Moon: ‘ghost’ craters formed during mare filling

This paper discusses formation of pathological cases of crater morphology due to interaction of craters with molten lavas. Terrestrial observations of such a process are discussed. In lunar maria, a number of small impact craters (D < 10 km) may have been covered by thin layers of fluid lavas, or formed in molten lava. Some specific lunar examples are discussed, including unusual shallow rings resembling experimental craters deformed by isostatic filling.Paper dedicated to Professor Harold C. Urey on the occasion of his 80th birthday on 29 April 1973.     

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.     

Сопоставление модели карлсона с моделью сплошной среды

, (1962, 1963) . , (1) (2) .     

Some fundamental elements of universe mechanics

An essential part in the mechanics under study is taking into consideration the effect of motions of the Universe objects upon that of an individual one surrounded by them including those infinitely far from it. Only macro-objects of the Universe are meant here.

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Zusammenfassung Ein wesentlicher Bestandteil der Mechanik unter unserer Betrachtung ist die Berechnung des Einflusses auf die Bewegung eines individuellen Objektes von Bewegungen der Universum Objekte die es umringen einschließlich jene Objekte, die unendlich entfernt sind. Nur Makroobjekte des Weltalles sind in der Absicht dabei.

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О природе всплесков γ-излучения

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εлектроны космических лучей радиогало галактики

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О колебаниях хвоста магнитосферы в приБлижении квазигидро динамики

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ОJ 287: Поляризационное и фотометрическое поведение В 1971–1976 гг

J 287 1972–1976. , . . J ( ), () . (₀=80°) . J 287 ¶ . p=42.8%, ₀=101°. (50%).     

Critical inclinations in planetary problems

The general conception of the critical inclinations and eccentricities for theN-planet problem is introduced. The connection of this conception with the existence and stability of particular solutions is established. In the restricted circular problem of three bodies the existence of the critical inclinations is proved for any values of the ratio of semiaxes . The asymptotic behaviour of the critical inclinations as 1 is investigated.

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Оь излучении звезд типа Т Тельца в далеком ельтрафиоле те

, oqn ANS (1500–3300 Å) , I , 3–15 . , <2000 Å nepexo , 1.5 MB . ₀ , . .     

Имп␣льсное γ-излучение нейтронных, коллапсирующих qiх qi qsверхновых qzвезд

qp qz : (1) -, qi , (2) - (R=0.01–0.1R ) (3) - . qs. (1) - 0.1 10^–4 cm ^–2, . - . (2) 10⁸ . . 10^42–43 , (25 ). 10% - (0.1 ). , , , , , . . (3) , , - . . (2×10⁴¹ ) (10²¹ ). - 10³⁸–10³⁹ , 0.25 . , , qq . - , , .

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The following three mechanisms of generation of gamma-ray bursts at advanced phases of stellar evolution are considered; (1) gamma-ray bursts as a result of absorption of neutrino propagating through the envelope of a collapsing star, (2) gamma-ray burst due to thermal radiation of external layers of a compact star (R=0.01–0.1R ) heated by powerful shock wave, and (3) gamma-ray burst as a consequence of possible ejection of matter from neutron star at some active phases of its evolution. In the case (1) the gamma-ray flux at the top of the Earth's atmosphere is about 10^–4 (0.1 MeV photons) cm^–2, if a collapsing star is at Galactic distance (10 kpc). It is considerably less than observed one. The observations of such gamma-bursts however would be an important supplement to the direct detection of neutrino radiation from collapsing stars. In the case (2) external layers of a star are heated up to 10⁸ K. As a result we have a short pulse of thermal radiation with total energy of the order of 10^42–43 erg. The main fraction of the radiation is in the X-ray ( 25 keV), about 10% of total energy being radiated in gamma-ray ( 0.1 MeV). The energy of such a burst is sufficient for explaining observed gamma-bursts provided the supernova outburst probably takes place in our Galaxy and as a result we have some trouble with explanation of observed frequency and spectra of gammabursts. In the case (3) ejection from neutron star of chemically nonequilibrium matter results in the intensive gamma-radiation in consequence of superheavy nuclei fission followed by beta-decays and radiative captures of free neutrons. The ejection of matter from neutron stars may be connected with observed jumps of pulsar's periods. The total ejected mass ( 10²¹ g) can be evaluated from increase of kinetic energy ( 2×10⁴¹ erg.) of Crab nebula filaments. The resulting theoretical energy of gammabursts is of the order of 10^38–39 erg. It is in accordance with observations provided the mean distance of gamma-ray sources is about 0.25 kpc. Contrary to the supernova-outburst mechanism in this case we have probably no troubles with frequency and spectra of gamma-bursts. Among the three mechanisms considered above ejection of matter from neutron stars seems to be a more suitable one for explanation of observations.

