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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Tidal friction and the early history of the moon's orbit

The present work investigates the consequences implied by various rheological models of the early earth for the orbital history of the moon subsequent to its formation. Models of the earth that yield small tidal angles, such as low-viscosity models, imply that the moon never orbited in the earth's equatorial plane, thereby ruling out an equatorial origin for the moon. A high-viscosity model is shown to permit the moon to originate in the equatorial plane and still account for the present-day characteristics of the moon's orbit.

Rubincam, D. P.↗
NASA NTRS1975

Earth-moon system: Dynamics and parameter estimation

A theoretical development of the equations of motion governing the earth-moon system is presented. The earth and moon were treated as finite rigid bodies and a mutual potential was utilized. The sun and remaining planets were treated as particles. Relativistic, non-rigid, and dissipative effects were not included. The translational and rotational motion of the earth and moon were derived in a fully coupled set of equations. Euler parameters were used to model the rotational motions. The mathematical model is intended for use with data analysis software to estimate physical parameters of the earth-moon system using primarily LURE type data. Two program listings are included. Program ANEAMO computes the translational/rotational motion of the earth and moon from analytical solutions. Program RIGEM numerically integrates the fully coupled motions as described above.

Breedlove, W. J., Jr.↗
NASA NTRS1977

The Soviet-American Conference on Cosmochemistry of the Moon and Planets, Part 1

The basic goal of the conference was consideration of the origin of the planets of the solar system, based on the physical and chemical data obtained by study of the material of the moon and planets. Papers at the conference were presented in the following sessions: (1) Differentiation of the material of the moon and planets; (2) The thermal history of the moon; (3) Lunar gravitation and magnetism; (4) Chronology of the moon, planets, and meteorites; (5) The role of exogenic factors in the formation of the lunar surface; (6) Cosmochemical hypotheses about the origin and evolution of the moon and planets; and (7) New data about the planets Mercury, Venus, Mars, and Jupiter.

Pomeroy, J. H.↗
NASA NTRS1977

Riddles about the origin and thermal history of the moon

Magmatic differentiation of the moon's interior, confirmed through calculations of thermal history, was studied. It appears that differentiation was a result of the moon's initial temperature whose origin remains unknown. In solving this problem, convective models of the moon were considered as well as a two layered differentiated model of the moon, operative over the past 3.5 billion years. The high content of long lived radioactive elements present was investigated in explaining the moon's current thermal properties. The controversy concerning the true nature of magmatic differentiation continues to be unsolved.

Levin, B. Y.↗
NASA NTRS1977

Moon-Mercury - Large impact structures, isostasy and average crustal viscosity

It is shown that Mercury's surface has only 70% as many large craters (of at least 200 km in diameter) as the moon. The density of Mercurian impact craters having diameters over 400 km is 30% of that of the moon, and for craters with diameters between 400 and 700 km, Mercurian density is 21% of that of the moon. The size-frequency distribution curve of Mercury is the same as the lunar cumulative -2 slope. The Mercurian curve, however, lies well below the 10% surface saturation level of the lunar curve. This may indicate that the old, heavily-cratered Mercurian terrain is not presently in a state of cratering equilibrium. The differences in crater and basin densities observed between Mercury and the moon may be functions of crater-production rates or of different crustal histories. The total isostatic compensation of impact craters having diameters of about 800 km suggests that the average viscosity of the Mercurian crust during approximately the past 4 eons was the same as that of the moon.

Schaber, G.↗
NASA NTRS1983

Workshop on Pristine Highlands Rocks and the early History of the Moon

Oxide composition of the Moon, evidence for an initially totally molten Moon, geophysical contraints on lunar composition, random sampling of a layered intrusion, lunar highland rocks, early evolution of the Moon, mineralogy and petrology of the pristine rocks, relationship of the pristine nonmore rocks to the highlands soils and breccias, ferroan anorthositic norite, early lunar igneous history, compositional variation in ferroan anosthosites, a lunar magma ocean, deposits of lunar pristine rocks, lunar and planetary compositions and early fractionation in the solar nebula, Moon composition models, petrogenesis in a Moon with a chondritic refractory lithophile pattern, a terrestrial analog of lunar ilmenite bearing camulates, and the lunar magma ocean are summarized.

