world simulations.

Farohar, R.↗
NASA NTRS1980

Moon and earth - Compositional differences inferred from siderophiles, volatiles, and alkalis in basalts

A comparison of RNAA analyses of 18 trace elements in 25 low-Ti lunar and 10 terrestrial oceanic basalts indicated that the volatiles such as Ag, Bi, and Br are depleted in lunar basalts by nearly constant factors of 0.026 relative to terrestrial basalts. This constancy is not consistent with models that derive the moon's volatiles from partial recondensation of the earth's mantle or from partial degassing of a captured body; it is consistent with models which derive planetary volatiles from a thin veneer of C-chondrite material. Chalcogens (Se and Te) have almost constant and identical abundances in lunar and terrestrial basalts; siderophiles show abundant Ni in lunar basalts, while Ir, Re, Ge, and Au are depleted.

Wolf, R.↗
NASA NTRS1980

Geochemical anomalies on the eastern limb and farside of the moon

A variety of orbital geochemistry and photogeologic data was used to investigate major geochemical anomalies on the east limb and farside of the moon and to determine the processes responsible for their formation. These anomalies are located in the following regions: (1) near Langemak crater, (2) Mare Marginis, (3) Balmer crater, (4) terrain north of Taruntius crater, and (5) Van de Graaff. It was concluded that these anomalies are related to episodes of extrusive igneous activity which produced deposits with a variety of ages and compositions. Some of the associated volcanic deposits exhibit albedos and surface morphologies similar to those of the nearside maria, while others are now thinly covered by highland debris and are commonly represented by light plains units which exhibit clusters of dark-haloed craters. Little evidence was found for a genuine episode of highland volcanism (e.g., Apollo 15 KREEP basalt, highland basalt, etc.). The existence of intermediate basalts on the eastern limb and farside supports previous suggestions that KREEP-like volcanism was not limited to a small area of the lunar nearside. Eastern limb and farside volcanic activity has been more extensive in both space and time and has produced a greater variety of compositions than has previously been thought. Since thinly covered basaltic units can exert a strong influence on regional surface chemistry as determined from orbit, caution is urged in interpreting the surface compositions of highland terrains which exhibit a high density of dark-haloed impact craters.

Hawke, B. R.↗
NASA NTRS1981

Tidal dissipation in the moon

Euler's equations of motion, modified to include elasticity and solid friction, were used to study the rotation of the moon. Two heuristic models for the anelasticity were considered: Q independent of frequency and Q inversely proportional to the frequency and Q inversely proportional to the frequency of the strain oscillation. Parameters in each model were estimated by weighted least squares from 9 years of lunar laser range observations. The root mean square of the postfit range residuals was 19 cm in each case. For a strain period of 1 month, the estimates of Q obtained with the two models were similar and surprisingly low: 23 + or - 6. The range of uncertaintly, + or - 6, represents our estimate of the true standard deviation of the estimate of Q, as affected by systematic errors; it is 3 times larger than the formal, statistical, standard error.

Cappallo, R. J.↗
NASA NTRS1981

Eruption mechanics on the earth, moon and Mars

A survey is provided of recent comparative studies on the character of eruption mechanics on earth, the moon and Mars. Among the relevant determinations made are: (1) a source depth for lunar basaltic magmas deeper, at 100 km, than most terrestrial ones; (2) the rising of both lunar and terrestrial magmas to less than 2 km below the surface before gases begin to exsolve; (3) carbon monoxide concentrations in lunar basalts are an order of magnitude lower than the average volatile contents of terrestrial basalts; and (4) unequivocal proof is lacking for the existence of ignimbrites in Martian volcanic formations, which would be formed by the collapse of large eruption columns.

