Icarus
Orbital evolution of protoplanets embedded in a swarm of planetesimals has been investigated to study the late stage of planetary formation when protoplanets suffer perturbations among themselves and dynamical friction by surrounding planetesimals. We investigated the orbital evolution through direct three-dimensional N-body simulations. We found that the orbital separation between two protoplanets...
CCD photometry performed on the comet/asteroid transition object 4015 Wilson-Harrington during its most recent apparition has provided a new rotational lightcurve with a standard double-peaked rotational period of 6.1 +/- 0.05 hr and an amplitude of 0.2 magnitudes. The size, rotation period, and lightcurve amplitude of this object are all similar to values found for near-earth asteroids (NEA) and...
We present a self-consistent computation of the structure of the dust subdisk in the protoplanetary nebula. The main physical processes governing the dynamics of the dust disk are reviewed. A (nonlinear) vertical diffusion equation for the transport of dust particles is derived. It is based on a competition between sedimentation processes due to gravity and diffusion due to turbulence. The vertical...
Radio occultation experiments were conducted at Venus on three consecutive orbits of the Magellan spacecraft in October 1991. Each occultation occurred over the same topography (67 o N, 127 o E) and at the same local time (22 h 5 m ), but the data are sensitive to zonal variations because the atmosphere rotates significantly during one orbit. Through comparisons between...
Schmider et al. (Schmider, F.-X., B. Mosser, and E. Fossat 1991. Astron. Astrophy. 248, 281-291) and Mosser et al. (Mosser, B., D. Mekarnia, J.P. Maillard, J. Gay, D. Gautier, and P. Delache 1993. Astron. Astrophys. 267, 604-622) report detection of Doppler shifts in reflected solar radiation from Jupiter purportedly induced by p-mode oscillations of the planet. We consider the possibility that these...
Using Viking Orbiter images, detailed photoclinometric profiles were obtained across 10 irregular depressions, 32 fretted fractures, 49 troughs and pits, 124 solitary scarps, and 370 simple grabens in the north Tharsis region of Mars. These data allow inferences to be made on the shallow crustal structure of this region. The frequency modes of measured scarp heights correspond with previous general...
We calculated the vapor flux of the icy components in the surface layer of a porous, short-period, Jupiter-class comet, in order to investigate the relationship of the observed relative molecular abundances in the coma with those in the nucleus. The model assumes a body containing one major ice component (H 2 O) and up to three minor components of higher volatility (e.g., CO, CO 2 ...
Periodic comet Swift-Tuttle is the largest known object in the Solar System whose current orbit allows it to make repeated close approaches to the Earth. As such it poses a significant impact hazard. In addition, P/Swift-Tuttle possesses the second longest observing are of any comet, with recorded observations spanning two millennia. These data place extremely tight constraints on the current orbit...
The evolution of the emission spectrum of C 2 molecules (Swan bands (0,0) and (1,1)) was studied with two different methods in two different comets: P/Schaumasse and P/Tempel 2. Comet P/Schaumasse was observed in February 1993 in imagery mode with the 1.20-m telescope of the Observatory of Haute-Provence (France). Three different interference filters were used, centered at 5125, 5160, and...
An axisymmetric time-dependent cloud model with dynamics and detailed microphysics of Jupiter's water cumulus clouds is presented. The microphysical processes operating in these clouds are analyzed and compared to those of terrestrial clouds. Diffusional growth and coagulation of water drops and ice crystals were found to be faster and more efficient in Jupiter. Large particles were formed on short...
Our present paradigm of the formation of stars and planetary systems suggests that the early Solar System may have existed in much denser environments than the galactic disk, e.g., the cores of giant molecular clouds and open stellar clusters. Some constraints on a hypothetical primordial environment can be inferred from the present dynamical state of the Sun and planets. Tremaine (1991, Icarus 89,...
A new analytic solution for the limit of weak solar radiation pressure force acting on dust particles around a spherical body in an eccentric orbit (e.g., comet) is presented. The closed solution of this radiation pressure approximation, here called RPA, is remarkably simple. The components of the orbital angular momentum vector of a dust particle and the components of an auxiliary vector, both projected...
The observed magnetism of asteroids such as Gaspra and Ida (and other small bodies in the solar system including the Moon and meteorites) may have resulted from an impact-induced shock wave producing a thermodynamic state in which iron-nickel alloy, dispersed in a silicate matrix, is driven from the usual low-temperature, low-pressure, α, kaemacite, phase to the paramagnetic, ε (hcp), phase. The magnetization...
We have analyzed nine Voyager 1 infrared spectral averages covering Titan's disk from 53°S to 70°N. By use of radiative transfer modeling we have determined the thermal profiles and mean molecular abundances in the stratosphere of the species with signatures in the region 200-1500 cm -1 . Temperature latitudinal variations were found in accordance with Flasar and Conrath (1990, Icarus 85,...
The spectral characterization of small asteroids is important for understanding the evolution of their compositional and mineralogical properties. We report the results of a CCD spectroscopic survey of small main-belt asteroids which we call the Small Main-belt Asteroid Spectroscopic Survey (SMASS). Spectra of 316 asteroids were obtained, with wavelength coverage ranging from 4000 to 10000 Å (0.4...
We present a rudimentary theoretical assessment of electrical discharge heating as a candidate mechanism for the formation of chondrules in the solar nebula. The discharge model combines estimates of the properties of the nebula, a mechanism for terrestrial thunderstorm electrification, and some fundamental electrical properties of gases. Large uncertainties in the model inputs limit these calculations...
We observed theJ(2-1) and (1-0) lines of CO in Comet P/Schwassmann-Wachmann 1 with high spectral resolution at four different epochs. The line profile is dominated by a very narrow (0.14 km sec -1 FWHM) component blueshifted by 0.48 km sec -1 , with a fainter component redshifted at 0.30 km sec -1 . We infer the kinematics of the coma, cold (≃10 K) kinetic and rotational temperatures,...
Asteroid 2953 Vysheslavia, a Koronis family member about 15 km in diameter, very close to the outer edge of the 5/2 Kirkwood gap, has been shown by numerical integrations to fall into the resonance; then it approaches Jupiter and ends up into a hyperbolic orbit. The typical dynamical lifetime is of the order of 10 Myr. This "marginally unstable" region of the orbital element space bordering...