# Showing papers in "Earth Moon and Planets in 1988"

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TL;DR: In this paper, the characteristics of presolar dust are discussed and evidence is provided to support the possibility that presolar sand was the primary building material for the meteorites and terrestrial planets.

Abstract: The characteristics of presolar dust are discussed and evidence is provided to support the possibility that presolar dust was the primary building material for the meteorites and terrestrial planets The material in the sun's parent molecular cloud is divided into eight reservoirs The results show that presolar dust and objects made from processed dust make up the vast majority of the material in primitive chondrites The present theory is able to account for the chemical and oxygen isotopic variations between meteorite classes, the formation of chondrules, the accretion of chondrites, and parent body metamorphism

51 citations

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Brown University

^{1}TL;DR: In this paper, it is suggested that most regions of apparent low reflectivity are due to the presence of small roughness elements on the surface, and models show that the diffuse scatterers in the tessera are rock fragments originating as part of tectonic deformation of the surface.

Abstract: Pioneer Venus (PV) altimeter data have been analyzed in order to study tectonic, volcanic, and degradational processes on Venus. Analysis of a corrected reflectivity data set in combination with the PV data indicates that no more than 5 percent of the Venusian surface is covered by soils more than several to tens of cm in depth. It is suggested that most regions of apparent low reflectivity are due to the presence of small roughness elements on the surface. These regions are correlated with tessera, and models show that the diffuse scatterers in the tessera are rock fragments originating as part of tectonic deformation of the surface.

26 citations

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TL;DR: In this article, the authors derived crystal/liquid partition coefficients for Cr, V, Mn, and Fe between olivine, orthopyroxene, clinopyroxenes, and silicate melt possesing the composition of a primitive lunar green glass, at oxygen fugacities appropriate to the lunar interior.

Abstract: Crystal/liquid partition coefficients for Cr, V, Mn, and Fe have been determined experimentally between olivine, orthopyroxene, clinopyroxene and silicate melt possesing the composition of a primitive lunar green glass, at oxygen fugacities appropriate to the lunar interior. These species all behave essentially as compatible elements and possess crystal/liquid partition coefficients mostly between 0.3 and 0.9. Partition coefficients for Cr, V, and Mn are generally similar to those of Fe. This implies that crystal/liquid fractionation processes in the lunar interior which do not involve the participation of spinels would not have been effective in fractionating MnO, CrO, and VO from FeO. The well-known constancy of FeO/MnO ratios in nearly all lunar rocks is a reflection of this behaviour. It is shown that comparably strong correlations between CrO-;FeO and VO-;FeO exist for lunar highland breccias and soils from all sites and that these correlations extend to primitive lunar volcanic glasses associated with mare volcanism, strongly suggesting that the CrO/FeO and VO/FeO ratios so derived are of global importance. The observed ratios characterizing ‘differentiated’ regions of the Moon can be combined with the corresponding ratios for residual refractory portions of the Moon, using measured partition coefficients for Fe, Mg, Cr, V, and Mn between olivine, orthopyroxene and liquid. Bulk Moon abundances for Cr and V have been calculated for a range of reasonable assumptions concerning the petrogenetic relationships between differentiated portions of the Moon and complementary refractory residua consisting of olivine and orthopyroxene mineralogies. Because of the small differences in crystal liquid partition coefficients between FeO, CrO, and VO, these estimates are insensitive to large variations in the models. The bulk Moon is accordingly estimated to contain 2190–2463 ppm Cr and 79–95 ppm V. These values are very similar to the Cr and V contents of the Earth's mantle, estimated as 3010 ppm Cr and 81 ppm V by Sun (1982). The geochemical implications of these similarities are discussed.

22 citations

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TL;DR: In this paper, a detailed statistical analysis of cosmic-ray intensity data for the period 1964-1985 covering two solar cycles is performed to investigate the solar activity behaviour in relation to cosmic-rays modulation.