Wadge, G.↗
NASA NTRS1980

The ancient sun: Fossil record in the earth, moon and meteorites; Proceedings of the Conference, Boulder, CO, October 16-19, 1979

Papers are presented concerning theories of solar variability and their consequences for luminosity, particle emission and magnetic field changes within the past 4.5 billion years, and on the records of such solar behavior in lunar, meteoritic and terrestrial materials. Specific topics include the neutrino luminosity of the sun, the relation of sunspots to the terrestrial climate of the past 100 years, solar modulation of galactic cosmic rays, the historical record of solar activity, C-14 variations in terrestrial and marine reservoirs, and solar particle fluxes as indicated by track, thermoluminescence and solar wind measurements in lunar rocks. Attention is also given to the spin-down of the solar interior through circulation currents and fluid instabilities, grain surface exposure models in planetary regoliths, rare gases in the solar wind, nitrogen isotopic variations in the lunar regolith, the influence of solar UV radiation on climate, and the pre-main sequence evolution of the sun and evidence of the primordial solar wind in the electromagnetic induction heating of the asteroids and moon.

Pepin, R. O.↗
NASA NTRS1980

Electromagnetic inductive heating of the asteroids and moon as evidence bearing on the primordial solar wind

Thermal evolutionary models of the asteroids and the moon based on the hypothesis of electrical inductive heating by a dense primordial solar wind are compared with observation. Inferences (derived from spectroscopy) of asteroidal mineralogy when compared with electrical heating models, the variation of cooling rates recorded in iron meteorites, and the occurrence of the lunar magma ocean event lend support to the hypothesis of inductive heating. A high primordial solar rotation rate and magnetic field together with the loss due to plasma outflow of a substantial fraction of the initial solar mass would follow.

Herbert, F.↗
NASA NTRS1981

Moon - Near-infrared spectral reflectance, a first good look

Spectral reflectance contains direct information on the mineralogy of the surface soils and rocks. A problem concerning the employment of remote spectral-reflectance sensing techniques for mineralogical studies is related to the lack of photometrically precise spectra of planetary surfaces in the region from 1.0 to 2.5 micrometers, where additional important mineral absorptions occur. Recently, a new instrument was developed, and an observational program is underway to provide the required near-infrared spectra. The first, comprehensive near-infrared spectroscopic results for the moon are presented. It is shown that it is equally possible to derive quantitative mineralogical information about the lunar surface by using remotely sensed reflectance spectra as it is by using laboratory reflectance measurements of lunar samples.

Mccord, T. B.↗
NASA NTRS1982

Electromagnetic induction in the moon

The moon constitutes a nonhydromagnetic, but electrically conducting, target for the solar wind whose response reaches a peak as frequency increases and diminishes with further increase in frequency, suggesting the presence of the magnetic quadrupole moment. Magnetometer measurements of induction using Explorer and Apollo instruments are studied from both the harmonic and transient standpoint, and the resulting determination of internal bulk electrical conductivity is discussed. The closeness of the estimated internal temperature to the Ringwood-Essene solidus at 150-250 km depths suggests a layer of enhanced conductivity in lieu of high temperature. A reduced core radius estimate with a one-sigma upper limit of 360 km is reported. The discussion of lunar electrodynamics presented is restricted to the problem of induction, with only passing reference to flow fields and regional electric fields.

Sonett, C. P.↗
NASA NTRS1982

The intercrater plains of Mercury and the Moon: Their nature, origin and role in terrestrial planet evolution: Introduction

The relative ages of various geologic units and structures place tight constraints on the origin of the Moon and the planet Mercury, and thus provide a better understanding of the geologic histories of these bodies. Crater statistics, a reexamination of lunar geologic maps, and the compilation of a geologic map of a quarter of Mercury's surface based on plains units dated relative to crater degradation classes were used to determine relative ages. This provided the basis for deducing the origin of intercrater plains and their role in terrestrial planet evolution.

Leake, M. A.↗
NASA NTRS1982

The intercrater plains of Mercury and the Moon: Their nature, origin and role in terrestrial planet evolution. Geologic map analyses: Correlation of geologic and cratering histories

Geologic map analyses are expanded, beginning with a discussion of particular regions which may illustrate volcanic and ballistic plains emplacement on Mercury. Major attention is focused on the surface history of Mercury through discussion of the areal distribution of plains and craters and the paleogeologic maps of the first quadrant. A summary of the lunar intercrater plains formation similarly interrelates the information from the Moon's geologic and cratering histories.