     

Stability of the libration points of a rotating triaxial ellipsoid

The problem of stability of the equilibrium points (the libration points) in the problem of motion of a mass point in the neighbourhood of a rotating triaxial ellipsoid is investigated in the strict sense.In the plane of parameters, depending on the form and dynamical characteristics of the ellipsoids, the regions of stability and instability of the libration points are obtained.It is shown that the libration points of the ellipsoids, the form and dynamical characteristics of which are close to the planets of the solar system, are stable.

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( ) . , , . , , , .

     

Возможный механизм радиоизлучения пульсаров

, , , , , . , , . - . — , , .     

Индуцированное комптоновское рассеяние изотропного излучения релятивистскими электронами

, kT _b mc ² . . , , . E ^–5, - E ², mc ²(kT /mc ²)^1/7. , (>2.10⁵ cm ^–3) . , -, , .     

Le développement du potentiel dans le cas d'une densité analytique

The potential of a body of revolution is expanded in a series of spherical functions. It is proved that, for a body with analytical density limited by an analytical surface the coefficients of expansion decrease in geometrical progression.

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Спектр и поляризация источника синхротронного излучения при релятивистском разлете его компонент

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Радиоизлучение Быстрых космических ионов

, . () . , , , . ( ), , , . . (2.7). ( ₁ k ₁ ,V — , — .) (k ₁) (k) §2 ( (2.14)). , (3.6) (3.4), (3.8) . (3.9)–(3.13) ( (3.9), (3.10) (3.11) , (3.12)–(3.13) ). (3.14), (3.16)–(3.19). - . (3.15). ( (4.14)–(4.15)). (4.23)–(4.25). (4.26)–(4.28). §5. , . ((5.5)–(5.6)). , . (5.10) .     

Об устойчивости лагранжевых решений пространственной эллиптической задачи трех тел

. . ,e, , . . e, . , .

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Stability of the librational triangular points of the three-dimensional elliptic restricted three-body problem is studied. The problem is solved in the non-linear statement at the small values of eccentricity.For all values ofe, , besides ones which correspond to the resonances of the third and the fourth order the librational points are stable taking into account the terms up to the fourth order in the normal form of the Hamiltonian function of the perturbed motion.At sufficiently smalle and the non-stability in sense of Liapunov has been proved. The approximate equations of the boundary of the stability area in the planee, has been obtained. The cause of the non-stability is an equality of the rotational period of the principal attracting masses in the elliptic orbit and the period of oscillation of indefinitely small mass along the direction perpendicular to the plane of their motion.

     

Orientation of interstellar and interplanetary grains

The explicit expressions for the orientation distribution function of interstellar and interplanetary dust grains in the anisotropic corpuscular or radiation fluxes, with consideration for the magnetic field influence, are obtained. An orientation is shown to be possible in a medium having an anisotropic temperature, which is usually the case for a non-equilibrium plasma in a magnetic field. It is noted that the small inhomogeneous dust grains should possess a specific rotation of polarization. The orientation of these dust grains is considered. The time required for the orientation is estimated. A possibility of explaining the interstellar polarization and polarization of the cometary radiation is discussed.

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Parameters critical to the morphology of fluidization craters

The anomalously high number of craters with diameter less than 2.8 km, the igneous nature of rocks from the Apollo landing sites, and the possibility of outgassing magmas in the lunar crust, suggest that fluidization may be a viable mechanism for producing many of the smaller lunar craters, Fluidization craters were formed in the laboratory by blowing gas through various thicknesses of particulate material. Gas pressure, regolith thickness, and the duration of gas streaming were controlled over practical experimental limits and compared with the resultant crater morphology. Low to moderate fluidization pressures on coarsely crushed limestone (Mø = 0.40, So = =0.50) with low cohesion (ø - 43°) produced bowl shaped, basin shaped, and flat bottomed craters. Bowl shaped craters change into basin shaped and/or flat bottomed craters with long durations of gas streaming. Cone, funnel, and flat-funnel shaped craters are indicative of high fluidization pressures. Craters formed in finely crushed limestone (Mø - 1.55, So - 0.85) that is electrostatically charged by the streaming gas, are flat bottomed. Terraced craters develop from slumping during and after the discontinuation of gas flow. Central mounds inn terraced craters result from slumping into a confined space. In particulate material, fluidization craters have high circularity and axial symmetry, similar to those produced by impact. The use of an impact model and crater morphology (normal, flat bottomed, and concentric) for estimating lunar regolith depth is questioned because similar craters can be produced by fluidizationn processes in a thicker regolith.On leave at the Earth Physics Branch, Dept. of Energy, Mines and Resources, Ottawa, Canada.