Photometry of the lunar surface during lunar eclipses

The photometric observations of the lunar surface during lunar eclipses were carried out on four nights between 1972 to 1978, using the 91 cm reflector of the Dodaira Station of the Tokyo Astronomical Observatory. The photometry was performed in B-, V-, and R-colours, and arranged in accordance with the angular distance from the centre of the Earth's shadow. The results do not show any large systematic differences between the four nights, showing no support for Danjon's proposition.     

On the history of the lunar orbit

A frequency-dependent model of tidal friction is used in the determination of the time rate of change of the lunar orbital elements and the angular velocity of the Earth. The variational equations consider eccentricity, the solar tide on the Earth, Earth oblateness, and higher-order terms in the Earth's tidal potential. A linearized solution of the equations governing the precission of the Earth's rotational angular momentum and the lunar ascending node is found. This allows the analytical averaging of the variational equations over the period of relative precession which, though large, is necessarily small in comparison to the time step of the numerical integrator that yields the system history over geological time. Results for this history are presented and are identified as consistent with origin of the Moon by capture. This model may be applied to any planet-satellite system where evolution under tidal friction is of interest.     

Photometry of the lunar surface

The photometry of the Moon gives us some information about the properties of the lunar surface. The photometric uniformity of the lunar surface as a scattering screen is determined by the shadow phenomena on small irregularities due to the dust layer covering the whole surface. A small component of light (< 10 %) exhibits the features of the luminescence excited by solar radiations.Paper presented to the NATO Advanced Study Institute on Lunar Studies, Patras, Greece, September 1971.     

Thermoluminescence of the lunar surface

Observations of the lunar luminescence are reported for a dozen of specific Moon features using the line-depth method with a high resolution spectroscopic technique. The data indicate a variation of the Moon proper emission as a function of the phase angle which is interpreted as a proof of the thermoluminescent origin of this emission.     

Regolith history of lunar meteorites

Abstract— The regolith evolution of the lunar meteorites Dhofar (Dho) 081, Northwest Africa (NWA) 032, NWA 482, NWA 773, Sayh al Uhaymir (SaU) 169, and Yamato (Y‐) 981031 was investigated by measuring the light noble gases He, Ne, and Ar. The presence of trapped solar neon in Dho 081, NWA 773, and Y‐981031 indicates an exposure at the lunar surface. A neon three‐isotope diagram for lunar meteorites yields an average solar ²⁰Ne/²²Ne ratio of 12.48 ± 0.07 representing a mixture of solar energetic particles neon at a ratio of 11.2 and solar wind neon at a ratio of 13.8. Based on the production rate ratio of ²¹Ne and ³⁸Ar, the shielding depth in the lunar regolith of NWA 032, NWA 482, SaU 169, and Y‐981031 was obtained. The shielding depth of these samples was between 10.5 g/cm² and >500 g/cm². Based on spallogenic Kr and Xe, the shielding depth of Dho 081 was estimated to be most likely between 120 and 180 g/cm². Assuming a mean density of the lunar regolith of 1.8 g/cm³, 10.5 g/cm² corresponds to a depth of 5.8 cm and 500 g/cm² to 280 cm below the lunar surface. The range of regolith residence time observed in this study is 100 Ma up to 2070 Ma.     

The early geological history of the Moon inferred from ancient lunar meteorite Miller Range 13317