Abstract: Cosmic-ray intensity data for the period 1964–1985 covering two solar cycles are used to investigate the solar activity behaviour in relation to cosmic-ray modulation A detailed statistical analysis of them shows a large time-lag of about one and half years between cosmic-ray intensity and solar activity (as indicated by sunspot number, solar flares and high-speed solar-wind streams) during the 21st solar cycle appearing for a first time This lag indicates the very high activity level of this solar cycle estimating the size of the modulating region to the unambiguous value of 180 AU The account of the solar-wind speed in the 11-year variation significantly decreases the modulation region of cosmic-rays to the value of 40 AU

19 citations

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TL;DR: The main factors effective in mare ridge formation have been (i) a large areal, or maybe even global, shortening and compression, (ii) major crustal tectonics, and (iii) the moderation of tectonic movements by the megaregolith discontinuity layer(s) between surface lavas and the bedrock leaving the compressional thrust to dominate over other fault movements.

Abstract: Mare ridges of the Hesperia Planum area form linear, reticular and circular structures. The main factors effective in mare ridge formation have been (i) a large areal, or maybe even global, shortening and compression, (ii) major crustal tectonics, and (iii) the moderation of tectonic movements by the megaregolith discontinuity layer(s) between surface lavas and the bedrock leaving the compressional thrust to dominate over other fault movements in surface tectonics.

19 citations

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TL;DR: In this paper, a fixed step-size fourth-order Runge-Kutta-Gill method is employed for numerical integration of the canonical equations with Earth's oblateness.

Abstract: This paper concerns with the study of KS uniformly regular canonical elements with Earth's oblateness. These elements, ten in number, are all constant in the unperturbed motion and even in the perturbed motion, the substitution is straightforward and elementary due to the transformation laws being explicit and closed expression. By utilizing the recursion formulas of Legendre's polynomials, we are able to include any number of Earth's zonal harmonics J
n in the package and also economize the computations. A fixed step-size fourth-order Runge-Kutta-Gill method is employed for numerical integration of the canonical equations. Utilizing 5 test cases covering a large range of semimajor axis and eccentricity, we have carried out computations to study the effects of Earth's zonal harmonics (up to J
36) and integration step-size variation. Bilinear relations and energy equation are used for checking the accuracies of numerical integration. From the application point of view, the package is utilized to study the behaviour of 900 km height near-circular sun-synchronous satellite orbit over a longer duration of 220 days time (nearly 3078 revolutions) and the necessity of including more number of Earth's zonal harmonic terms is noticed. The package is also used to study the effect of higher zonal harmonics on three 900 km height near-circular orbits with inclinations of 60, 63.2, and 65 degrees, by including Earth's zonal harmonics up to J
24. The mean eccentricity (e
m) is found to have long-periods of 459.6, 6925.1 and 1077.6 days, respectively. Sharp changes in the variation of Ωm near the minima to em are noticed. The values of Ω
m are found to be very near to +-90 degrees at the extrema of em. The same orbit is employed to study the effect of variation of inclination from 0 to 180 degrees on long-period (T) of eccentricity with J
2 to J
24 terms. T is found to increase rapidly as we proceed towards the critical inclinations.

18 citations

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TL;DR: In this paper, the authors considered a large volcanic structure of about 250 km in diameter with an elevation of 5 km above the surroundings, located at the southwestern edge of Bell Regio and showed that high flexural rigidities are associated with small depressions and large thicknesses of the lithosphere and vice versa.

Abstract: Tepev Mons is a large volcanic structure of about 250 km in diameter with an elevation of 5 km above the surroundings, located at the southwestern edge of Bell Regio. It is surrounded by a moat with a depth of about 0.5 km. If this moat is considered to be caused by bending of the lithosphere due to the load of the volcano, then elastic bending models give limits for the effective flexural rigidity FR and the effective elastic thickness of the lithosphere L: 2 x 1023 Nm ≲ FR ≲ 3 x 1024 Nm and 30 km ≤ L ≤ 100 km. High flexural rigidities are associated with small depressions and large thicknesses of the lithosphere and vice versa.

16 citations

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TL;DR: In this paper, the evolution of the spin angular velocity and the obliquity β of the Venus are calculated numerically with the step-variable Runge-Kutta method of 7th order.