Leake, M. A.↗
NASA NTRS1981

Earthquakes - on the moon

Information obtained with the Apollo lunar seismic stations is discussed. The four types of natural seismic sources that have been identified are described, viz., thermal moonquakes, deep moonquakes, meteoroid impacts, and shallow moonquakes. It is suggested that: (1) the thermal quakes represent the slow cracking and movement of surface rocks; (2) the deep quakes are induced by the tide-generating force of the earth's gravity; (3) the meteoroids responsible for most of the observed impacts are in the mass range from 1 to 100 kg and are clustered in groups near the earth's orbit; and (4) the shallow quakes are similar to intraplate earthquakes and indicate that the moon is as seismically active as the interior regions of the earth's tectonic plates. The structure of the lunar interior as inferred from seismic signals due to both the last three natural sources and 'artificial' impacts of used spacecraft is examined in detail.

Nakamura, Y.↗
NASA NTRS1983

Should we make products on the moon?

It is pointed out that products from extraterrestrial materials can play a major role in future space operations within the useful lifetime of the first major space station, now in the planning stage. Possible economic advantages regarding the use of such products could be related to the recognition that it takes seven times more energy to get one kilogram from the earth's surface to low earth orbit (LEO) than it does to move one kilogram from the moon's surface to LEO. An analysis regarding the margin of advantage of extraterrestrial materials as been conducted, taking into account equipment and supplies which ust be launched from earth to make the acquisition of extraterrestrial products feasible. The present investigation is concerned with a study of engineering practicality. Attention is given to the transport of processing equipment from LEO to the lunar surface and of lunar products to LEO and the geosynchronous orbit. It is found that lunar oxygen and radiation shielding could possibly be utilized by the turn of the century.

Carroll, W. F.↗
NASA NTRS1984

Morphologic studies of the Moon and planets

The impact, volcanic, and tectonic history of the Moon and planets were investigated over an eight year period. Research on the following topics is discussed: lunar craters, lunar basins, lunar volcanoes, correlation of Apollo geochemical data, lunar geology, Mars desert landforms, and Mars impact basins.

El-Baz, F.↗
NASA NTRS1983

Ice-rich moons and the physical properties of ice

Many of the moons of the outer planets in the solar system consist to a substantial degree of water and other ices. Such ices are thought to make up at least half, by mass, of all condensed material in the outer solar system. The surfaces and interiors of these icy satellites have undergone considerable geologic evolution, and in some cases may still be active today. So that these processes can be understood, certain critical data on the behavior of water and other ices at low (ca. 100 K) temperatures and high (ca. 10 kbar) pressures are needed. Given such data, various techniques for modeling planetary interiors can be tested to see which models best describe the conditions observed on these bodies; such models may then be used to study larger, terrestrial planets.

Consolmagno, G. J.↗
NASA NTRS1984

Conference on the Origin of the Moon

Various topics relating to lunar evolution are discussed. The Moon's ancient orbital history, geophysical and geochemical constraints favoring the capture hypothesis, the site of the lunar core, chemical and petrological constraints, dynamical constraints, and mathematical models are among the topics discussed.

Source record↗
NASA NTRS1984

Megaregolith thickness, heat flow, and the bulk composition of the Moon

Models developed to assess the effects of megaregolith on lunar thermal evolution are discussed. It is confirmed that the two sites where lunar heat flow was measured are probably unrepresentative, with heat flows about 25% higher than regional averages, due to focussing of heat flow towards regions with thin megaregolith. Numerous lines of evidence indicate that the megaregolith is generally 2 to 3 km thick under highlands (which cover about 83% of the total lunar surface), and 1 km thick under maria. In most models, megaregolith thickness is assumed to be roughly 6x greater over highlands than over maria. Based on sparse data for porosity among lunar rock types, and the correlation between thermal conductivity and porosity, it is assumed that megaregolith conductivity is roughly 20 kiloerg s(-1)cm(-1)K(-1), and bedrock conductivity is roughly 7x greater. It is also found that insulation by megaregolith exacerbates the problem of reconciling modest temperatures inferred for the (present) matle with a high rate of heat production; an upper limit of 30 ng/g for the bulk-Moon U content can be derived from this constraint alone.

Warren, P. H.↗