Miller Range (MIL) 13317 is a heterogeneous basalt‐bearing lunar regolith breccia that provides insights into the early magmatic history of the Moon. MIL 13317 is formed from a mixture of material with clasts having an affinity to Apollo ferroan anorthosites and basaltic volcanic rocks. Noble gas data indicate that MIL 13317 was consolidated into a breccia between 2610 ± 780 Ma and 1570 ± 470 Ma where it experienced a complex near‐surface irradiation history for ~835 ± 84 Myr, at an average depth of ~30 cm. The fusion crust has an intermediate composition (Al₂O₃ 15.9 wt%; FeO 12.3 wt%) with an added incompatible trace element (Th 5.4 ppm) chemical component. Taking the fusion crust to be indicative of the bulk sample composition, this implies that MIL 13317 originated from a regolith that is associated with a mare‐highland boundary that is KREEP‐rich (i.e., K, rare earth elements, and P). A comparison of bulk chemical data from MIL 13317 with remote sensing data from the Lunar Prospector orbiter suggests that MIL 13317 likely originated from the northwest region of Oceanus Procellarum, east of Mare Nubium, or at the eastern edge of Mare Frigoris. All these potential source areas are on the near side of the Moon, indicating a close association with the Procellarum KREEP Terrane. Basalt clasts in MIL 13317 are from a very low‐Ti to low‐Ti (between 0.14 and 0.32 wt%) source region. The similar mineral fractionation trends of the different basalt clasts in the sample suggest they are comagmatic in origin. Zircon‐bearing phases and Ca‐phosphate grains in basalt clasts and matrix grains yield ²⁰⁷Pb/²⁰⁶Pb ages between 4344 ± 4 and 4333 ± 5 Ma. These ancient ²⁰⁷Pb/²⁰⁶Pb ages indicate that the meteorite has sampled a range of Pre‐Nectarian volcanic rocks that are poorly represented in the Apollo, Luna, and lunar meteorite collections. As such, MIL 13317 adds to the growing evidence that basaltic volcanic activity on the Moon started as early as ~4340 Ma, before the main period of lunar mare basalt volcanism at ~3850 Ma.     

Large-scale evolution of the lunar surface

The first part of the paper describes the relationship between the erosional stage of craters and the crater areal density. It is shown that class-2 and -3 craters are progressively more abundant as the crater areal density increases, while craters of class 4 and 5 are more abundant with decreasing crater areal densities. A geological model is proposed, in which the class of a newly foormed crater is 1. As time progresses, erosional agents will increase the class of the crater to class 2, then 3, and, in some cases, to 4. The length of time between classification steps is not known in terms of years, but is equivalent to the time necessary for the crater density to increase by 2 to 8 craters per unit area for creaters larger than 10 km, and by 10 to 20 for craters larger than 3.5 km. Craters of class 5 and some of class 4 are not formed by the same erosional agents, but are catastrophic, caused either by a mare-producing impact or by flooding of mare material.The second part of the paper presents a method for relatively dating large lunar areas. The method uses the model previously developed. A relative time sequence is constructed using the density of craters of classes 1, 2, and 3 and the percentage of these which is of class 1. As an example, 18 large areas are defined on the lunar near side and are put in temporal order. Mare Serenitatis appears to have the youngest terrain, and an area southwest of the Rupes Altai appears to have the oldest.In the final part of the paper a geological model is developed in order to explain age differences in the terrae. The model calls for rejuvenation of lunar terrains, caused by the seismic waves and ballistic sedimentation resulting from large impacts. The area surrounding Mare Orientale is cited as an example of a terrain so affected. A similar effect on the terrae of the near side could explain the apparent age relationships measured.     

The sunlit lunar surface

Directional infrared emission from the sunlit lunar surface is determined for the thermal meridian and as a function of observer elevation and azimuth angles at three Sun elevation angles. A study of selected mare sites at full Moon suggests that brightness temperatures are relatively insensitive to changes in certain surface parameters, such as the photometric function, emissivity, and thermophysical properties of the soil. The observed deviations from predictions for an average surface can be accounted for by changes in surface roughness.Deceased 12 January, 1971.     

Dielectric properties of lunar surface

Measurements of the dielectric characteristics of lunar soil samples are analyzed in the context of dielectric theory. It has been shown that the real component of the dielectric permittivity and the loss tangent of rocks greatly depend on the frequency of the interacting electromagnetic field and the soil temperature. It follows from the analysis that one should take into account diurnal variations in the lunar surface temperature when interpreting the radar-sounding results, especially for the gigahertz radio range.     

Post-sunset cooling behavior of the lunar surface

Differential infrared flux scans at 22m have been made across the nighttime lunar surface over a range of phases before and after new Moon. The differential chopping technique effectively cancels atmospheric emission in the beam path but records the flux difference between adjacent resolution elements on the lunar disk. The scans show that the brightness temperature gradient across the highlands after sunset is much greater than that across the western maria. The large gradients consistently disappear approximately 3.5 days after sunset. The post-sunset enhancement could be due to surface roughness in the highlands or to a significant surface rock population with a mean size of approximately 0.5 m. The effect can be seen in the 10m measurements of other investigators, but its global nature was not detected in their limited data sets.     