Abstract: By considering the torque of the bodily tides, the effect of the core-mantle viscous coupling and the torque of the atmospheric tides have been obtained by numerical calculation: the evolution of the spin angular velocity Ω♀ and the obliquity β of the Venus are calculated numerically with the step-variable Runge-Kutta method of 7th order; and 7 sets of the probable Cytherean spin evolution have been obtained. It is indicated that the present spin state of Venus is the result of long-term evolution within the reasonable ranges of some disposable parameters. The early spin period is between 7 h to 2 d and the corresponding obliquity is about 90 ° ~ 100 °. The effects of the torques of body and atmospheric tides and the core-mantle viscous coupling of Venus on its spin angular velocity could nearly cancel out each other about a billion years ago. Therefore, Venus could have been captured in a spin-orbit resonant state by the gravitational torque of the Earth on the permanent deformation part of Venus; and this resonant state has lasted up to the present time.

14 citations

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TL;DR: In this paper, the following parameters have been computed for the Cytherean atmosphere: pressure, density, speed of sound, collisional frequency, column mass, density scale, mean free-path, viscosity, pressure scale, number density at an altitude from 0 to 170 km.

Abstract: The following parameters have been computed for the Cytherean atmosphere: pressure, density, speed of sound, collisional frequency, column mass, density scale, mean-free-path, viscosity, pressure scale, mean particle velocity, number density at an altitude from 0 to 170 km.

14 citations

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TL;DR: In this paper, the authors summarized some basic age dating of a portion of the lunar surface, namely the mare in the crater Tsiolkovsky on the lunar far side.

Abstract: Although researchers in the last decade have been primarily concerned with the exotic findings of the more distant planets and moons in our solar system, as given by the Voyager series, there is still much work to be done on our nearer neighbours, including the Moon. This paper summarizes some basic age dating of a portion of the lunar surface, namely the mare in the crater Tsiolkovsky on the lunar far side.

14 citations

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TL;DR: In this article, the authors computed the secular Love and the secular tidal numbers for eight synchronously orbiting satellites in the solar system for which the triaxiality parameters and satellite-centric gravitational constant are available.

Abstract: The secular Love and the secular tidal numbers have been computed for eight synchronously orbiting satellites in the solar system for which the triaxiality parameters and satellite-centric gravitational constant are available. Excepting Deimos the total mass of which should be first refined, the secular Love and tidal numbers are rather close to unity, as a rule. That is why, the centrifugal and tidal distortions can be assumed responsible for the actual figures of the synchronously orbiting satellites resulting from the primordial spheres, as well as, their static equilibrium nearly satisfied. The hypothesis of the origin of synchronously orbiting satellites by accretion in orbits is supported by the results obtained.

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TL;DR: In this paper, the surfaces of the restricted three-body problem when the more massive body is luminous are studied and the properties of the function Ω which determines these surfaces are given.

Abstract: The surfaces of zero velocity of the restricted three-body problem when the more massive body is luminous, are studied. The properties of the function Ω which determines these surfaces are given. It is found that the topological properties of the zero velocity surfaces while not affected by the variation of the mass parameter, are essentially varied when the radiation pressure parameter changes values. Closed regions where the motion can be trapped are described while periodic motions about the “out of plane” equilibrium points seem to be probable.

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Kyoto University

^{1}TL;DR: In this paper, it was argued that the unusual activity of comet Bowell could be explained by sublimation mainly of N2 and CO in its first several approaches to the sun.

Abstract: Following the work of Whipple and Stefanik, radioactive heating by uranium, thorium and pottasium of a cometary nucleus is discussed The assumed composition is that of interstellar medium If thermal diffusivity is 10−4 cm2s−1, the central temperature of a nucleus with radius 10 km can be above 50 K, while if the thermal diffusivity is 5 × 10−3, the central temperature can be only 25 K or so Volatile gases such as N2 and CO will flow toward the outer part of the nucleus and are lost in their first several approaches to the sun This mechanism appears capable of explaining the depletion of N2 and CO relative to the interstellar abundance It is argued that unfamiliar activity of comet Bowell could be explained by sublimation mainly of N2 and CO

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TL;DR: In this article, the experimentally found variation of spectral features with particle size is discussed in terms of photon's mean free path and its dependence on particle size in the wavelength regions characterized by normal and anomalous dispersion, respectively.