Longhi, J.↗
NASA NTRS1984

Origin of the Moon: In search of the holy grail

The Moon's origin could be deduced with certainty if its bulk chemistry were known. However, determination of this chemistry is difficult because of the profound and complex redistribution of elements that occurred in the outer portions of the Moon during crystallization of the magma ocean. The compositions of 23 varieties of volcanic glass, erupted from depths approaching 300 miles, were used to predict the chemistry of a special glass (genesis glass) having a direct link to primordial lunar matter. A sample of glass with the predicted composition was discovered. This allows a new estimate to be made of the Moon's bulk composition. The data indicate that the Moon shares some intriquing chemical similarities with the Earth's mantle. Both genesis glass and lunar gas are furnishing definitive data on the Moon's composition and origin.

Delano, J. W.↗
NASA NTRS1984

Bulk composition of the Moon in the context of models for condensation in the solar nebula

The FeO content of the Moon is substantially higher than the present FeO content of the Earth's mantle. If the Moon formed by fission from the Earth's mantle, then the conclusion that the Earth's mantle must have been much richer in FeO at the time of fission appears firm. If the Moon formed independently in geocentric orbit, then the FeO contents of the two bodies should be similar, because both would be accreting from the same source of silicate material. Therefore, Earth's mantle at the time of lunar formation probably had an FeO content quite similar to the present FeO content of the Moon. This conclusion, if valid, has profound implications in two areas: (1) the differentiation history of the Earth's mantle and core; and (2) the processes responsible for governing the bulk compositions of the terrestrial planets. If Earth had more FeO than previously thought, then the composition differences between Earth and Mars are less than previously believed. This suggests that condensation temperature and heliocentric distance may have been less important in governing planetary compositions and other mechanisms, including iron/silicate fractionation may have been more important. The implication of this model for the compositions of the Moon and the other terrestrial planets are discussed.

Goettel, K. A.↗
NASA NTRS1984

The I-Pu-Xe age of the Moon

The Rb-Sr analyses of some lunar samples which indicate that the Moon is close to the age of primitive meteorites are only reliable to within about 100 m.y. A potentially more precise chronometer is the I-Pu-Xe system. I129 has a 17 m.y. halflife and decays to Xe129; Pu244, with an 82 m.y. halflife, produces Xe131 to Xe136 in fission. The I129/Pu244 ratio has a halflife of 21 m.y. Xenon retention for the Earth could have begun as late as the event that gave birth to the Moon. For the Moon, it is hard to imagine that xenon retention could have begun before re-accretion of the fissioned (and initially dispersed?) material, particularly if that material got hot enough to account for the depletion of the volatile elements. Thus, if fission model are correct, xenon retention in the Earth certainly began no later than in the Moon, and possibly began earlier. Therefore, the I-Pu-Xe system is only marginally consistent with a fission origin. If further study confirms that the I/U ratio of the Moon is .01 or less, or if gas-rich lunar highland breccias with higher ratios of I129 to Pu244 are found, it would be difficult to explain the results in an earth-fission model of lunar origin.

Swindle, T. D.↗
NASA NTRS1984

The Moon's orbit history and inferences on its origin

A frequency dependent model of tidal friction was used to determine the evolution of the Earth-Moon system. The analysis considers the lunar orbit eccentricity and inclination, the solar tide on the Earth, Earth oblateness, and higher order terms in the tidal potential. A solution of the equations governing the precession of the Earth's rotational angular momentum and the lunar ascending node is found. The history is consistent with a capture origin for the Moon. It rules out the origin of the Moon by fission. Results are shown for a range of assumed values for the lunar tidal dissipation. Tidal dissipation within the Moon, during what would be the immediate postcapture period, is shown to be capable of significantly heating the Moon. The immediate postcapture orbit has a periapsis within the Earth's Roche limit. Capture into resonance with the Earth's gravitational field as this orbit tidally evolves is suggested to be a mechanism to prevent so close, an approach. It is shown that the probability of such capture is negligibly small and alternative hypotheses for the survival of the Roche limit passage is offered.