Average chemical composition of the lunar surface

The available data on the chemical composition of the lunar surface at eleven sites (3 Surveyor, 5 Apollo and 3 Luna) are used to estimate the amounts of principal chemical elements (those present in more than about 0.5% by atom) in average lunar surface material. The terrae of the Moon differ from the maria in having much less iron and titanium and appreciably more aluminum and calcium.Paper dedicated to Prof. Harold C. Urey on the occasion of his 80th birthday on 29 April 1973.     

A geological interpretation of the lunar surface

This interpretation of lunar surface features is based on the differentiation of siliceous and basaltic substances similar to those of the earth. Our hypothesis is that lunar maria are composed of basaltic matter similar to that of terrestrial ocean basins, and that the lunar continents (bright regions) are composed of siliceous blocks.     

Cosmic ray interactions with lunar materials: Nature and composition of species formed

The solar and galactic cosmic rays interact directly with lunar surface materials, and the dominant nature of interactions is essentially the complete absorption of corpuscles. These corpuscles damage the lattice structure, and induce a complex set of reactions in the materials producing various species. The cosmic ray damage of the lattice would not produce an amorphous layer, similar to that produced by the solar wind, because the solar wind erosion rate is faster than the cosmic ray-induced amorphous layer formation rate. The species formation rate considered in this paper are those produced by protons, the dominant component of cosmic rays. Protons produce H, H₂, OH, H₂O, and hydrogenated species of carbon, nitrogen, sulfur, etc. These species, while migrating in the material, encounter oncoming cosmic ray corpuscles, and undergo a complex set of reactions. Although a variety of species are produced by protons, the dominant contributor to the atmosphere is H₂. The H₂ flux (molecules cm^–2 sec^–1) is about 1.5 × 10⁵ as compared to the H flux of 8.4 × 10¹ and the H₂O flux of 4.6 × 10^–2. These fluxes are about 10^–3 smaller than the fluxes of the same species produced by the solar wind protons. Thus the contributions of the cosmic ray-induced species to the atmosphere is very small compared to the solar wind-induced species. Although simulated experiments showed high concentractions of OH and H₂O in the terrestrial materials of lunar type, these species concentrations in the lunar materials under the lunar environment is much smaller than those observed in the simulated experiments.     

Cosmic ray propagation and the star formation history of NGC 1961

We present new radio continuum data at four frequencies for the supermassive, peculiar galaxy NGC 1961. These observations allow us to separate the thermal and non-thermal radio emission and to determine the non-thermal spectral index distribution. This spectral index distribution in the galactic disc is unusual: at the maxima of the radio emission the synchrotron spectrum is very steep, indicating aged cosmic ray electrons. Away from the maxima the spectrum is much flatter. The steep spectrum of the synchrotron emission at the maxima indicates that a strong decline of the star formation rate has taken place at these sites. The extended radio emission is a sign of recent cosmic ray acceleration, probably by recent star formation. We suggest that a violent event in the past, most likely a merger or a collision with an intergalactic gas cloud, has caused the various unusual features of the galaxy.     

Origin and transportation history of lunar breccia 14311

In this paper, we compare the U‐Pb zircon age distribution pattern of sample 14311 from the Apollo 14 landing site with those from other breccias collected at the same landing site. Zircons in breccia 14311 show major age peaks at 4340 and 4240 Ma and small peaks at 4110, 4030, and 3960 Ma. The zircon age patterns of breccia 14311 and other Apollo 14 breccias are statistically different suggesting a separate provenance and transportation history for these breccias. This interpretation is supported by different U‐Pb Ca‐phosphate and exposure ages for breccia 14311 (Ca‐phosphate age: 3938 ± 4 Ma, exposure age: ~550–660 Ma) from the other Apollo 14 breccias (Ca‐phosphate age: 3927 ± 2 Ma, compatible with the Imbrium impact, exposure age: ~25–30 Ma). Based on these observations, we consider two hypotheses for the origin and transportation history of sample 14311. (1) Breccia 14311 was formed in the Procellarum KREEP terrane by a 3938 Ma‐old impact and deposited near the future site of the Imbrium basin. The breccia was integrated into the Fra Mauro Formation during the deposition of the Imbrium impact ejecta at 3927 Ma. The zircons were annealed by mare basalt flooding at 3400 Ma at Apollo 14 landing site. Eventually, at approximately 660 Ma, a small and local impact event excavated this sample and it has been at the surface of the Moon since this time. (2) Breccia 14311 was formed by a 3938 Ma‐old impact. The location of the sample is not known at that time but at 3400 Ma, it was located nearby or buried by hot basaltic flows. It was transported from where it was deposited to the Apollo 14 landing site by an impact at approximately 660 Ma, possibly related to the formation of the Copernicus crater and has remained at the surface of the Moon since this event. This latter hypothesis is the simplest scenario for the formation and transportation history of the 14311 breccia.     