Abstract: Measurements of spectral emittance at wavelengths from 5 to 25 Μm were carried out for various particulate rocks and minerals (granite, calcite, talk) in dependence on particle size. The experimentally found variation of spectral features with particle size is discussed in terms of photon's mean free path and its dependence on particle size in the wavelength regions characterized by normal and anomalous dispersion, respectively. Moreover, a sample consisting of fine- and coarse-grained material was investigated in order to estimate the chance for mineral identification at conditions relevant to remote sensing of planetary objects. The mixture spectrum comprises characteristic features of both grain size fractions. This implies that the mineralogical composition of the fine-grained fraction also should be accessible by use of high-sensitive spectrometers.

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TL;DR: In this paper, the velocity dependent coefficient of restitution, α = α(Ν), was shown to lead to a many particle thick equilibrium state, independent of the initial conditions, and the essential requirement for this to take place is that dα dΝ 0, the system either disperses through growing random velocities, or flattens to a near monolayer state.

Abstract: Numerical simulations of 250 mutually colliding particles, revolving in the gravitational field of a central body, indicate that velocity dependent coefficient of restitution, α = α(Ν), can lead to a many particle thick equilibrium state, independent of the initial conditions. The essential requirement for this to take place is that dα dΝ 0, the system either disperses through growing random velocities, or flattens to a near monolayer state, depending on the initial conditions.

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TL;DR: The numerous problems related to the origin and evolution of Phobos and Deimos, as well as specific features of their topography, are readily accounted for in the context of a concept presupposing the possibility of detonation (or burning) of electrolyzed ices as mentioned in this paper.

Abstract: The numerous problems related to the origin and evolution of Phobos and Deimos, as well as to specific features of their topography, are readily accounted for in the context of a concept presupposing the possibility of detonation (or burning) of electrolyzed ices.

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TL;DR: In this article, the authors show that the velocity and temperature of the gas escaping from the nucleus over the theoretical values, the outflow being concentrated in several ( ~ 12-15) narrow ( ~ 300 m in size at the nucleus) hypersonic jets carrying very large amounts of remarkably fine CHON dust and located along continuous lines on the nuclear surface, intense release from either the nucleus or very close to it (≲2 × 103km) of CO (QCo/QH2O = 0.05-0.2) with a smaller amount of CO

Abstract: The totality of the results obtained in the VEGA, GIOTTO and SUISEI projects does not lend itself to interpretation within the old sublimation models of comet activity considering solar radiation as the sole source of energy. Among them are the systematic excess of the velocity and temperature of the gas escaping from the nucleus over the theoretical values, the outflow being concentrated in several ( ~ 12–15) narrow ( ~ 300 m in size at the nucleus) hypersonic jets carrying very large amounts of remarkably fine CHON dust and located along continuous lines on the nuclear surface, intense release from the nucleus or very close to it (≲2 × 103km) of CO (QCo/QH2O = 0.05–0.2) with a smaller amount of CO2 (QCO2/ QH2O ≈ 0.015), large near-nucleus abundances of C, C+ (QC/QCO ≈ 0.29), etc.

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TL;DR: In this paper, a review of certain lunar features with specific regard to those found in the crater Tsiolkovsky is presented, with a focus on the impact of gravity on the terrain.

Abstract: This paper is a review of certain lunar features with specific regard to those found in the crater Tsiolkovsky.

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TL;DR: In this article, it was shown that pure chance or random processes only cannot explain the planetary and satellite distance distributions, in particular the exponential spacings, by comparing the distance relations of real systems to these of planetary-like systems generated at random.

Abstract: It is often thought that the exponential distance relations that can be found amongst the distances of the planets and of the satellites of Jupiter, Saturn, and Uranus, of the form an = αβn, with an being the semi-major axis of the nth body, can be similarly represented by sequences of sorted random numbers generated with some constraints corresponding to certain physical processes. We give in this paper some indications showing that pure chance or random processes only cannot explain the planetary and satellite distance distributions, in particular the exponential spacings, by comparing the distance relations of the real systems to these of planetary-like systems generated at random.

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TL;DR: Spectrophotometric observations of the head of comet Bradfield (1987s) during three nights in 1987 are presented in this paper, where an estimate of the CN, C2, and C3 column densities and production rates have been made.