Conway, B. A.↗
NASA NTRS1984

A numerical investigation of planetesimal collision trajectories with a Moon accumulating in Earth orbit

In the scenario of lunar origin in which the Moon is assumed to have accreted most of its mass while in orbit about the Earth, ismals on the accrea knowledge of the relative impact rates of heliocentric planetting Earth and Moon is essential for any attempt to establish dynamical constraints on lunar origin. Numerical integrations of the regularized equations of motion for four bodies (Sun, Earth, Moon, planetismal) were done. A planetismal impact trajectory was calculated by assuming that the planetismal has hit the surface of the Moon at an assumed location, traveling in an assumed direction, and with an assumed impact speed. Next, the equations of motion were numerically integrated backward in time in order to determine from where the planetismal has come. In this way those volumes in heliocentric orbital element space which contribute trajectories that directly impact the Moon.

Cox, L. P.↗
NASA NTRS1984

The origin of the Moon

Bulk density alone shows that the Moon is depleted in metallic FeNi relative to the Earth or to chondritic meteorites. This depletion implies that the Moon formed not from chondrites but from differentiated material. Origin of the Moon by fission from the Earth offers a simple explanation for its depletion in FeNi, but this mechanism seems unlikely because of associated dynamical difficulties. Lunar volatile element depletions were invoked in support of fission, but volatile contents of eucritic meteorites are similarly low and the eucrites did not form by Earth fission. A more plausible origin of the Moon is accretion from the circumterrestrial swarm. The low FeNi content of the Moon is understood if the mean size of interplanetary silicate particles was much smaller than that for metal particles, since this would have led to preferential capture of silicates into Earth orbit, but the question arises whether the mean particle size of the metallic particles was great enough to prevent their capture into the swarm.

Wasson, J. T.↗
NASA NTRS1989

Crustal diffusion of gases out of Mercury and the moon

An upper limit to the rate of diffusion of sodium and potassium out of Mercury and the moon was calculated, and the resulting flux was compared to that required to maintain the known exospheres. It was found that diffusion rates are inadequate by 12 orders of magnitude on the moon and 9 orders of magnitude on Mercury for diffusion out of orthoclase minerals. Diffusion will be more rapid out of pure glass by five to six orders of magnitude and out of shocked basalt by an amount depending on the microstructure of the mineral. The observed abundance and distribution of volatiles in small glass spherules on the moon indicates that diffusion is very inefficient after solidification and cooling. At Mercury, the limitation on sodium flux to the atmosphere is shown to be the rate at which new regolith is created. The discrepancy between the observed column abundance of sodium in the Mercurean atmosphere and the known sources may indicate that either Mercury's crust has a larger volatile content than the moon or that a recycling mechanism exists in the Mercurean atmosphere which is not present for the moon.

Killen, R. M.↗
NASA NTRS1989

Science opportunities in the human exploration of moon

Human exploration of the moon will open up science opportunities not only in lunar science, but also in astronomy and astrophysics, life science, solar and space physics, earth science, and even evolutionary biology. These opportunities may be categorized as those involving study of the moon itself, those in which the moon is used as a platform for investigations, and those conducted in transit between earth and the moon. This paper describes some of these opportunities, and calls on the science community to continue and expand its efforts to define the opportunities, and to work toward their inclusion in plans to return humans permanently to the moon.

Pilcher, Carl B.↗
NASA NTRS1992

Why explore the moon?

An overview is presented of reasons to pursue exploration of the moon, including the expansion of human settlements beyond earth, the scientific benefits from the exploration of the moon, the utilization of the moon as a research laboratory, and the opening of the resources of near-earth space. Consideration is also given to Mars exploration in which the moon is used principally as a testbed. Attention is given to the current work by the Office of Exploration, whose effort is aimed at comprehending the first 'waypoint' in a long term strategy for moving toward the moon and Mars.

