[en] Infrared emission from a planet at a very small angular separation from its star offers the possibility for detection by interferometry from space. However it has been suggested that attention should be paid to interference produced by the infrared radiation that would be generated within the space package by cosmic ray protons. Quantitative examination reveals that both the primary Cerenkov flux and the secondary infrared emission from Cerenkov heating are negligible. (Auth.)

[en] It is shown by linear stability analysis that a preplanetary (presatellite) disk of dust and gas with Keplerian velocity field can become unstable due to the collective self-gravity of the disk. The radial distribution of rings, which may result from this instability, is derived. These rings later on can be the formation sites for planets around the Sun and for satellites around the planets. The derived orbits are shown to be in good agreement with that of the planets and the satellites (of Jupiter, Saturn, and Uranus). Predictions and conclusions seem to be possible for the existence of three yet unknown Uranian satellites, the origin of the early Moon and the possible radial extension of the planetary system. (Auth.)

[en] Maxima of calculated topographical line-of-sight (LOS) gravity attractions caused by Ishtar Terra are shifted to the north with respect to the measured LOS free air gravity maxima south of the highland. This implies a tendency to isostatic compensation of central Ishtar and mass surpluses at the continental border and the southern forelands. The authors present a scenario compatible with the interpretation of the gravity anomalies and morphological features. The existence of global plate tectonics on Venus like on Earth is not necessarily implied, but at least limited horizontal movements of the Venusian lithosphere seem to be likely. This result shows that plate recycling must be considered for heat transfer through the lithosphere beside conduction and hot spot volcanism. (Auth.)

[en] Dynamic spectra of Jupiter's decametric emission often display narrow-band features, referred to as events of type N. The average bandwidth of these emissions is in the vicinity of 200 kHz, their durations are typically in the decasecond range, and their f-t slopes are small and random. Although the N-bursts can be described as narrow-band L-bursts, it seems that they are related to S-bursts in their area of occurrence in the Io-B region, the durations of the emission envelopes, and their bandwidths. Possible implications are discussed. (Auth.)

[en] Stars usually form as members of binary or multiple star systems, and it is likely that the Sun was no exception. The mass and position of possible past companions of the Sun is determined by considering the orbital stability of the Solar System. This is achieved by considering the stability of critical three-body subsets comprising the sun-planet-companion star which must be stable if the Solar System is to remain stable as a whole. (Auth.)

[en] A new approach to the study of future dynamical evolution of the Neptune-Triton system is presented. After the analytical development of the model, the final results are compared with those drawn by previous works on the same subject. (Auth.)

[en] Conditions for the formation of a large gaseous protoearth and the formation of a satellite are considered. The energy required is assumed to come from the gravitational contraction to form the Sun, the contraction to form the protoearth, core overturn and planetesimal impacts on the protoearth. The model is compatible with geochemical, tidal and angular momentum data. (Auth.)

[en] The concept of Roche limit is applied to the Laplacian theory of the origin of the solar system to study the contraction of a spherical gas cloud (solar nebula). In the process of contraction of the solar nebula, it is assumed that the phenomenon of supersonic turbulent convection is operative and brings about the halt at various stages of contraction. It is found that the radius of the contracting solar nebula follows the Titius-Bode law. The consequences of the relation are also discussed. The aim is to attempt to explain, on the basis of the concept of Roche limit, the distribution of planets in the solar system and try to understand the physics underlying it. (Auth.)

[en] Corotating solar wind streams emanating from stable coronal structures provide an unique opportunity to compare the response of planetary ionospheres to the energy conveyed in the streams. For recurrent solar conditions the 'signal' propagating outward along spiral paths in interplanetary space can at times exhibit rather similar content at quite different downstream locations in the ecliptic plane. Using solar wind measurements from plasma detectors on ISEE-3, Pioneer Venus Orbiter (PVO) and Helios-A, as well as in-situ ion composition measurements from Bennett Ion Mass Spectrometers on the Atmosphere Explorer-E and PVO spacecraft, corotating stream interactions are examined at Earth and Venus. (Auth.)

[en] Space exploration has changed our views not only on the properties of celestial bodies and the interplanetary medium but also our perspective on the formation of such bodies, including the Earth. However, on few points do the new hetegonic insights approach certainty. More appropriately, they can be said to raise physically meaningful questions and to decrease the degrees of freedom allowable in any given scenario, which necessarily extends into the early history of the planetary crust, ocean and atmosphere. An attempt is made here to outline the basic schemes envisaged in modern studies of the origin of the Earth and the ramification of consequences for its early evolution that currently appear allowable and supported by observation. (Auth.)