Abstract: Spectrophotometric observations of head of comet Bradfield (1987s) during three nights in 1987 are presented. An estimate of the CN, C
2, and C
3 column densities and production rates have been made.

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TL;DR: Geomagnetic virtual pole positions (VGP's) calculated from archaeomagnetic directional data are compared with three ancient accounts of low latitude observations of the Aurorae boreales, viz by Aristotle (384-322 BC), Seneca (55 BC-40 AD) and simultaneously by Chinese astronomers in Hangzhou, China and by European observers in Prague in 1138 AD, October 13th as discussed by the authors.

Abstract: Geomagnetic virtual pole positions (VGP's) calculated from archaeomagnetic directional data are compared with three ancient accounts of low latitude observations of the Aurorae boreales, viz by Aristotle (384–322 BC), Seneca (55 BC-40 AD) and simultaneously by Chinese astronomers in Hangzhou, China and by European observers in Prague in 1138 AD, October 13th

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Cairo University

^{1}TL;DR: In this article, a special perturbation technique of Encke-type associated with the KS regularized variables was developed for satellite motions in the Earth's gravitational field with axial symmetry.

Abstract: In this paper of the series, a special perturbation technique of Encke-type associated with the KS regularized variables will be developed for satellite motions in the Earth's gravitational field with axial symmetry. Its computational algorithm is of recursive nature and could be applied for any perturbed conic motion whatever the number of the zonal harmonic coefficients may be. Applications of the algorithm are also included.

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TL;DR: In this article, the authors made an attempt to not only review but reopen the debate on non-linear meteor trails, and found that approximately one in every two hundred of the visual meteors is likely to show a nonlinear trail, and that of such trails about 60% will be continuously curved and 40% sinusoidal.

Abstract: In this essay an attempt is made to not only review but reopen the debate on non-linear meteor trails. On the basis of data culled from various, now historical, sources it is found that approximately one in every two hundred of the visual meteors is likely to show a non-linear trail, and that of such trails about 60% will be continuously curved and 40% sinusoidal. It is suggested that two mechanisms may explain the various trail types: the continuously curved trails being a manifestation of the classical Magnus effect, and the sinusoidal trails resulting from torque-free precession.

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TL;DR: In this paper, the authors derived a criterion for gravitational instability in a gaseous medium for particulate discs, in which the equilibrium depends on the collisional energy loss, and used it to predict the formation of highly elongated clouds with a relatively long lifetime before decay.

Abstract: Collisionally-induced amplification of density fluctuations can also produce non-axisymmetric local condensations in particulate discs if the optical thickness is between definite values. Gravitational instability occurs above this interval. The theory of both phenomena is derived from collisional equations. The conventional criterion for gravitational instability in a gaseous medium cannot be used for particulate discs, in which the equilibrium depends on the collisional energy loss. These instabilities can produce an unbounded growth in density or a gravitational coagulation of particles, but the typical consequence is the formation of highly elongated clouds which are denser than the background matter and have a relatively long lifetime before decay. The third type of instability, the thermal one, appears at low values of velocity dispersion. It only affects the random motion of particles without producing condensations.

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TL;DR: In this paper, the infrared brightness of a flattened comet belt beyond the orbit of Neptune using a disk-like model with a power-law density distribution of comets was investigated and compared with the emission from a model zodiacal dust cloud in the ecliptic and with published IRAS data.

Abstract: We consider the infrared brightness of a flattened comet belt beyond the orbit of Neptune using a disk-like model with a power-law density distribution of comets. We compare this spectrum with the emission from a model zodiacal dust cloud in the ecliptic and with published IRAS data and present some consequences of dust in the comet belt.

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TL;DR: In this article, the dynamical flattening of the Earth and the Moon is derived based on the resonance rotation theory, and the results of the method derived from the observed value of the Mercury's obliquity θ are analyzed.