Duke, Michael B.↗
NASA NTRS1993

Production of O2 on the Moon: A lab-top demonstration of ilmenite reduction with hydrogen

Estimates of the costs of transporting materials from Earth to the Moon are around $25,000 per pound. Therefore, it is imperative that we learn to utilize the resources on the Moon to partially offset these 'astronomical' expenses. The production of oxygen on the Moon utilizing indigenous materials is crucial to the establishment and development of an autonomous lunar colony. Besides obvious biologic needs, this lunar liquid oxygen (LLOX) could result in tremendous cost savings on fuel for effective transportation systems, particularly with its export to low-Earth orbit. Over 20 different process concepts were proposed and evaluated for the production of oxygen from lunar materials. Simplicity, low energy, easily attainable feedstock, and low resupply mass are the keywords for the process(es) which will ultimately be selected for the initial production of oxygen on the Moon. One of these schemes, which has received considerable study to date, is the hydrogen reduction of ilmenite. In fact, Carbotek, Inc. (Houston, TX) patented an ilmenite, hydrogen-reduction technique involving a three-stage, fluidized-bed process for the production of LLOX. A lab-top demonstration unit of the basic concepts of this oxygen generation process that was constructed by our group at the University of Tennessee is explained. It utilizes many of the principles which must be addressed in designing an effective production plant for operation on the Moon.

Taylor, Lawrence A.↗
NASA NTRS1994

Infrared astronomy from the Moon

The purpose of this paper is to exhibit the advantages and limitations to infrared astronomical observations form the moon. The most obvious apparent advantage is the lack of a lunar atmosphere; radiation arriving from the universe is neither extinguished nor refracted as it approaches the lunar surface. However, the Earth's atmosphere's protection against cosmic rays is also lost, and infrared detectors are highly sensitive to irradiation by energetic particles. A second apparent advantage is the relative ease with which beams from an array of telescopes can be interferometrically combined; again the vacuum environment with constant refractive index of unity throughout, permits combination without phase delay across the entire spectral range. But thermal radiation from optical components and stray radiation from the lunar environment, just outside the light path, tend to lessen that advantage, except in narrow-spectral-band spatial interferometry, in which only the radiation in individual spectral lines is mapped, and broad-band thermal emission can be effectively filtered out. On the Moon's night side, and in polar craters on the Moon, radiative cooling should permit the attainment of high sensitivity with large telescopes. Just as the proposed Edison spacecraft primary mirror is expected to reach temperatures around 40 K, so also large lunar primary mirrors might be expected to reach temperatures in that range, making the zodiacal glow the main source of noise at wavelengths shortward of 25 micrometers. The slow rota tion of the Moon, and the lack of vibrations from natural sources such as winds, should provide advantages in guiding on specific astronomical sources. To learn as much as possible about the difficulties of remote observations in a hostile environment, Antarctic observatories should be used as test beds for the rigors of lunar observations. The strenuous requirements for successful astronomical observations from the South Pole are similar to those expected to be encountered in observations conducted from the Moon.

Harwit, Martin↗
NASA NTRS1994

What would we miss if we characterized the Moon and Mars with just planetary meteorites, remote mapping, and robotic landers?

Exploration of the Moon and planets began with telescopic studies of their surfaces, continued with orbiting spacecraft and robotic landers, and will culminate with manned exploration and sample return. For the Moon and Mars we also have accidental samples provided by impacts on their surfaces, the lunar and martian meteorites. How much would we know about the lunar surface if we only had lunar meteorites, orbital spacecraft, and robotic exploration, and not the Apollo and Luna returned samples? What does this imply for Mars? With martian meteorites and data from Mariner, Viking, and the future Pathfinder missions, how much could we learn about Mars? The basis of most of our detailed knowledge about the Moon is the Apollo samples. They provide ground truth for the remote mapping, timescales for lunar processes, and samples from the lunar interior. The Moon is the foundation of planetary science and the basis for our interpretation of the other planets. Mars is similar to the Moon in that impact and volcanism are the dominant processes, but Mars' surface has also been affected by wind and water, and hence has much more complex surface geology. Future geochemical or mineralogical mapping of Mars' surface should be able to tell us whether the dominant rock types of the ancient southern highlands are basaltic, anorthositic, granitic, or something else, but will not be able to tell us the detailed mineralogy, geochemistry, or age. Without many more martian meteorites or returned samples we will not know the diversity of martian rocks, and therefore will be limited in our ability to model martian geological evolution.

Lindstrom, M. M.↗