Contribution of tidal dissipation to lunar thermal history

The possible contributions of tidal heating to lunar thermal history are investigated. Analytic determinations of tidal dissipation in a homogeneous, incompressible Moon and in a two-layer Moon with a soft core and rigid mantle are given as a function of position in the Moon and as a function of Earth-Moon separation. The most recent information on the historical values of the lunar obliquity is employed, and we present results for the constant values of orbital eccentricity of e = 0.0 and e = 0.055. For a simplified orbital evolution and a dissipation factor Q = 100, the total increase in the mean lunar temperature for the homogeneous case does not exceed several tens of degrees. For the two-layer models the local dissipation may be enhanced over that of the homogeneous Moon by a factor of 5 for a core radius of 0.5 lunar radii and by a factor of 100 for a core radius of 0.95 lunar radii. The corresponding factors for the total dissipation are 3 and 15 for the two values of core radii, respectively. We conclude that tidal contributions to lunar thermal history are probably not important. But under special circumstances the enhanced dissipation in a two-layer Moon could have led to a spectacular thermal event.     

The impact-theory interpretation of the distribution of Maria on the lunar surface

The satellite impact interpretation of the surface distribution of lunar maria is presented according to Barricelli and Metcalfe (1969). It is emphasized that the formation of molten rock (lava) which, according to the Apollo 11 findings, seems to have been the origin of the material of which maria are composed, can be the result of heat developed by the impacts which created the respective maria (Gilbert 1893) and does not necessarily imply a volcanic or internal origin of this material.The distribution of mascons and some of its possible interpretations are discussed.Present address: Oslo Universitet, Dept. of Mathematics, Blindern, Norway.     

Structural disturbances of the lunar surface caused by spacecraft

From the lunar surface survey performed with a narrow-angle camera of the Lunar Reconnaissance Orbiter (LRO) spacecraft, the distributions of the phase ratios of the Apollo 11 and 12 landing sites and the Ranger 9 impact site were mapped. In the acquired images, the traces of the structural disturbances of the lunar regolith layer caused by the jet flows are seen. In the Ranger 9 impact site, one can see the crater of about 15 m across with a ray system, which is hardly noticeable in the brightness picture, but has a high contract in the phase ratio picture. The character of the photometric anomaly of the rays of this crater shows that they are formed by the ejected stones composing the rugged relief, which induces a strong shadow effect. At the same time, the influence of jet flows from the rocket engines smooths the relief and leads to the photometric anomaly of the opposite sign. The estimate of the maturity degree of the lunar regolith in the Apollo 11 and 12 landing sites obtained from the SELENE spectral survey suggests that the depth of the influence of the rocket engines on the soil is small, and the surface of the impact crater formed by the Ranger 9 spacecraft contains a large amount of the immature soil.     

Spectroscopic remote sensing of lunar surface composition

The various regions of the electromagnetic spectrum currently being used to determine the composition of the lunar surface remotely are reviewed. The advantages and disadvantages of using each region are pointed out, and limits are set on the kind and amount of information that can be obtained. It is concluded that it would be most useful to apply all of these techniques to the problem of remotely exploring the Moon because of the complementary nature of the data obtained.Paper presented to the NATO Advanced Study Institute on Lunar Studies, Patras, Greece, September 1971.     

Observations of water vapor ions at the lunar surface

The Apollo 14 Suprathermal Ion Detector Experiment observed a series of bursts of 48.6 eV water vapor ions at the lunar surface during a 14-h period on March 7, 1971. The maximum flux observed was 10⁸ ions cm^–2 s^–1 sr^–1. These ions were also observed at Apollo 12, 183 km to the west. Evaluation of specific artificial sources including the Apollo missions and the Russian Lunokhod leads to the conclusion that the water vapor did not come from a man-made source. Natural sources exogenous to the Moon such as comets and the solar wind are also found to be inadequate to explain the observed fluxes. Consequently, these water vapor ions appear to be of lunar origin.Paper dedicated to Prof. Harold C. Urey on the occasion of his 80th birthday on 29 April 1973.