Abstract: The method which is used to calculate the dynamical flattenings % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXafv3ySLgzGmvETj2BSbqefm0B1jxALjhiov2D% aebbfv3ySLgzGueE0jxyaibaiiYdd9qrFfea0dXdf9vqai-hEir8Ve% ea0de9qq-hbrpepeea0db9q8as0-LqLs-Jirpepeea0-as0Fb9pgea% 0lrP0xe9Fve9Fve9qapdbaqaaeGacaGaaiaabeqaamaabaabcaGcba% Gaamisaiabg2da9iaacIcacaWGdbGaeyOeI0YaaSaaaeaacaaIXaaa% baGaaGOmaaaacaGGOaGaamyqaiabgUcaRiaadkeacaGGPaGaaiykai% aac+cacaWGdbaaaa!4717!\[H = (C - \frac{1}{2}(A + B))/C\] of the Earth and Moon meets with difficulties when it applies to Mercury and Venus. In this paper, after the calculation of the dimensionless moment of inertiaC/MR
2 by solving the Emden equation, the effectiveness of the method deriving dynamical flattening from the observed value of the Mercury's obliquity θ is analysed based on the resonance rotation theory. Some suggestions are made for the future space explorations. Finally, the ranges of dynamical flattening and of the obliquity of Venus are calculated.

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TL;DR: The Alba Patera main graben zone is radial to the Tharsis bulge, indicating the importance of the tharsis-related peripheral rift tectonics.

Abstract: The Alba Patera main graben zone is radial to the Tharsis bulge, indicating the importance of the Tharsis bulge-related peripheral rift tectonics. The concentric grabens around the Alba Patera area are also partly caused by crustal bending due to the central load of the Alba Patera volcano. These two graben sets partly coincide forming composite structures. Both tectonic systems were still active after the last major volcanic lava extrusions took place. After this, the crater chain grabens, radial to the northernmost part of the Tharsis bulge were formed. These collapse craters were evidently caused by the late-tectonic forces due to the northern Tharsis and adjoining lava loads, resulting in flexural tension and activating previous faults.

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TL;DR: In this article, a model with varying contributions from bacterial-type and viral-type particles, and with small additional contributions arising from degraded organic molecules at grain surfaces, is presented.

Abstract: Infrared observations of comets over the 2–4 Μm waveband are interpreted in terms of a model with varying contributions from bacterial-type and viral-type particles, and with small additional contributions arising from degraded organic molecules at grain surfaces.

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TL;DR: In this article, it was shown that the required order of magnitude of angular momentum from the Sun to the planetary system can be transferred by another mechanism based on the principle of inertial induction.

Abstract: Transfer of angular momentum from the Sun to the planetary system has been found to be inevitable in all evolutionary models for the origin of the solar system. In ‘cold’ theories it has been proposed to be achieved through friction whereas electromagnetic forces are considered to be the agent for this transfer in ‘hot’ theories. In the present paper it has been shown that the required order of magnitude of angular momentum can be transferred by another mechanism based on the principle of inertial induction. In the previous theories most of the transfer had been assumed to have taken place during the pre-Main-Sequence period whereas in this proposed theory most of the transfer takes place during the Main-Sequence period of the Sun. The paper does not intend to go into the details of planet formation and the evolutionary process but confines itself only to the problem of angular momentum transfer.

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TL;DR: In this article, the authors used the shape-from-shading (SDF) literature to evaluate the stability of the surface integral approach to radar image synthesis and showed that the value of the SDF approach is much in doubt.

Abstract: Because radarclinometry is fundamentally describable in terms of a nonlinear, first-order, partial differential equation, one expects that it can, in principle, be carried out by direct deterministic integration beginning at a given threshold profile along the azimuthal coordinate. Such a boundary condition could be provided by the altimetry profile obtained on a preceding or succeeding orbital revolution of the radar-bearing spacecraft. Notwithstanding the mismatched resolutions of the radar altimeter and the radar imaging system as planned for the Megallan mission to Venus, there are fundamental considerations, not involving system noise, that influence the possibility of success of this approach. From the topographic map of the Lake Champlain West quadrangle in the Adirondack Mountains of the U.S., a radar image is synthesized. Radarclinometry, in surface integral form, recaptures the topographic map when the applicable radar reflectance function is weakly variable over the range of application, but it diverges beyond a certain point for nominally variable reflectance functions. The effect can be understood by using results from the “shape-from-shading” literature. (This literature is produced by a group within the artificial intelligence community who have been independently attacking, for all practical purposes, photoclinometry, except that they have not given primacy to images of terrain.) The ubiquity of the instability suggests that the value of the surface integral approach is much in doubt.